: cheap power improvements to the 425...



Night Wolf
10-06-04, 01:09 AM
Since I decided to push the build up on the 425 out of line for this winter project (NorthStar took it's place) I was thinking what I could do to get a little more power from the beast....

my first thoguht is the cat... it's gotta go... my father mentioend something about thee first gen cats having a "drain plug" that you can take out, and the beads inside fall out, kinda like gutting the cat? On his '79 Coupe, he had a test pipe on it.. but I can't seem to find them anymore.... I don't think I could take it to a shop , even though it is now over 25 years old, and there is no emmisions testing... so what would the best thing seem to be?

While under the car, the whole exhuast system seems to be restriced... especailly all the bends going over the rear axel... what is this, 2.5" piping (my 4.9 has 2.5") but I am not messing with the exhaust system now... I was thinking maybe a cheap after market muffler... might flow better? something like $40 or something? also give it a nice tone... but not too loud... would I even benifit form that? or just keep what it has.... Also the resonator... from what i coudl find out, they don't seem to restric the flow of exhaust at all.. do they?

Then it would be some sort of an intake... I bought, and tired to fit a 14" open element on it, but it hit the AC compressor... somebody menitoend about a 1" spacer? should I do that or see if a 9" kit will work (but probably look bad)... also would I gain anything from the open element over the factory air cleaner assembly?

the tune-up I first did on it consisted of:

new air filter
new fuel filter
new spark plugs
oil change

I suppose I should rrepalce the cap&rotor and wires also... just for the extra touch, and maybe even the plugs, although they are new... they are basic AC Delco, $2/each... nothing special (platnium, double tipped etc...) do you think they are ok to keep in there? should I replace the cap/rotor and wires, or leave them? the wires are 8mm Whitiker....

What else can I do for a tune up? I know my carb needs to be rebuilt as it acts funny when the enigne is cold... anything to restore some power?

I do need to change the coolant, as it is really ugly... but that really isn't anything for performance...

my AC dosn't work (leak in the lines) no big deal, but should i remove the AC belt... less rotating mass?

Abotut he carb... here are the problems... when the enigne is cold.. after I first started it, if in park I put my foot to the floor for a second.. it'll sputter, run rough and want t quit... if i drive it.. there is an off-idel dead spot where it'll shutter and have a hard time accelerating, and if the engine is cold enough.... stall out... also until the engine has fully warmed up, if I try to floor it... well, to the point where the secondaires would normally start to open... when it gets to that point, the enigne looses alot of power, the car shakes and shutters, engine RPM really dosn't build, it may back fire, then depenging on how warm the enigne is, either rev up in RPM like normal, or just keep doing that.... maybe a problem witht he secondaires?

Everythign else with the carb is fine, when the engine warms up, there is no delay or anything, runs great... if it hasn't been ran for a day or 2, a cold start can be hard.. I heard all Q-jets have a drip down problem? I pump the gas 3 times, crank it, stop, pump twice then crnak and it'll start... although when warm, it'll start up within a split second of turning the key...

Maybe if the carb is out of adjustment, and I fix it, that coudl improve power and gas millage.... IIRC my father said the caps on the adjustments have been removed, so it is adjustable now...

I am just looking for some cheap ways to tya nd improve the power a little... I know the enigne isn't running how it hould be (well, have the power it should... she runs nice) so maybe I can get some help from the crew :)

mastertech
10-06-04, 10:25 AM
I had a similar problem with my 425... The carb probably does need an overhaul, not very much trouble if you are mechanically inclined...the accelerator pump seal you will probably find dry rotted, causing that hesitation, and these fuel pumps have a problem with a check ball to return excess fuel at idle... you should probably throw one of those on, too...they run about $35...also be sure to clean the secondary rods when you have it apart! Let us know how it goes!

Night Wolf
10-07-04, 05:09 PM
anything?

davesdeville
10-07-04, 08:22 PM
my first thoguht is the cat... it's gotta go... my father mentioend something about thee first gen cats having a "drain plug" that you can take out, and the beads inside fall out, kinda like gutting the cat? On his '79 Coupe, he had a test pipe on it.. but I can't seem to find them anymore.... I don't think I could take it to a shop , even though it is now over 25 years old, and there is no emmisions testing... so what would the best thing seem to be?:)

There's about a 2" plug on the bottom of the cat. It's a pain in the ass to get it out, and if you can get it out there's a good chance you'll have deformed it so it won't go back in there. If you know someone with a welder you can just weld some sheet metal over the hole. I did this a few weeks ago and it did seem to make a good differance. I left the hole open for awhile and it was pretty loud...

Night Wolf
10-07-04, 09:07 PM
I was thinking about going ot the local Midas, and saying that the car is over 25 years old, no emmissions testing etc... if they can cut the cat out and put a stright pipe in it.... if he says no, I'll ask about slipping him a $20...

Did it make a nice difference? I would imagine it helping, as the whole exhaust system seems to be restrictive...

... what about using JB Weld to keep a piece of aluminam over the hole?

Also, when you pulled the plug, did the beads just drain, did you have to shake it etc....?

lux hauler
10-07-04, 09:14 PM
Chances are, a "chain-type" muffler shop isn't going to touch it. I've heard there are big fines if they're caught. Best bet would be to find a small local shop or just buy the stuff and do it your self.

Dead Sled
10-07-04, 09:33 PM
Chances are, a "chain-type" muffler shop isn't going to touch it. I've heard there are big fines if they're caught. Best bet would be to find a small local shop or just buy the stuff and do it your self.

most will make you sign and offroad use only waiver

but agree start with exhaust make it flow then intake make it flow. the easier you can make air move in an engine the more power you can make

davesdeville
10-07-04, 11:02 PM
Did it make a nice difference? I would imagine it helping, as the whole exhaust system seems to be restrictive...

... what about using JB Weld to keep a piece of aluminam over the hole?

Also, when you pulled the plug, did the beads just drain, did you have to shake it etc....?

It did for me - but then again my FW was in pretty bad shape and had run real rich for awhile, so the beads were fairly clogged with carbon. Cats get pretty hot, I'm not sure how well JB weld would hold up under several hundred degrees. I put a paper bag under the hole, the beads took their time to come out, I used a rubber mallet to help them along.

Night Wolf
10-08-04, 03:20 AM
well, I am not looking to spend alot of money for this.. but besides dumping the cat, what else could I do to free up the exhaust? the piping dosn't look too big, but I am not replacing it, as mine is fine... that leaves the muffel and the resonator...

..for intake, maybe I'll try the spacer and get the 14" open element again... I really don't want to spend *alot* of money into the 425 (yet) but just something to make it a little more snappy....

that is true with the chain stores.. there is a local private shop that does exhaust work,t he kid goes ot my school... the only thing i owrry aobut is, they beat the hell out of cars.. customers cars, cars they sell on the lot etc... so I suppose I could just wait there and make sure thing bad happens... I know they woudl do it too...

Night Wolf
10-08-04, 03:22 AM
I notice sometimes after running the enigne, or is I stand outside the car while it is running, the exhaust will smell like rotten eggs.... mixture too rich?

Should I bother to replace the cap+rotor, and wires, or no... also are the basic AD Delco plugs good enough for the job for now? they are practically brand new...

davesdeville
10-08-04, 05:23 AM
The rotten egg smell may be indicative of a cat that's already going bad. It might go away after the catalyst beads are gone.

My friend had some exhaust tubing and a perfectly good chrome tip so we cut off the resonator and replaced it with that. It didn't change the sound at all but I never took it on the freeway to see if it increased the drone.

Take a look at the cap and rotor and if any contacts don't look good replace. The plugs should be OK, I mean it won't hurt to change them but it won't do much good. At least visually inspect the wires for cracks, and take a look at them in the dark with it running, if you see any electricity 'leaking' from them it's time for some new wires.

Night Wolf
10-08-04, 12:31 PM
hmm, maybe the cat is starting to go... only (almost) 86k, but it is 25 years old....

... the only wear point on the cap was where the finger touches the metal plate.. my father said it is in pretty good shape... no cracks on the wires, nothing strange at night either.... I never heard of the brand... Whitiker (sp?)they are orane and 8mm....

cadillacdeville
10-13-04, 02:49 AM
if you wanted to remove the cat you could try getting a couple of 2 and1/2 to 3" clamps along with about 18" peice of pipe and cut that cat off and clamp the pipe on tighten it down should work fine also I replaced my muffler a while ago as the weld had totaly rusted away with a turbo muffler from dynomax but its 3" very open almost straight through sounds excelent with a good low rumble until the secondarys open then it gets loud very loud muffler was only round 40 to 50$ definitly improved the acceleration also replace that cap and ignition coil in there I replaced my cap with one from acdelco along with a ignition coil form acdelco with 8mm wires and plantnum bosch plugs all for under about 60 or 70$ the plugs i think were the most expensive plus get that 14" air cleaner you'll need to get some eltra spacer peices and longer stud but that stock air cleaner has an opening of about 4" whereas the edelbrock is 14" round and 3"high and will definitly let her breath in a lot better also look in to replaceing that carb ABC gets a performance rebuild
Q-jet from a place in california cost around 250$ but works wonders over the factory carb

7.0,hellyeah
10-14-04, 01:07 AM
As far as all of this exhaust talk goes, it gave me loads of powr just ripping everything off after the cat. It keeps it quiet enough that police won't immedietly cry no exhaust but it gives the car more snap. The 14"X3" will only take in loads of hot air. Get a later models fuel injection air intake assembly. That will be able to handle a 14X3 K&N and it will get you cold air from the front of the car. No riser is needed either. If you do use the 14X3 assemply and riser make sure to plug the vacuum tube coming out of the original assembly. That caused me really bad timing problems later on. Dist. coils give good power too.

abcdefg
10-15-04, 09:59 PM
My cadillacs 1977 425 is a gutless wonder. Im amazed at how i "cruise" up hills in this thing. With the gas pedal about 3/4 on the floor (in 2nd gear going 20mph) it barely holds its speed, and this is a fairly new engine.

When i put it in Low and "floor it" its pretty good untill about 25-30 then its like im towing a school bus behind me, it accelerates faster in 2nd after that than it does in 1st. I busted out my cadillacs service manual, and looking at a cutaway view doesnt give me a suprise as to why this engine is neutered on the top end.

The intake manifold looks like a snake, you can even see the tight bends just by popping your hood.

I do have a muffler and exhaust tip off a 12 liter kennworth diesel, but i think the caddy would drag bottom with either thing. Plus i dont want it to look like a "ricer" (5" 4.5 foot long chromed pipe hanging out)

The easiest route to go would have been to buy that 500 cid on ebay. It had a blower, 8 port nitrous fogger, heavy duty performace connecting rods pistons and all, hot valve cam... but i dont want to blow up my THM400...


Is the 425 cid really this wimpy?


If im lucky enough to find a 425cid or 500cid caddy with fuel injection, and figured out how to hotwire it into my carbureted wiring, would this give it more balls at the top end (past 2000rpm)? I see the fuel injected deville is rated at 190hp, versus the carbureted 180hp. I suppose a die grinder and carefull planning would give the fuel injected manifold more oomph?

Dead Sled
10-16-04, 09:35 PM
My cadillacs 1977 425 is a gutless wonder. Im amazed at how i "cruise" up hills in this thing. With the gas pedal about 3/4 on the floor (in 2nd gear going 20mph) it barely holds its speed, and this is a fairly new engine.

When i put it in Low and "floor it" its pretty good untill about 25-30 then its like im towing a school bus behind me, it accelerates faster in 2nd after that than it does in 1st. I busted out my cadillacs service manual, and looking at a cutaway view doesnt give me a suprise as to why this engine is neutered on the top end.

The intake manifold looks like a snake, you can even see the tight bends just by popping your hood.

I do have a muffler and exhaust tip off a 12 liter kennworth diesel, but i think the caddy would drag bottom with either thing. Plus i dont want it to look like a "ricer" (5" 4.5 foot long chromed pipe hanging out)

The easiest route to go would have been to buy that 500 cid on ebay. It had a blower, 8 port nitrous fogger, heavy duty performace connecting rods pistons and all, hot valve cam... but i dont want to blow up my THM400...


Is the 425 cid really this wimpy?


If im lucky enough to find a 425cid or 500cid caddy with fuel injection, and figured out how to hotwire it into my carbureted wiring, would this give it more balls at the top end (past 2000rpm)? I see the fuel injected deville is rated at 190hp, versus the carbureted 180hp. I suppose a die grinder and carefull planning would give the fuel injected manifold more oomph?


start with little things first the 425 isn't really that bad just needs a little help breathing. make th eintake and exhaust flow. things like a hotter coil and ignition advance kit for the dizzy good plugs and wires. small things like this will really liven it up. cad motors arent a high revving motor like chevys or fords. Cads are a torque motor you may only have 190 horse but the torque more than makes up for it.

how your tranny doing? color and smell of fluid, when was it changed. its hard to blow a trubo 400 but you may be

lux hauler
10-16-04, 10:12 PM
abcdefg,
Sounds to me like you need some tuning. As dead sled said, the 425 is not that bad an engine....if it's tuned right.
Remember....these engines are designed to make their power at lower rpm's. If your looking for an engine that'll pull to 5500 or 6000 rpm's with factory parts, you don't need a big block caddy. Stock....4000-4400 and these things are done. That's the way they were designed.....low rpm torque.

abcdefg
10-18-04, 01:03 AM
im not looking for a high revving motor. I need a motor for crusing in, and i've already had everything checked on it. My exhaust finnaly fell off (whole 8 feet after the catalytic converter) so i ripped it out and drive it with the pointed peice out of the back of the converter. It now can do a U-turn where it wouldnt before (some help from spinning the tires). But it still doesnt have what it takes at the low end to move this car from stop signs and up hills.

What i meant about the THM400, i didnt think it would hold out to a supercharged 500cid with nitrous. I will unhook the catalytic converter when i repair the exhaust, and see if that helps the bottom end.

How would further advancing the timing help? im running 18DBTDC, and with vaccume advace it should be at least 22-24 degrees. The whole engine looks like it will jump out of its engine mounts from the timing. And it does drive more sluggish with less advance.

7.0,hellyeah
10-18-04, 08:48 PM
It aint made for high end at all. A good exhaust system wouldn't be bad for the thing either. Torque comes from massive intake and low exhaust outlet. Fabricating bigger exhaust manifolds would make it awsome. New intake manifold too. Those two things and the car would run like a champ! The 472 is a much better engine, I'm sorry to say that though as an owner of a 425.

davesdeville
10-18-04, 09:58 PM
You want more power, bolt on an Edelbrock and some headers and a big enough exhaust system to handle it. As for timing, the big brothers of the 425s seem to like 10-12* initial, 32-34* advanced, the 425s are probably similar.

7.0,hellyeah
10-19-04, 03:40 PM
Slapping on 472 intake manifolds will give more power right, more high end I least I thought. Will the 472 manifolds bolt right on or do they need to get ported?

abcdefg
10-25-04, 10:51 PM
I got it up on the highway with only the catalytic converter for exaust. It probably has enough power to pass someone, but once it hits about 50 its just about dead, then it shifts into 2nd somewhere near 60. The 425 just does not have what it takes to move an areodynamically challenged 2 1/2 ton car at 60mph up hills.

I can get ahold of a 472/500cid intake manifold. Im sure my current gaskets will be trashed if i take the 425 manifold off, so if it will make enough difference to make me want to spend money on gastkets, sure...

What about a bigger air cleaner box? I might be able to get one off a truck at an auto junk yard. I will definatley look into buying a 2nd catalytic converter for dual exhaust. Its just a matter of spending money for exhaust piping.

And i know the largest factor would be my differential. 2.8:1 standard (spins one wheels only). 8.3mpg town/highway combined with a 2.8 is bad enough, so i will leave that alone.

If i put a ricey exhaust tip on the caddy, i suppose i could get 300Hp out of a fart can, but i wont go there.


I am parking this car over the winter, so now is the time to fix the 8 track player. Any other things i will have to get started on ASAP.

Night Wolf
10-25-04, 11:01 PM
my '79 pulls like crazy thru 1st.... which ends around 53mph... then pulls nice in 2nd as well...

... the '79 actually accelerates faster up a steep grade better then my '93... either it is perceived by me, or the fact that it has alot of torque at a very low RPM...

once it hits 3rd around 85, it slows down... I know since i gutted the cat (drained the cataylist beads) that helped alot.... ntohing like going up a hill 40mph in 3rd, flooring it, secondaires opena nd a downshift to 1st... it literally thorws you back in the seat too...

for the time period, and the push for lower emmisions, and better fuell economey, I say the engine is not bad... if you replace the most restrictive parts of the engine (deisgned for better millage and low emmisions) which are the intkae system, cam and exhaust system... you will have a lot more performance form an otherwise stock enigne...

Night Wolf
10-25-04, 11:04 PM
also the standar rear end on these cars is 2.28... I think the limos got 3.08 or something similar...

... last time i check, I got about 12mpg around town and.... surprisingly 20mpg on the highway... I was only on the highway for about 30miles though, when I checked that... but still...

I'll be checking millage again.. I need to patch the hole int he bottom of my cat before I cruise in it... droning sound gives me a headache, and makes the car sound bad... (basically a big exhaust leak on top of the slight exhaust leak form the left exhaust manifold)

caddy4yaass
10-27-04, 08:22 PM
I just bought a 79 caddillac coupe, 425 in it. and i am looking to upgrade it [ engine power wise ].i have got the whole thing taken apart already all the way down to the camshaft. i would like to to make the engine run good street wise but still have some power to it. now i want to get a new carb intake, and exaust for sure,but were is a good place to get the parts from. thanks for any reply.

lux hauler
10-27-04, 08:39 PM
Summit and Jegs both sell the Edelbrock intake. The stock Quadra-Jet is good for overall power/throttle response and mileage. The exhaust will have to be custom.

abcdefg
10-30-04, 03:19 PM
Maybe 20 years from now i would like to turn this into a "drive it once a week to burn rubber for 2 blocks straight" car. Nice looking, quiet, smooth riding, fast...

My cadillac is acting weird. I floored it at a stop sign on a steep hill, and the right rear tire chirped. I was very dissapointed, i was being pushed back in my seat about the same as a 15hp riding mower. Before, at one time, i was revving my motor in drive with the brake on, next to one of my friends in a toyota. I didnt have any exhaust after the catalytic converter, so it had a bit of a rumble to it. I also liked how the whole car was rocking over to one side. I revved it at about 1 /2 throttle and the tires broke loose, so i floored it and let off the gas. I was smoking the right tire for a good 30 feet, before i let off the gas for a tight turn. In a round-a-bout, the right tire would do its stuff when i gave it too much throttle.

But i had to adjust the choke to rich, because the engine kept dieing before it was warmed up.

On ebay, i typed in 425 cadillac, and turned up with "Torque maximizer III" cams. I have no idea how special they are, and what good they would do me. The rpm range seems to be a little bit high for what i want, but everyone is looking for more hp options, we should just put a 350.

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&item=7931255557&category=33614&sspagename=WDVW

Once for 2000$ starting bid, there was a roots type blower that said it was made to use on a 500 cadillac engine, but i wont have a 2ft tall intake system sticking out of my hood.

Lets just say i had the intake ported larger (Not polished because its suppose to be rough) , lighter pistons, stronger crankshaft, good breathing heads and fuel injection, would that make a big difference (like 200hp difference?).

I need to write an angry letter to the cadillac motor division. Who ever thought of cramming the 425 in the back near the firewall so I cant get at anything. How am i supposed to remove the catalytic converter without ruining it, if i cant get a wrench on the bolts?

Maybe someone who knows what their doing should start an FAQ. Not many people know anything about the older cadillac engines. Theirs unhooking the exhaust, but after that things get vauge.

Many people around here suggest stupid stuff. "rebuild the engine"... That would leave me with what i have, a rebuilt 425 with under 1000 miles on it. K&N Air filter... I could use a riding mower air filter on the cadillac and it wouldnt know the difference. Putting a 350 in it? hahahaha, thats a good one!

TorqueInc
11-01-04, 02:36 AM
Kinda lost me there but..

There is alot you can do to improve the 425 besides just"rebuilding it"
One thing you can do is make the engine larger
A .040 overbore would be a start
Some head work including new valves,port work(nothing exotic),springs and a .020 cut off the face would do wonders.
a camshaft designed for the engine (torque cam 218-224@.050
Good sound machine work and a 472/500 intake manifold(modified)rebuilt Q-jet.
Headers if you have the skill to convert a set or buy some sandersons
You would have a good strong runner that would get decent mileage
I know of several good running 425's that have alot less that what i described done to them and are driven daily.
Nothing to it
a 472 or 500 would be better for power but you would be pissed at the pump as well.

Night Wolf
11-01-04, 04:36 PM
does a 472/500 really use that more gas then a 425?

since i gave up the idea of building up a nice 500 for my '79... I would like to keep the origanal engine, that way I can say "yeah, it has the origanal 425" and i am doing basic and simple mods so far... it seems like with a little wor, these can be opened up pretty nice....

how dificult is it to put a performance cam in the 425?

sethmartin
11-01-04, 10:19 PM
Headers if you have the skill to convert a set or buy some sandersons


Will the sanderson headers fit on the 425 in my 78 SDV?

7.0,hellyeah
11-05-04, 10:35 PM
Best parts ever for the 425, these people are really knowledgable: http://cad500parts.com/newpage1.htm Or go to cad500parts.com, click on complete motors, and in the same place click on the ultimate 425

caddycarlo
11-05-04, 11:10 PM
as far as I know there is no drop in header for your car .... I live in the same town as the cad co and know the guy that builds the headers they sell and he has not had a car in house to build a set for yet ..........

abcdefg
12-09-04, 11:05 PM
i still havent had my question answered:

By going with a 3x14" air cleaner box and filter, no exhaust (cut it off after it starts to bend into one peice) and a 500/472 intake manifold?

I know doing something that small can make a difference, just having the cat made the car really go better.

Dead Sled
05-07-05, 07:55 PM
since so many people have been asking about the 425 i figured I'd shove a big thumb tack through it and stab it into the top of the board

Night Wolf
05-07-05, 11:54 PM
i still havent had my question answered:

By going with a 3x14" air cleaner box and filter, no exhaust (cut it off after it starts to bend into one peice) and a 500/472 intake manifold?

I know doing something that small can make a difference, just having the cat made the car really go better.

What are you asking?

When I drained the catalyst beads from my cat. conv. it made a nice difference. the 14" open element Edelbrock air filter also helped a little.

I still have to install the modifed 472 intake manifold and the rebuilt carburator... that will fix my carburator problem and give me more power/fuel economy also....

But the 2.28 open rear end really has to go...

king of the road
05-08-05, 07:40 AM
ive thought to rip out the exhaust and the cat and center box,with a 2.5 pipe all the way to the back where ill fix ona muffler, i read somewhere on here as well that removing part of the intake manifold by machining it or whatever way possible will help it breath and to give my carb a overhaul, would fitting bigger jets bring about more bhp?, i know my fuel consumption would rise.

venom242
05-11-05, 08:47 PM
Richer jetting is definitely something to consider. I have heard that these motors were so emissions choked by the factory that they purposely jetted them lean, enough to melt pistons (rumor). If had known about that years ago, I might have rejetted my carb instead of doing my 500 swap.

After my carb was rebuilt by a local shop, my 425 ran like a dog. From that point on, I rebuilt all my own carbs. I highly recommend the Quadrajet book by Doug Roe if you want to know more about them.

Benlomand
05-11-05, 09:19 PM
I know a young kid that has a '79 deville, claims that the carb was rebuilt. Says it starts fine but wont run once he takes his foot off the gas. I'm not real keen on auto carbs but my SS on my Harley requires slight adjustment of the idle air screw on order to get it to run after repair. Single barrel though. Is the 4 barrel similar? and if not where can I get some info on how to proceed.:D

Night Wolf
05-11-05, 09:45 PM
Richer jetting is definitely something to consider. I have heard that these motors were so emissions choked by the factory that they purposely jetted them lean, enough to melt pistons (rumor). If had known about that years ago, I might have rejetted my carb instead of doing my 500 swap.

After my carb was rebuilt by a local shop, my 425 ran like a dog. From that point on, I rebuilt all my own carbs. I highly recommend the Quadrajet book by Doug Roe if you want to know more about them.

The carb on normal 425's are fine.. not leaned out or anything... if the car was equiped for cali. emmissions, then yes, it does have a lean-tuned carb along with other junk...

Night Wolf
05-11-05, 09:49 PM
Here is a question I have...

lets say I want to keep my origanal 425 in my '79... no 472/500 swaps...

Is the BlackBird kit from Cad Company a good choice?

for $4,000 you get all the stuff to build up your enigne to get 400hp and 500ft-lbs torque on premium pump gas.

So the question is... for $4,000 can you piece your own engine together and get more power... and still be reliable? and also... for $4,000 would it be betting to buy a 472/500 and build that up?

Just something I am thinking of... a 472/500 would be sweet... but it would require me buying another engine, then letting my 425 sit... when in fact I have an awesome running 90k origanal mile 425 sitting in the car as it is...

Of course there is machine shop work and whatnot, but I was looking at the kit, and that is looking pretty nice...

http://cad500parts.com/newpage1.htm

davesdeville
05-11-05, 10:36 PM
For $4000 it would probably be best to go for a 500..

Night Wolf
05-12-05, 11:34 PM
Yeah, it would probably be the best bet... and a 500... that would just be cool....

I would just hate to let my faithful 425 sit in the corner because of that... eh, I guess by that time it wont matter much, and I would have a great running 425 is I needed one, maybe a cool swap into a Jeep or something? :)

This time is long away though... but visions of my '79 pulling some low numbers at the drag strip and beating some unsuspecting sports cars, while surprising everyone is still in my head.... until then I can keep dreaming :)

Although I gotta say, given what was going on with the gas crisis at the time, the emmissions and all that other stuff, not to mention a 26 year old car that probably isn't as powerful as when it was new.... she really does move, especially from a roll of around 30mph, and this is with a carb that needs to be rebuilt. the 425 has never let me down :) just emptied my wallet at the pumps faster then I would like :)

davesdeville
05-13-05, 04:08 PM
Get a propane carb system, a late model 500 and swap the 76cc heads on it for 12.5:1... Propane's cheaper than gas and 12.5:1 is better than 8.5:1 or 10:1.

djcwardog
05-21-05, 02:29 PM
I am looking to buy a Deville this summer and the 77-79 cars have my interest, as do the 1980 cars. Both sets have smaller big block engines (425 and 368). If I decide to drop in a 500 (even a junkyard one at first), I'm told that everything bolts across as far as accessories, pulleys, etc. Of course the 1973 and 1975-6 cars also interest me! Tough to choose. 5000 pound car with mongo motor or 4000 pound car with smaller relative of it...

Anyway, for your question, I think I am with you on this. If it were me, and it could very well be this summer, I would want to tweak out the stock 425 (or 368 if I get a 1980 Coupe Deville, that year sure is good looking!) first for not alot of money just to see what it will do. Then if I decide it doesn't do enough, I can go ahead with the 500 option. So - to optimize beathing, first you need to at least port match your intake manifold. If you swap in a 472/500 one check its ports as well. You will not be creating extra work in doing this because you are going to have to remove the manifold anyway to do the one thing that is mandatory for you...

Pitch out that stock cam and put in something like the MTS 3 (for great torque and better mpg) or their MTS-5 or MTS-10, or even a just a stock spec 1973 cam, for better power over what you are getting now. Your stock smogger cam is retarded by design and not at all optimized for much of anything! A new cam with lifters is maybe $200. If you can use your stock rockers and valve springs then you are doing OK. Call MTS and ask them. Cad Co and Potter offer similar stuff as well... Comp Cams lists a few cams for these big block Caddys.

I would also recommend a true dual exhaust system custom bent at your local muffler shop. I like Dynomax Super Turbo mufflers but pick what you want.

Bottom line: short duration/high lift cam, port-matched intake, dual exhaust, and a proper carb setup to go with these mods and you will be at a point where you know whether or not the 425 will do it for you in the long run. If not, pull it and sell on ebay - someone else will want such a carefully prepped motor for their MPG king Caddy! You can then put in a 500.

Night Wolf
05-22-05, 12:40 AM
the cam.... I had a BIG discussion about that a little while back, I was very close to getting a #5 seires IIRC from MTS.

I do not want to remove the heads, and the process of replacing the springs, retainers and all the other good stuff was too much then I was willing to do. Plus all the cam will really do, for a near stock 425 atleast, is move the power band around.... which will make it rev higher, but also move the power up... which really isn't what I want with this car, especailly with the 2.28 gears, it bogs from a stop as it is, I don't need to make it worse by cutting more low-end power from the engine.

My 425 is all stock, and once it is warmed up and some of the carb issues are gone, it hauls... I am really happy with it's performance, I mean if you are doing 35mph and floor it, it downshifts into 1st and puts you in the seat until the shift to 2nd at 53mph, then keeps accelerating.... for what it is, the 425 does a great job at moving the car around. Once I do even a few mods (intake/carb etc...) I know it'll be running alot better too....

Night Wolf
05-22-05, 12:48 AM
Here are some videos and stuff of my stock 425, these were taken in the winter, I have since change some things on the car (interrior stuff etc...) I copied and paste this from another site, so I dunno if I may be talking about off-topic stuff, but it explains all the videos and I don't have to re-type it all :)


Once I fianlly get the miniDV camera, I am going to take some cool videos, these were taken by my digital camera in video mode (no sound)

plus the rear tires are completly bald now.... so I need to wait until i get new tires before I do much more of anything (some nice burn out videos will be coming soon though :)

0-65:

http://inoventionseast.com/1979%20DeVille/'790-65.wmv

highway (can't see the tach):

http://inoventionseast.com/1979%20DeVille/'79highway.wmv

highway with tach:

http://inoventionseast.com/1979%20DeVille/'79speedo.wmv

^I coudln't tell how fast i was going when I shifted into 3rd.... the speedo was burried :) and the GPS wasn't with me.... but I shifted at 4,000RPM, I could have held it out to 4,200 or so and got even more...... it is fun :)

This is why the tires are bald:

http://inoventionseast.com/1979%20DeVille/Caddymovie.wmv

^was for a contest that I didn't win :( (hence the short time)

Here is the sound form in the car, windows closed doing 0-85 or so. I just left it in drive, and it shifts into 3rd at 3,400RPM (when in drive) The ticking is the leaking left exhaust manifold, and the only reason why you hear the engine is because of the open element air filter, with that on, when the secondaires open, it sounds like it does int eh video. Witht he stock air clenaer, it is quiet. Also despite the high torque fo the big block, the car itself bogs from a stop, both due to the carburator needing to be rebuilt, and the gearing, you can kinda hear it bog a little in the sound clip. Besides the open element air filter and the cat. conv. that I drained the beads out of (still there though) the car is comeplty stock. Has a full tune up but that is it. With 90k miles, it runs great, but the enigne inside is kinda dirty, look in the valve covers it is sludgey, the new oil is really dirty within 3,000 miles or so.... but you really can't kill a big block Cadillac.... although you may go broke feeding it :)

http://inoventionseast.com/1979%20DeVille/VOICE010.MP3

All in all, not too bad for a 26 year old daily driver from the land of emmission-loaded, low compresson engines.... I am just holding off until I put a built up 472/500 into this car, get a nice 2.78 Posi w/ rear disc brakes from a similar year limo, and then we will be talking :)

djcwardog
05-22-05, 05:53 AM
Rick,

No need to pull heads to do what I'm talkng about. I agree (from reading the MTS web site) that the MTS 5 and MTS 10 cams move your power peak up the curve - and may not give you much extra peak power without head mods, etc... However, I believe that the MTS 3 cam will move your power peak to LOWER RPM's than stock. That is the idea behind that cam - gobs of low RPM torque at the expense of some high RPM power. If you can confirm that your stock valvetrain (springs, etc) will work with that cam, then it seems a great idea. Give MTS a call and let us know what they say. As you seem to agree, who cares about high RPM power with such low rear gears? Torque off the line is what this is all about. I like your videos! Does the tach on the column hide anything important? Were you able to find a nice one-piece strap with rubber sleeve under it or is it still the radiator hose clamp trick these days? I may do that if I get a similar car.

Night Wolf
05-22-05, 03:44 PM
the 3 series cam is not what I would want... it is a cam made for fuel efficentcy.... I really don't want the powerband LOWER then what is is stock, the engine has enough low end power, it is the top end where it lacks... so taking away from what it already dosn't have much of adds to that.... For my intentions with the 425 (mostly stock, some tuning etc...) the stock cam isn't a factor right now.... Maybe I can pull the thread that I was talking about swapping the cam.

The location of the tach does not block anything, not even the left blinker directional arrow, in fact it kinda matches the car, black background with white letters and a red/orange needle. having the redline at 4,000RPM is neat though... it is soo different then any other car I have been in, like my friends '01 Jetta 1.8T, or even my fathers '99 GP GTP, it goes thru the revs so quick, 100RPM means nothing.... but just look at the tach on the '79, the speedo moves faster then the tach! :) Not only that, but 100RPM on the 425 makes a world of a difference etc....

I have it on with double sided tape, which has now fallen off, so I will just put one of those big plastic pipe tie things on it and be done for now.

Also, the tach goes to 8,000RPM, so if I put it on 4cylinder mode, it doubles the real RPM, it is pretty cool to see it wind up to 8,000 or move so fast in this car :)

2 cool things I have noted though:

under WOT in drive, the 1-2 shift happens at 3,900RPM, and the 2-3 shift is 3,400RPM..... which is why when in drive it goes into 3rd around 85mph, but if you manually shift it and hold it out longer, it'll completly burry the speedo, and then go. I think I remember gearing the "redline" of the engine is around 4,200RPM.... I have shifted my 425 into 2nd at 4,600RPM (doing 65mph in first!) and it didn't like it too much.... by then the power is dropping way off though.

Also, the stock torque peak is at 2,000RPM, you would be very surprised to see that under normal acceleration form a stop, going from 40-60mph, or anything, when you hit the gas (not to the floor, but normally) the tach goes right to 2,000RPM, then sits there.... while the car is accelerating... the tach moves very slowly, but it just, for the most part sits there.... it is pretty cool how these engines move these cars with the gearing they have.....

abcdefg
05-30-05, 04:02 PM
To made an update:

My original catalytic converter finnaly plugged up (you cant blame it, it gave 29 years of reliable service).

I took my friends sawzall, and took care of that problem. I stared the engine up after that and mashed the gas in park a few times... Oh man, did it have a nice gurgly roar to it.

I installed about 10 feet of small fence post pipe (2" outer diameter) and rigged it up to the old exhaust hangers. The fence post pipe really toned down the bad-assness of the exhaust, but made it sound like a WWII propeller airplane with a 3spd auto. The exhaust noise under a heavy pull sounds nothing like a V8 untill the secondaries pop open.

As a side note to those wishing to remove the catalytic converter, check with your local state patroll... I was given the A-Ok on my car (because its older than dirt and we dont have emmssions testing). Emissions and exhaust noise violations can add up. Also, the gasoline and sulpher smell is pretty strong.

The acceleration from 0-50 really grabs me by my underwear now. I can leave long long strips of rubber with both tires in parking lots (the whole lenth of them doing a slight turn). Power braking is no sweat, flipping cookies also is easy.

I had my friends freaking out in the car (doing 55mph in a parking lot), they called it a piece of crap and said their toyotas were better... or so they thought :lildevil:.

I would be doing some real engine work.. But umm... Well, gas is TOO EXPENSIVE for 7mpg, so I just blew my cash on a diesel VW (50mpg).

Im low on cash (down to $1200, and unemployed). If I get some good income, im giving the caddy hell.

Btw, is the 425 engine a weak candidate for hot rodding? Im worried about the crankshaft, cooling, vavles, rods, pistons... Im looking for a lot more Torque under the 2000rpm range, 500Ft-lbs would be nice without forced induction or nitrous :).

abcdefg
05-30-05, 04:22 PM
I have shifted my 425 into 2nd at 4,600RPM (doing 65mph in first!) and it didn't like it too much.... by then the power is dropping way off though.

If I put mine in drive and stand on the gas at about 35-40, It will shove me in the seat, rev and roar up to 60mph, pause for a second, then go into 2nd gear. thats having it D and flooring it. Is this normal or is something adjusted wrong?

davesdeville
05-30-05, 07:14 PM
Btw, is the 425 engine a weak candidate for hot rodding? Im worried about the crankshaft, cooling, vavles, rods, pistons... Im looking for a lot more Torque under the 2000rpm range, 500Ft-lbs would be nice without forced induction or nitrous :).

It's a good engine, I'd say up to about 500hp. Once you hit those power levels (or if you're aiming for those power levels) it's time to think 500 or 472.

davesdeville
05-30-05, 07:16 PM
If I put mine in drive and stand on the gas at about 35-40, It will shove me in the seat, rev and roar up to 60mph, pause for a second, then go into 2nd gear. thats having it D and flooring it. Is this normal or is something adjusted wrong?

Sounds like the vacuum modulator in the tranny isn't hooked up to a vacuum source. On the back of the carb, either over or under (can't remember which) the brake booster vacuum line there should be another, smaller vacuum line which leads to the tranny. Make sure it's connected and if it is, pull it off and check to see if it might be leaking transmission fluid. If it's not connected, plug it in, if it leaks ATF you need a new vacuum modulator for it to ever work properly even though it's obviously still driveable.

Night Wolf
06-04-05, 11:41 PM
Here I am running the Caddy thru 1st gear... all stock, about to turn 90k.

The sound is from the 14" Edelbrock open element air filter :)

the carb needs to be rebuilt, the engine dosn't run as good as it should... and 2.28 gears suck. I just bought 4 new, kinda used tires, so I went out tonight doing my best to get some rubber.... but gosh! the car did not want to listen.... in this video the tires hardly spun from a stop, I wasn't able to do a brake stand (tried aobut 5 times) or even a power slide.... wasn't a very productive night :)

But i finally got my miniDV cam corder! still trying to figure out how to get the video ont he tape on the comp0uter, so these are form the little SD card... quality is bad, but there is sound :)

http://inoventionseast.com/1979%20DeVille/Caddy1stgear.AVI

Night Wolf
06-04-05, 11:47 PM
see.... she just didn't want to go along...

between the very high gears, and the 235 tires on it.... and the hesitation form an idle.... there isn't much overall low end power... it takes alot to get the 2.28 gears spinning... and stay spinning...

http://inoventionseast.com/1979%20DeVille/Caddy1-3drive.AVI

she was in drive, so it shifted into 3rd at 3,400RPM instead of 3,900RPm it shifts into 2nd....

Night Wolf
06-04-05, 11:52 PM
I go the tire to spin... but no nosie, just the enigne revving :) when I looked int he rear view there was a trail of smoke tho.....

http://inoventionseast.com/1979%20DeVille/quietspintire.AVI

Night Wolf
06-04-05, 11:55 PM
well, I think alot of it has to do with 2 factors:

1) to really get the car going sideways, I gotta throw it into the turn, but with all the foilage now, I gotta slow up to see if any one is there... not enough momentium to get is going...

2) I really need both hands on the wheel when trying to put the car sideways, it just helps me alot... and only haivng 1 hand ont he wheel and the other holding the camera is kinda hard in that respect :)

terrible one
06-05-05, 12:10 AM
Tape the camera to the right of the headrest or something

Night Wolf
06-05-05, 04:15 PM
Tape the camera to the right of the headrest or something

Yeah, I defintily need to get a way to mount the camra... I do not want to drill anything to the dash, and there is no where my tripod could go....

I'll have to see, maybe I could use the 3M velco stuff on it like i do my radar detector.... but then I would have to put more of that stuff on the dash since it is all the way at the front, near the windsheild for the radar detector... maybe a temp. way to mount it to the passenger side headrest?

TorqueInc
06-05-05, 07:16 PM
To pump up the power of a 425 do you really think you need a 4k kit to do it ?

I know you dont:sneaky:

Just a good rebuild will get you where you wanna be with some head work and thats the key.

another thing....do not ever replace a cam without replacing the stock springs at a minimum.
they have been there long enough and are always mush..TI

Night Wolf
06-05-05, 10:44 PM
well, I want to open up the 425 a little... what I really want to do is an all out performance build on a 472/500

For the 425, as far as performance goes, I want to install the modified 472 intake manidolf (once it gets modified) and the rebuilt carb (once it gets rebuilt) then get a nice free flowing dual exhaust on the car, which will stay on the car even with the 472/500, so that'll be a good investment.

Then I would like to find the rear end from a commercial chassis/factory towing package car... I want those 2.78 gears, Posi, and rear disc brakes just to show off :)

I know a cam and head work would do wonders.... but I really didn't want to get *that* involved with the 425....

Plus I'll be in FL in a couple months, with no cash to do anything with the car (in tech. school) so sooner or latter the car is going (back) to Florida.... so the 425 will power its way down there, I have always wanted a '77-'92 RWD Deville/Brougham to do a nice build up with, and I got one hell of a steal on the car a little over a month ago.... so now that I have the car, I can wait.... well, I really want to get a 472/500 just to "have" it, but now i am just waiting on funds.

Plus, I think between the carb/intake manifold and dual exhaust, the 425 will be running better already.... I know as it is right now, the carb is already causing (performance) issues...

77deville
06-08-05, 01:12 PM
I have similar issues on my 77 deville with stalling when cold, but it runs smooth when warm. The problem cropped up recently when I tuned it up, replacing the fuel filter, etc. Prior to that, I only had a little trouble starting after it sat for a week.

Did you find a solution to this stalling problem?

I haven't begun to tinker with mine yet (only got it 3 weeks ago) so it'd be nice to know what to try first.

Thanks in advance.

Night Wolf
06-11-05, 01:53 AM
simply put... rebuild the carburator...

besides the performance and fuel mileage benifit, on a 28 year old car, it would be a good thing to do anyway.... that should get rid of most your driveability issues too...

rdromano
07-02-05, 06:44 PM
you said to bolt on some headers.
Who makes headers for the 425? How abot ones that will fit teh FWD Eldo?

N0DIH
07-04-05, 03:20 PM
Anyone ever use a 500 cam or 472 cam in a 425? It would be a dirt cheap bigger cam.

The Ape Man
07-21-05, 01:50 AM
Anyone ever use a 500 cam or 472 cam in a 425? It would be a dirt cheap bigger cam.

As far as I can tell, the 425 and even the 1980 368 used the same camshaft as the 472/500. GM PN 1486583.

Fleetwood472
08-12-05, 01:29 PM
For you guys that have problems with your 425's stalling on you or hesitating when they are cold I used to have the same problem with my 78 Fleetwood. The carb was rebuilt the engine was fine and I changed the plugs wires, cap, and rotor and it still ran like that. Well I finally found the problem and its very simple to fix. What was happening was my advance weights in my distributer were slightly rusted so when they were cold they would sort of stick together and the car would run like shit for like 5 minutes when it was cold. To fix this you pull the cap off of the distributer then remove the 2 bolts that hold on the rotor and you can see the advance weights first I cleaned them off with WD40 then I oiled them and pulled outward and saw if they would spring back if they would spring back I would repeat the process till they did. Then I put everything back together and the car ran like a champ. Hope this post isnt too old and you guys see this. - Justin

N0DIH
08-13-05, 12:13 AM
HEI's had issues with the rotor burning through to the first thing they could arc to, the weights/springs. They took a hit. First sign that something is up is the rust color there. Keep the plugs/wires/cap and rotor in top shape, when the wires and plugs are weak, all the HV has to go somewhere, and the rotor takes the brunt of it. They should always be inspected closely.

WD-40 doesn't last too long, I would recommend some white lithium grease on the pins for the weights. They do wear, and will get oblong causing timing to get more erratic.

Glad you brought it up Justin, the HEI is an awesome distributor, and well maintained, will be a solid performer for almost any car, street or race!

Always inspect closely the cap and rotor wear. The rotor for burn through, and the cap for the HV arc to be stuck in one spot, that is a sign the mechanical or vacuum advance is not functioning properly. Always check the index of the cap too, if the HV arc is to one end of the cap contact, and never moves, (ECM cars are far more suceptable to this), and it is starting to arc off the end of the contact, the cap may need to be indexed. I did a post on how to in the Cad 4.9L/4.5L/4.1L section sometime back. It really improved the idle/low rpm drivability in my 85 Cutlass Olds 350 (was a 307) and the CCC computer system.

I have a "trick" good HEI mod (uses only factory GM parts) that really helps the starting and idle/off idle drivability in the HEI for high compression cars. If anyone is interested, let me know. It really works well with a non ECM HEI. Low compression cars it can help as well.

The Ape Man
08-13-05, 12:44 PM
When the distributor machanical advance gets stuck on these engines the culpret is not the weights and pivots. The binding occurs between the long shaft which is attached to the weight's hub whose other end goes all the way to the cam drive pinion and the outer hub on the top of the distributor who's inner diameter is only slightly larger than the shaft that it centers on. Hope this makes sense. The point is that the proper fix is to pull the distributor and clean everything then reassemble with lubricant that will keep working. I usually just take the fast route and bathe the hub with WD-40 while working it back and fourth. Most times this works. I then spray a little fast drying solvent like brake parts cleaner into the distributor to get rid of all the stuff. When taking the quick route it will be necessary to keep an eye on the thing as it will get stuck again sometime. Dunno if any other GM products ever had this problem. Maybe the Cad distributors were built with tighter tolerances and it resulted in binding.

abcdefg
08-26-05, 05:18 AM
Are you people trying to make me insane, with that familar sounding cad exhaust gurgle, and speedometer ripping from one side to the other video footage? Im still crusing around in a 1.6L diesel car http://cadillacforums.com/forums/images/smilies/crying.gif... If anyone cares to know, my 0-55 time on it was 20 seconds. I was going to do the 0-60, but it was taking waay to long so I just said screw it and stopped the watch. Also, I passed someone in it. Myes... 45hp to the ground, hit 65mph while doing it.

Im going into the airforce, and if it all works out for me, I should have some spending cash when I get back. Guess what im doing when I get back?

Latley I have been thinking of swapping in a cummings turbo diesel engine and trans into the '77 CDV. You know, save on gas and enjoy the 600Ft-Lbs of torque. But, I think id rather swap in a build up 500CI.

If the rest of you havent grabbed all of the 500CI engines out of the junkyard, then as soon as I can, I will certainly mash the go pedal on my diesel car up to spokane and rip out a 500CI or two, and bring them home on a trailer.

Btw, on ebay, there was a pre-hotrodded cad engine bored out to 514 inches for $6,000. Yeah, pricey, but it was shiney. They also had a blower to fit it for around $3,000. But, it was one of those real monstor sized blowers. That would really crap on my whole "keep it looking stock" agenda of mine.

These cadillac engines are wonderfull things. Hopefully, 4 years from now, gasoline wont be much over $3.00 per gallon.

eldoradoprime
08-27-05, 12:08 PM
on my 78 coupe to get some more snot out of it....i ripped out the resonators and put a straight pipe with a flowmaster , i ran a good air filter and the A/C never worked so we took the pump off the the top end and fiddled with the belt arrangement...seemed to work rather well from what i recall

Night Wolf
08-29-05, 03:31 AM
So if someone is going to swap the intake manifold...

lets just say they want to pull the heads and throw a cam, new lifters and springs in it...

while the heads are off, it would only make sens eto do some work on the heads.... right? then if so, what work?

If the object was to keep costs down, then would you even bother? yeah a valve job may help, but on an engine you don't plan on keeping that long? what about shave the heads slightly for boost in compresson? or is it the same idea?

Or if he heads were gonna get pulled, not even bother and just stick to the cam/lifters/springs etc... ?

BluEyes
08-29-05, 04:12 PM
If you're not going to keep the engine that long, I'd leave the heads alone. They do not have to come off to swap intakes, so just leave them be.
IF you were to do headwork though, I'd have a bowl blend done, install larger valves, shave the heads, and then re-work the rest of the runners slightly (in that order) Have a pro do the headwork though unless you know what you're doing - it is easy to lose power with badly done headwork! This all gets real expensive real fast though, so might be best to save the $$$ for a motor you plan to keep around awhile.
Also, with a new cam, keep in mind to not go too big on stock compression. You'll end up killing your lowend. I really wouldn't go a step or two above stock without adding significantly to the comression. Follow the cam-makers reccomendations for cam selection and you should be safe.

Night Wolf
08-29-05, 10:26 PM
yeah, I would have a shop do all the work.

It is just my "half way there, do it all" thinking... I will be installing a modifed 472 intake manifold and figured since I am there, see how much it is to do more... but I really think I'd be getting into more then I would like with the 425.

really, I am just trying to get a little more pep from the beast, the main purpose of the 425 though is to just be a reliable engine to move the car around until I drop a 500 in it... years from now... that also means that when the car comes to FL with me, the 425 will be powering it, I wouldn't second guess taking it to FL tomorrow, I know i'll do it, I just want to keep it that way and keep costs down also.

Night Wolf
09-16-05, 09:13 AM
In case anyone is wondering, the stock 425 in a stock 1979 Sedan DeVille with 91,000 miles is good for a 17.5s @78mph in the 1/4 mi. :)

Chrome
09-16-05, 12:51 PM
I have a "trick" good HEI mod (uses only factory GM parts) that really helps the starting and idle/off idle drivability in the HEI for high compression cars. If anyone is interested, let me know. It really works well with a non ECM HEI. Low compression cars it can help as well.

I haven't seen anybody ask yet, so what is this trick?

Thanks

m1gunr
10-04-05, 02:19 PM
Guys,
I'm helping my uncle get his 77 Eldorado (D'elegance Package w/425) up and running. He has determined the issue to the ECM needs replacing. His problem is locating the thing. Since I am new Cadillacs I have no idea where to start looking for the thing. I am 1/2 the state away from him and will visit mid October any help is greatly appreciated.

Bill
Driver Move Out, Gunner Take Over....

Night Wolf
11-01-05, 09:01 PM
well, I did the modified 472 intake manifold swap... but I am 1,500 miles from the car to see what kind of a difference it makes :) carb is awaiting to be rebuilt.

bigblockcaddy
12-29-05, 05:04 PM
i know a couple cheap improvements that work excellent for my 425 but everybody knows this..a brand new air filter,oil change,belts,oil filter,i know this works great for a fact cause i live in phoenix and i go up north quite a bit and one time a drove up north without no oil change,new airfilter,oil filter and i top'd my car off and when i got to my destination(1hour 45 min away) my caddy was already out off gas ...just on the way up their...then this christmas i went up north again got everything done and i still had 3/4 tank their and back...treat your car good and it will treat you good..thats for sure:helpless:

Night Wolf
02-24-06, 10:14 PM
Well... no more 425 for me.... damnit I miss that car so much now... never realize what ya have....until its gone...

Anyway, my list of, well, cheap power improvements to the 425...

- full tune up. This includes fluids changed, plugs, wires, cap and rotor, air filter, fuel filter, PCV valve etc....

- 14" open element air cleaner. Mine was made by Edelbrock, it looks really nice. Free flowing, and sounded sweet, especially when the secondaires opened :). It also greatly helped to clean the engine bay up.

- drain cat. conv. If your car still has the origanal cat... its plugged. Pry out the drain cap on the bottom and drain the beads... make sure they all come out... then take it to a shop that has those plugs... when I got an inspection on the car, the guy had a bunch of them laying around (old GM part) and charged me $5.... it was loud, but got annoying fast with the plug missing.

- rebuild carburator. The Qudra-Jet is a sweet carb, don't let anyone tell you otherwise... but obvisouly a ~30 year old carburater is going to have problems. Rebuild it, and if you know about carbs, or a shop does, then dump the emmisons settings from factory and go for a little performance, a stock Q-jet can be worked over to squeeze more out of it. Keep in mind this is an 800CFM beast that fits the engine perfectally, keep it. A good book for the Q-jet is Doug Roe - Rochester Carburators.

- find a 1968 472 intake manifold. This intake manifold, stock, flows alot better then the 425 intake. The '68 dosn't have EGR either, so the 425 now dumps EGR. While I don't mind EGR, with an old valve and lines, it is more of a problem then anything. Then, take the manifold to a machine shop and have them totally cut the center section under the carb out, so it is 1 big opening. You now have an intake manifold that flows 95%+ of the Edelbrock intake, for a whole lot cheaper. Sure it still weighs 45lbs, but it looks stock. This intake manifold will flow just as well as the Edelbrock until around 5,500RPM.... seeing as how these big blocks don't rev past 4,000RPM stock, you have to do alot to really get out of the effective range of it. It is also a low-riser intake, no more hood clearance problems. Perhaps the biggest thing is, you can still use the factory AC, not so with the Edelbrock. The A-4 from the 425 has a different mounting bracket, so to correctly mount the compressor, you need the 472 AC compressor bracket. Swap that over and she bolts right in. Revs smoother, sounds more healthy at WOT and noticeable power boost. The BB Cads are so cool, there is no coolant to mess with :).

Another non-engine related performance boost that really helped the car in handling and overall driving, was installing a factory rear sway bar. Mine was from a '79 Fleetwood, but I have been told 70's G-bodys use the same bar. Very nice mod.

The stock '79 DeVille with out 472 intake or rebuilt carb ran a 17.5@78mph. She was noticeably faster after words. I gotta say, the car was actually fast by the time I was done with these minor things. Floor it at 30 and she'll downshift into 1st, put you in the seat and you see the nose of the car jump up.

Other cheap things I had in mind was a shift kit for the trans... that would really help since the trans is calibrated for excessive slipping for smooth shifts.

Another thing that was going to be sweet, since the factory 2.28 gears don't offer much for performance, I was going to swap a cam in... not a hot cam, but a cam that brought the power band lower then stock... an RV cam. More low end torque at the expensive of high RPM HP. The neat thing is, the cams power band is idle-4,000RPM... well, it would shift at 3,900RPM going in to 2nd and 3,400RPM when going into 3rd, when in drive. It was perfect. The cam is the MTS #3, stock valve train is fine. It is also the gas saver cam and is very possible to get 20mpg+ on the open road... that was going to be the project. I wasn't ready to swap the rear end just yet, and so being stuck with the 2.28 gears, I was going to make a torque beast, a whole lot meaner.

Also, find the cross member from a Caprice 9C1, that way you can easily run true duals. True dual 2.25" exahust on a near stock 425 would be sweet, unleash a few ponies too, and with the MTS #3 cam, really open it up...

while on the exhaust note, the 425 manifolds are junk. Find a set of 472/500 manifolds, while not the best, they flow alot better, direct swap in for the 425, that and the true dual exhaust would be sweet.

There are all the basic plans I had for my '79... I had lots of plans. Hopefully this will help anyone else that just got a 425 and wants to bring the life back. Mileage dosn't effect the BB Cads much at all... meaning a 425/472/500 with 100k, if mainted thru its life, will show minimal wear and be ready for any plans you may have. Same goes for the Turbo 400.

- BTW from an appearance standpoint, something that REALLY helps the '77-'79 DeVille is to run a 2nd pin striping down from the fender and follow the body line that ends at the door. That right there is the missing link, without it, the car looked bland and missing something... I added that and DAMN those 2 pin stripes really set the car off like nothing else, it looked soo nice.

She will be missed....

http://inoventionseast.com/1979%20DeVille/79-2.JPG

burnrubber
02-27-06, 08:15 AM
One other performance mod, if you have your engine out for a refresh or rebuild is to have the block decked. As I understand it - at top dead center - the pistons are down in the holes a bit which could cause detonation. Besides preventing that - it should give a slight bump in compression which would be good for power.

davesdeville
02-28-06, 03:55 AM
Decking the block is usually done to get a good quench distance (piston to head dist.) Depending on the crushed thickness of your headgasket, you'll usually want around zero deck for a tight quench. Or you'd want to run the pistons way down in the hole, like .120, for a very loose quench. In between has a tendency to see detonation problems.

If you want a bit more compression have the heads milled. .040" which is about all I'd be comfortable doing, should get it to about 8.75:1 by calculations (which might be wrong since it's 1am and I should get some sleep.) Still would do well on regular gas, and might net you a dozen ponies or so.

bicentennialcadillac
04-23-07, 06:40 PM
Well, the '68 intake and '78 sway bar are lying in my office floor, and a crossmember from a '96 Impala SS is on the way.

I'm gonna put Night Wolf's plan to work.

N0DIH
04-23-07, 08:59 PM
Sorry, somehow I missed this question. I posted a writeup on it in the tech section. Basically it uses the EMR module to pull out 10 degrees timing by grounding a wire, unground it and it goes back to base timing again. So you can have an easy starting high compression engine and have a flatter timing curve and one that is ultimately more controllable and desirable.

It also helps you make a smogger distributor with limited mechanical advance a performance one, as the old performance distributors of yesteryear had lots of mech advance and little vacuum adv. You will likely need to watch your vacuum adv can usage, an adjustable is recommended. As the smogger ones are often 20-25 degrees, if not 30. So if you had a 25 degree initial advance, ground the wire and 15 degrees is your starting timing or nitrous timing, or turbo, etc, then when vacuum adv comes in, adding 25 to it would be too much and hitting upwards 50 degrees. I recommend not to exceed 45 degrees.

You can hook the terminal to a vacuum port with a switch, or a pressure port for boost, or even a line on a nitrous nozzle to automagically ground the distributor before pinging even starts to be an issue.

Really can be a handy dandy addition to a high compression engine or other performance uses.


I haven't seen anybody ask yet, so what is this trick?

Thanks

Night Wolf
05-03-07, 02:00 PM
Well, the '68 intake and '78 sway bar are lying in my office floor, and a crossmember from a '96 Impala SS is on the way.

I'm gonna put Night Wolf's plan to work.

:bouncy:

That is awesome... I still have my '68 intake manifold... I pulled it when the car was wrecked. You'll need to dump the EGR system though, normally I woudln't do that, but ah well.

'78 rear sway bar? you'll notice a big difference.... very good difference too, that was a really nice addition to my car.

And... cross member from the '96.... the double hump? I was looking for one of those... thats the only thing that kept me from getting a nice, new dual exhaust... the stock exhaust system is pretty bad.... some nice headers and dual 2.5" exhaust the whole way back would really wake it up too.

N0DIH
05-03-07, 10:44 PM
I have a 77-96 B/D Body rear bar that will be up for sale soon if anyone is looking. Should work in the 73-77 A/G body cars too. It is the large 9C1/F41/Impala SS/FE2 Fleetwood bar.

Yes, all 94-96 (all LT1) cars are double hump.

djcwardog
08-28-07, 05:08 PM
Anyway, for your question, I think I am with you on this. I would want to tweak out the stock 425 first for not alot of money just to see what it will do. Then if I decide it doesn't do enough, I can go ahead with the 500 option. So - to optimize beathing, first you need to at least port match your intake manifold. If you swap in a 472/500 one check its ports as well. You will not be creating extra work in doing this because you are going to have to remove the manifold anyway to do the one thing that is mandatory for you...

Pitch out that stock cam and put in something like the MTS 3 (for great torque and better mpg) or their MTS-5 or MTS-10, or even a just a stock spec 1973 cam, for better power over what you are getting now. Your stock smogger cam is retarded by design and not at all optimized for much of anything! A new cam with lifters is maybe $200. If you can use your stock rockers and valve springs then you are doing OK.

I would also recommend a true dual exhaust system custom bent at your local muffler shop. I like Dynomax Super Turbo mufflers but pick what you want.

Bottom line: short duration/high lift cam, port-matched intake, dual exhaust, and a proper carb setup to go with these mods and you will be at a point where you know whether or not the 425 will do it for you in the long run. If not, pull it and sell on ebay - someone else will want such a carefully prepped motor for their MPG king Caddy! You can then put in a 500.

UPDATE - I bought a 1977 CDV just a few weeks ago. I had true duals bent and installed - which required me to jet the stock Rochester carb up two sizes - from 72 mains to 74 main jets. I cleaned up the primary (seem to read as "62b" rods... and appear to be the newer style) and secondary metering rods and replaced both the choke pull-offs (primary and secondary). Already the car is faster than it was when I got it. I put on the offset MTS chrome 14" air cleaner to clear the stock a/c compressor. On hand is a pair of 500 exhaust manifolds and a 472/500 intake (with EGR - which I will not use). I also have the MTS-3 cam and lifters ready to go. I plan to remove the valve from inside the RHS exhaust manifiold and seal the holes so the gases flow better - no need for the heat riser/EFE warm-up here! Marty at MTS is sending me the 500 a/c brackets I need to go with the 500 intake. I'll post up results as I progress in this build-up. Maybe the 425 will do all I need until the block lets go. Of course, now I have all the parts needed to adapt a 500 short block (with the 425 heads and holes drilled in the 500 block for steam), or a 500 long block if I use the 500 heads... I know a guy who said his 77 CDV went 425,000 miles on the stock motor and ran fine when he sold it!

Benzilla
09-02-07, 04:07 PM
Post pictures of the '77 somewhere!

About the 425,000 mi Deville, that's nothing. The world record for the car going the most miles without an overhaul was held until very recently by a 1979 Sedan DeVille with just over 650,000 on the clock.

sleutelgek
12-10-07, 03:59 AM
Hello i have rebuild my 425 i have put a 472 intake on it from 1976
, but i have a carb thats belong too the intake can i used that or must to buy a original 425 carb, mayby the 472 carb its too big

thanks for your opinion.

the carb its a rochester quadrayet 17056230.

I have not 425 carb but it was earlyer a injected.

thanks sleutelgek from the netherlands (europe)

djcwardog
03-11-08, 05:20 PM
Post pictures of the '77 somewhere!

I just posted up a few pics on this site under Previous models - Deville. Not much to look at (yet) but it is a fun project.

djcwardog
03-11-08, 05:23 PM
must to buy a original 425 carb, mayby the 472 carb its too big...the carb its a rochester quadrayet 17056230.

Your 472 carb should work just fine. Be sure to use the correct ports and plug any ports not used so you don't have vacuum leaks. You may end up rejetting a bit but this is a good start.

BigPoppaD
03-17-08, 05:22 PM
I got a line on hopefully some 68 parts. How can I confirm that the intake and exhaust manifolds are truly the correct parts?

djcwardog
03-17-08, 05:37 PM
I got a line on hopefully some 68 parts. How can I confirm that the intake and exhaust manifolds are truly the correct parts?

I had this data in my spec lists - no guarantee that I have it right, but this manifold works on my car:

1605061 is a 472/500 stock cast iron with EGR – replaced 160955 stock 425 “negative rise” piece.

I also had this from a web poster:

‘68-mid’70 engines used the first generation heat operated choke, with an exhaust passage around the front of the carb. These intakes have a cast rectangular box-shaped choke well. Mid’70-’73 engines do not have the heat passage around the carb, and have a round choke well with what looks like a freeze plug in the bottom of it. (This describes mine) Many ‘68-’70 engines also had no EGR valve. All OEM 472/500 intakes are dual plane.

I surmise that I have a mid '70-'73 intake...

I don't have the parts numbers for the exhaust manifiolds. You want those that have a nice thick front runner (by this I mean the exhaust tube for #1 and #2 cylinder). The ones to avoid are the stock 425 pieces which have huge dimples cast right in on both the left and the right front runner.

deVille33
04-14-08, 01:30 AM
Wow! This post has a lot of history and a lot of info. There was someone selling crossmembers he manufactured for A bodies. The sugestion made here for the later C body looks good. Still available from GM?
ONe thing I thought of, You can change your cam's performance by adjusting cam timing by a couple degrees. You don't neccessarily have to give your money to a cam company for a mild timing change.

cadillac_al
04-19-08, 12:45 PM
Hey djcwardog, do you have any timeslips yet? Please let us know how the mods worked out.

steelybill
04-17-09, 07:48 AM
The after market cam guys like Comp Cams advise advancing the cam timing by like 4 degrees for low-end power, and retarding the timing by about 4 degrees for higher RPM power. There is no magic power boost in fooling with cam timing in general. Most folks install new cams "straight up", meaning the timing marks on the cam drive sprockets are lined up like an overhaul manual specifies, as opposed to setting it up with a degree wheel etc, for getting all available power.

BRICKS
10-11-09, 01:12 AM
:eyebrow::eyebrow::eyebrow::eyebrow:im gonna try out a few of these and see what happens from there. :eyebrow:

sleutelgek
10-16-09, 04:00 AM
Hello i buy a 2115 edelbrock intake for my 79" 425 cid coupe.
What gasket sal i take the edelbrock?
Or can i take a splasch pan a 425 or a 472?
I like splasch pan the intake are not too hot to.


thanks for your recomendations.

greeting Danny from holland (europe)

BRICKS
10-18-09, 04:45 PM
anyone have a price range for the intake? had someone tell me 200+ shipping on a 500 intake and 50+ shipping on the ac compressor bracket. a little much with shipping. picked up a caprice sway bar to switch over. just need a couple more goodies.

deVille33
06-08-10, 10:26 AM
The after market cam guys like Comp Cams advise advancing the cam timing by like 4 degrees for low-end power, and retarding the timing by about 4 degrees for higher RPM power. There is no magic power boost in fooling with cam timing in general. Most folks install new cams "straight up", meaning the timing marks on the cam drive sprockets are lined up like an overhaul manual specifies, as opposed to setting it up with a degree wheel etc, for getting all available power.

Your correct here. My statement, "changing performance", was wrong. Advancing or retarding the cam's degree of timing is a torque curve adjustment.
In the 1980s or sooner GM started changing the torque curve of the cams to enhance mileage, which made performance off the line anemic. Degreeing a cam is not magical, but you have to understand valve train dynamics and other aspects of your engine/drive train to maximize your performance / economy.

gornati
02-18-11, 07:16 AM
anything for the 425 fuel injected?
i have a 1978 EFI, but all i done if to put new plugs, change oil, fix the ECU, new air filter, new oil filter, new stainless steel headers and 2.5" exhaust with a flowmaster super 40 series...

anything else you guys would recommend?

DouglasJRizzo
02-18-11, 07:59 AM
anything for the 425 fuel injected?
i have a 1978 EFI, but all i done if to put new plugs, change oil, fix the ECU, new air filter, new oil filter, new stainless steel headers and 2.5" exhaust with a flowmaster super 40 series...

anything else you guys would recommend?

The EFI on 75 - 79 cars was primitive by todays standards. However, waking up a 425 EFI motor cant be too hard. People here have mentioned degree-ing in the cams and I think that would do a lot. One thing I've noticed about Cadillac camshaft profiles is that they are hyper mild.

Oh, one other thing. The EFI on the regular car line was different from the EFI on the Seville.