Been looking for a coupe for some time now. I got a 90 Brougham and want a coupe to do a 90 nose on. whell i dont want a 4.100.... ha...4100 LOL. But a 6.0... cast iron... NICE.

IN a 80 fleetwood brougham coupe.

Just wondering the pros and cons on it.

Thnaks guys!

con: its slow
pro: its not an HT4100!

it sort of goes on from there...

If you're gonna bother with a big block just go for the gusto, 472/500! :)

great engine, typical big block Cad fare.... just... smaller and less powerful.

Also, the aftermarket for it is bone dry.

But its better than the HT4100! never forget that... ever.

I wouldn't say there is no aftermarket for it... its a BB Cad... there are lots of BB Cad parts out.... not all are compatible with the 368, but some are.

The 368.... is a great daily driver, it'll go where you need to go with enough power to not feel like you are driving a sick dog. Its a Big block Cadillac, meaning it is nearly bullet proof and will keep running, for the era, its one of the best engines to have.

If you really want to start talking performance, then I would honestly swap it out, a 472 or 500..... and even a 425 is a direct bolt in, all 3 will net you more power out of the box, but you can easily go up from there.... its all bolt in.

Thats another thing I love about these cars, you can swap stuff!

can somebody please tell me why I would put a 500 where a 425 was, and not just build up the 425 since its like - the same engine?

Because more displacement = more power?

stock, the 500 had 180, so did the 425.

Thats another thing I love about these cars, you can swap stuff!

can somebody please tell me why I would put a 500 where a 425 was, and not just build up the 425 since its like - the same engine?

Yeah. The car rides better with more weight under the hood.

Thats another thing I love about these cars, you can swap stuff!

can somebody please tell me why I would put a 500 where a 425 was, and not just build up the 425 since its like - the same engine?

Well, you get more power out of the box, it has a slightly stronger crank shaft (honestly unless you are pushing 500+ hp, not a big deal) and you get to say 500CID.... the largest production V8 ever made in a car.

Otherwise, if you have a 425 already, its a solid start, it really is. 7.0L is nothing to laugh at.... more then a Frod 400 or Pontiac 400, slightly less then a Chevy 454 and the Dodge 440, nearly the same as the 426 Hemi and the 427..... There is alot that can be done to the 425 to wake it up, and for cheap, you can really boost the power alot.

Some areas where the 425 excels over the 472/500.... its lighter... both the block and the crank... if weight is an issue, this is a good thing. Also, she'll spin faster and at a higher RPM.... it has a huge bore and stroke, but not as massive as the 500.... shorter stroke = rev faster and higher.... not that either are something you really want in a BB Cad, but still. Plus, most the cars the 425 was in ('77-'79 DeVille) is alot lighter then the cars the 500 was in (~1975 DeVille) lighter car = faster.... so, the same work on the 425 in the organal car will make it faster..... although the 425 was stuck with 2.28 gears while the 472 and 500 got 2.73-3.08.....

Basically, if having a 500, just to have a 500 dosn't mean anything.... then go for the 425, its a great engine and you can really get some killer numbers from it. I wanted a 500 in my '79.....just to have a 500.... just so I woudln't have to ever hear "well, my Chevy 454 is bigger" and for my plans, the 425 would be getting a total rebuild anyway, so I may as well spend 300 bucks or so for a 500 core and build that..... but that 425 had some really nice potential.

Oh, keep in mind too... the 425 *IS* better on gas then the 500.... I know, I know... these things are gas guzzlers... but... really, a big block Cad is pretty fuel efficent for what it is.... my 425 was netting me 13mpg town and 17mpg highway.... not THAT bad considering.... if I did the minor performance mods for it, not only would she have more power, but it would most likely help fuel mileage since air flow in general would be better.

Some areas where the 425 excels over the 472/500.... its lighter... both the block and the crank... if weight is an issue, this is a good thing.

Do you have any data on that? How much lighter than a 472/500? Makes me think again about putting a 425 in my Camaro :D (didn't want the extra 60# of a 472 in the nose)

BTW: the 500 is only the largest POST-WAR production engine. Before WWII, there were MUCH larger engines than the 500. But, low compression (think 6 or 7:1) and side-valve technology (although some had overhead valves) made for pretty low torque & hp numbers.

I saw someone mentioned that a 500 and a 425 had the same HP. Don't forget that the 500 will make loads more torque. Another 75ci tends to do that.
Factory ratings from this era should also be taken with a grain of salt. Lots of other things going on with the emissions side of things that influenced the ratings. If you have a healthy 8.5:1 500ci motor with a freely flowing exhaust, you should honestly be getting somewhere around 300hp, 490lb-ft at the crank, stock. All at LOW rpm of course, shift before 4000rpm...

The only bad side to the 368 is really that it is overshadowed by the larger versions of the Cad big block. Honestly, 6L is alot of motor, even in a relatively heavy car. It's just that 7L+ is just that much more :)

Do you have any data on that? How much lighter than a 472/500? Makes me think again about putting a 425 in my Camaro :D (didn't want the extra 60# of a 472 in the nose)

BTW: the 500 is only the largest POST-WAR production engine. Before WWII, there were MUCH larger engines than the 500. But, low compression (think 6 or 7:1) and side-valve technology (although some had overhead valves) made for pretty low torque & hp numbers.

I saw someone mentioned that a 500 and a 425 had the same HP. Don't forget that the 500 will make loads more torque. Another 75ci tends to do that.
Factory ratings from this era should also be taken with a grain of salt. Lots of other things going on with the emissions side of things that influenced the ratings. If you have a healthy 8.5:1 500ci motor with a freely flowing exhaust, you should honestly be getting somewhere around 300hp, 490lb-ft at the crank, stock. All at LOW rpm of course, shift before 4000rpm...

The only bad side to the 368 is really that it is overshadowed by the larger versions of the Cad big block. Honestly, 6L is alot of motor, even in a relatively heavy car. It's just that 7L+ is just that much more :)

The weight difference... I don't want to say for sure, but its somewhere around 40lbs between the block and crank.... in the world of things, its not THAT much... but.... if you start with a 425 that weighs less then a 500 and add an Edelbrock intake manifold (22lbs instead of 45lbs) then you are now running a big block Cad for nearly the same weight as an SBC..... if your pockets are bottomless and you get aluninum heads, you have a massive enigne with very little weight.

Which pre-war production engines for cars are bigger then the 500? One of the largest that come to mind is the Cadillac V16 from the 30's.... but even then, that beast was 7.3L.... produced a smooth 165hp @ 3,000RPM and 320ft-lbs torque @ 1,200RPM IIRC.

Also, keep in mind the 425, while choked back with emmissions... isn't AS bad as the 472 and 500.... reason being... no AIR pump at all.... loose the origanal cat tho, thats a must (I drained the beads from mine)..... shes got EGR, but that is actually a good thing (and I ended up dumping EGR with the modified '68 472 intake manifold) and the carb is slightly lean (that was corrected with the performance rebuild) so that left the lack luster 8.2:1 compression as the only thing left, besides the smogger cam.... but because of that, I could run 87 and she'd never blink..... 87 will actually give it a little more power for the fact that it'll burn more easily.

The worst case 500 was making 180hp, the 425 makes 180hp...both these numbers do not reflect real world numbers, in general, the 500 was making more power, especially early versions of the 500 and the hi-po 472. But again, keep in mind, for what the 425 is, its making ecent power, and has some awesome potential too.... the 425 just dosn't get much credit because.... well... why get a 425 when you can have a 500, ya know? but she is a gem of an engine.... 1,400 miles in 36 hours without even flinching..... she would cruise at 75 all day and the only way I knew it was still running was the slight exhaust leak form the left manifold, the indication on the tach... and the fact that the car maintained its speed and the AC did its job.... and in the world of things, the 17mpg wasn't horrible either, cause if I was driving a gasoline pickup, thats what I'd be getting too.

a 500 is making around 300hp and 450ft-lbs torque.... even the smogger ones. I know I haven't updated it in ages, but take a look at the database thread (stickey at the stop) there are 2 articals of a BB Cad build up in there, and in the one, they throw a stock 500 on a dyno and they coudln't believe the numbers.

today, 6.0L is a big engine.... but the 368, wasn't making THAT much power not to say its a bad thing, but honestly, trying to make a 368 into a 1/4 mile beast woudln't be very sensable, it was at a bad era, cause the HT4100 was coming out which had what people wanted at the time..... The thing i like most about the 368, is the fact that the V8-6-4 stuff was slapped onto that thing.... I want a V8-6-4 368, and boost the power slightly... then wire up the solenoids manually (easy to do) to only have V8/V4 mode.... I think low-mid 20's would be possible for fuel mileage, and that'd be pretty sweet. if I had a 368, I would run it as is, if I had plans for hi-po, I'd step up to atleast the 425..... but thats not to say the 368 is left out.... AFAIK, she still has the claim of the smallest big block made :).

How much will draining the cat do for power? also, how did the modified '68 472 intake manifold help?

sorry for the dumb questions, but I'm just getting into engine modding.

So a bigger motor is a direct fit in?

How about the 4100's? Could you drop a differnt motor in one of them witho no problem?

How much will draining the cat do for power? also, how did the modified '68 472 intake manifold help?

sorry for the dumb questions, but I'm just getting into engine modding.

Draining the cat did ALOT. My exhuast had a rotten egg smell.... I pryed the plug off and drained all the beads... drove it around for a long time like that (she was loud) finally got a new plug in there... no more smelly exhaust, and you could feel more power.

the modified '68 472 intake manifold REALLY helped too.... it really flowed alot better and the power increase was abundent..... At the time of the accident, my 425 was still mostly stock, and I had alot more plans for it... but, for where it was, the thing hauled.... any speed it would put you in the seat... including 70mph.... downshift to 2nd at 70 and open the secondaires, and you could just feel the car accelerate fastly.... I gotta say she was a quick car for remaining mostly stock despite a few bolt on tricks.

So a bigger motor is a direct fit in?

How about the 4100's? Could you drop a differnt motor in one of them witho no problem?

the 368/425/472/500 are all the same family, (mostly) everything bolts right up.... a 500 would have been nearly a direct swap in my '79... swap the 425 pullies, oil pain and oil pump over and we were good to go.

the HT4100.... dosn't share much with any other engine at the time... so there is no direct swap for that.... its one of the more difficult engines to swap with for a few reasons too. But on the whole, it isn't all that bad and a 500, 425 or even a 350 is you wanted a SBC could be swapped in realitively easy.

Realitive is a loose term.... the space is there, and most the parts to get it to fit can be had for cheap.... then its just a matter of making it all work.

The 425 isn't going to be much cheaper to operate than a 500 if used in the same chassis. A good 500 driven conservatively will get pretty much the same fuel economy as a 425. If you pound it the story changes. The bottom line is vehicle weight, gearing and aerodynamics. You cannot obtain highway mileage with a '77-79 RWD Cadillac in excess of about 21 MPG without changing one or more of these. I've owned several cars over the years that started with 425s and landed up with 500s. Each rides better due to the additional weight of the 500. It's more than 40 Lbs difference. I have not weighed any but I'd guess it to be more like 100-125 Lbs difference. GM put their engines on a diet during the 425 years. An interesting swap would be a drivetrain from a 96 or so FWB into a 10% lighter HT-4100 powered RWD Fleetwood. That would probably reach the limits for fuel economy.
500 C.I. equipped RWD vehicles used a Cadillac rear axle that was different than corporate axles. The gear ratios were something like 2.93:1 or optional 3.15:1 .

For the largest pre-war engines, check here: http://en.wikipedia.org/wiki/List_of_automotive_superlatives
Go to the very bottom of the page. Largest is a 21.5L 4-cylinder!

Sadly, even the 500 has been surpassed recently. By 1%... 2003 Viper with 505ci.

anyways, back to the thread...

A 500ci motor will make more power and torque than a 425 given equal emissions equipment and exhaust. 75ci of extra fuel and air being pulled in each intake stroke will make a difference. It's the same reason that people stroke their motors to go faster. Just because the factory only had 180hp out of a hugely de-tuned 500ci motor does not show the motors potential. By the same token, you could swap in any number of V6's made in the last 20 years that also make 180hp and then build that up, but it wouldn't get you the goal you are after. ;)

I might just have to snag a 425 out of the junkyard and weigh it... I actually re-checked my data and found that the 472/500 motors are more than 60# heavier than a 350 SBC, but if a 425 comes in light enough. hmmmm...

I guess the direction of this thread shows the fate of the 368. Red-headed stepchild of the bunch I suppose. Only a product of the fuel economy requirements that started in the late '70's and probably never would have existed otherwise. Cadillac probably could have kept the 425 motor up with emissions regs for longer with better EFI systems, but that combined with fuel economy requirements forced Cadillac to make do with shrinking down their big block untill a new engine family could be designed.

Logically, I suppose one would put in a 400ci Chevy smallblock before a 368. The 400 motor weighs less, costs less, has tremendous aftermarket support, etc... But, that wouldn't be a Caddy motor then, and that's the whole point here. I'm pretty sure you already have a bellybutton ;) haha.
I suppose if you just can't find anything larger than a 368 to replace the 4100, then go for it. Coming from the 4100, it will probably feel like a sports car anyways. 1.9L more - it's like you've got an extra engine under the hood! Of course, be prepared to long for even more power and the urge to swap in a larger Big Cad when you find one ;)

For the largest pre-war engines, check here: http://en.wikipedia.org/wiki/List_of...e_superlatives
Go to the very bottom of the page. Largest is a 21.5L 4-cylinder!

Sadly, even the 500 has been surpassed recently. By 1%... 2003 Viper with 505ci.


Nope!

I said "largest production V8 used in a car" and the 500 still holds that fame. None of those pre-war engines mentioned were production, they were all low-quantity hand built jobbers.... same witht he Viper... that is not a production car, or engine.... the 500 was.

Shes still got the claim to fame :).

The internet can be a dicey place to get correct information. The 472/500 can be found in several different places weighing anywhere from 625# to 720#. Same charts show the sBC at 575#.
Here's one:

Scroll down when you get there.

http://en.wikipedia.org/wiki/Cadillac_V8_engine#425

The thing that worries me is they say that the 472 was heavier than the late 429. Anyone weigh a late 429???

429 was more heavy then the 472.... thats one of the many "advancements" they didhad with the "modern" engine at the time..... dunno why it would say that...

The 500 is the largest **V8** ever used in a regular production car. Lets not get into double digit cylinders and industrial or crate engines. The 500 was the largest V8 ever put into a passenger car that roled down an assembly line.

As for direct swaps with the HT4100 look to Oldsmobile. The Olds 350 and 403 are pretty direct swaps. An Olds 455 can be made to fit, but it has a higher deck height than the 350 and 403 so you'll need to do some modifications. You just need the motor mounts, brackets, etc. from a Diesel Caddy (The GM Diesel of the early 80s was based on the Olds 350).

this might be a little off topic but wouldn't a high compression 472 get better fuel mileage than a low comp 425? Just wondering because I recently replaced the 425 in my 77SDV for a 1969 472 with 950 heads and a 6500 block.

Wow this thread grew a TON in the last 30 hours since I was last on here!

Anyways, will a '77-'79 Sedan deVille run a quicker 1/4 mile than a '75-'76 deVille? I think so. I think it's like 17.5 or so for the 425 and like 18.1 for the 500.

Wow this thread grew a TON in the last 30 hours since I was last on here!

Anyways, will a '77-'79 Sedan deVille run a quicker 1/4 mile than a '75-'76 deVille? I think so. I think it's like 17.5 or so for the 425 and like 18.1 for the 500.

yes.

Having had a 78 Fleetwood Brougham and 75 Deville, both stock, they're both equally slow. I'd dropped the beads out of the cat on the 78 and after that it was noticibly faster.

The '76 will win. It has a much better gear ratio for 1/4 mile times.

Anyways, will a '77-'79 Sedan deVille run a quicker 1/4 mile than a '75-'76 deVille? I think so. I think it's like 17.5 or so for the 425 and like 18.1 for the 500.

From: http://www.100megsfree4.com/cadillac/cad1970/cad77.htm (hope they don't screw up this link like cadillacowners.com did...) <- edit: yeah, they censored me. WTF? #$%^ pinkos...

(1977 Cadillacs were) "an average of 950 pounds lighter than their massive predecessors"...

The rule of thumb in drag racing is that for every 100# you drop, you should go 0.1 second faster. So, they drop 950# but at the same time lose 75ci and only go 0.6 seconds faster through the quarter, not 0.95 sec.

Still too many variables to compare the two and draw many useful conclusions - you can't compare different engines in different chassis and draw any conclusions except that a stock '77 Caddy was faster than a stock '76 Caddy.

Let's run a stock '77 against another '77 with a stock '76 500ci motor swapped in before drawing any conclusions. I know where I'm putting my money... But, hey, maybe we're wrong about this whole displacement thing and all the stroker kits and big engine swaps and etc out there are just a scam... :)

My '79, all stock with 88k or so ran a 17.5s @ 78mph.... this dosn't reflect when new, this relfects as she was at the time. After that I did some minor performance mods which really opened it up nicely.

I still think the '77-'79 will be faster.... the extra displacement of the 500 isn't enough to warrant the extra 1,000lbs.... power output was similar.... keep in mind, the 500 was bogged down with more emmissions then the 425.... 425 never had an AIR pump etc...

the 500 has the gears, but the 425 has the weight on its side....

Lets see here...the 1976 4BBL 500 was 190hp & 360 lb/ft, but that was probably underrated. The 1976 Fleetwood Brougham was 5213 lbs dry.

In a 1975 issue of Motor Trend, they tested a '75 Eldorado Coupe with the 4BBL 500 and got a 0-60 of 10.9, and a 1/4 mile of 17.60@ 78.1 MPH, so maybe the 425 isn't that much quicker

The 1977-79 425 4BBL was 180hp and 325 lb/ft. I'm not sure how underrated that is, if at all. The 1979 Fleetwood Brougham was 4250 lbs dry.

I wonder what a '77-78 Eldo is capable of...

noooooooo don't start the numbers thing again......

I am the Rain Man! :D ;)

A.I.R. pumps used very little horsepower. Some 425s did have them.
Dunno about Fleetwood. '76 CDV weighed in at 5075 Lbs at raceway park right after I ran 16.4. Car was all original except for a gutted cat. I raced a guy with another '76 CDV on the 3rd run. His ran 16.01 with a posi limo rear, cool can and some ignition work.
Gears can make quite a difference.
A 500 in the '77 makes for a nicely powered vehicle.
I put one together in October of 1987.
Got another in October '88.
Put the entire stem to stern drivetrain from the first '77 (including the 500) into a 1983 CDV back in 1993. Best car I ever had.

A 1976 Coupe deVille that runs a 16.4 is mindblowingly awesome! It could almost keep up with a 4.9 powered car despite the additional 1600 lbs of weight.

Greetings,
It might be a little late, but I wanted to comment on the Cadillac 368 engine. I had a 1980 Seville with this engine. It was the smoothest, quietest engine I have ever experienced. I have a 95 LT-1 Fleetwood and I have had a 1971 472 sedan deville. Both of those are much more powerful, the LT-1 giving me the best performance and mileage, but you could have balanced champagne glasses on the Seville hood with that 368. At full throttle, it was a whisper. The power was good enough to move the Seville pretty fast around town, with more flooring necessary to maintain highway speeds (no overdrive in 80). It is much faster than the 4100 and faster than the Fullsize 77 Grand Prix that I had with a 301. The only con is the fact that electronics, like the Throttle Position Sensor (TPS) is unique to 1980 and is not produced anymore. A NOS one is $250 and very rare. On another note, 1980 is a horrible paint year. GM used dispersion lacquer and it gets massive alligator cracks if you attempt to paint over it. The whole car has to be stripped to respray any part of it.

Jed95fwb I bought a 1980 cdv last fall,24000 miles on it,368,this motor suits me fine,everything is comparable, I've never driven any other big blocks, I was interested in your seville having no over drive,I havent checked everything out yet on my car,do you know if cdv had o/d?. the paint on my car is in great shape,most people think it's had a new paint job,wonder if seville's were painted in a dfferent factory?. Ken

Cadillacs did not get overdrive until the 4.1L V8 was introduced in '82.

Kinda ironic,with an advancement like overdrive coupled with the 4.1.

Kinda ironic,with an advancement like overdrive coupled with the 4.1.

Not really.... The HT4100 in itself was a very advanced engine for the time, digital fuel injection and on board diagnostics among others. HT stands for High Technology. It was underpowered in the full size cars, and later in life proved to not be very reliable.... but at the time, with the gas crisis on hand and everything going on, it was what they needed. An HT4100 w/ OD will get about 24mpg on the highway....in the early 80's, that was amazing... compare to just a few years before, you had my '79 DeVille w/ 425 and no OD getting 17mpg tops.

It's like if Cadillac somehow made a '92 deVille that could get 32MPG on the highway, not the 25 that mine does. Amazing!!

Greetings,
It might be a little late, but I wanted to comment on the Cadillac 368 engine. I had a 1980 Seville with this engine. It was the smoothest, quietest engine I have ever experienced. I have a 95 LT-1 Fleetwood and I have had a 1971 472 sedan deville. Both of those are much more powerful, the LT-1 giving me the best performance and mileage, but you could have balanced champagne glasses on the Seville hood with that 368. At full throttle, it was a whisper. The power was good enough to move the Seville pretty fast around town, with more flooring necessary to maintain highway speeds (no overdrive in 80). It is much faster than the 4100 and faster than the Fullsize 77 Grand Prix that I had with a 301. The only con is the fact that electronics, like the Throttle Position Sensor (TPS) is unique to 1980 and is not produced anymore. A NOS one is $250 and very rare. On another note, 1980 is a horrible paint year. GM used dispersion lacquer and it gets massive alligator cracks if you attempt to paint over it. The whole car has to be stripped to respray any part of it.


http://www.partsamerica.com/ProductDetail.aspx?mfrcode=SMP&mfrpartnumber=TH1&parttype=280&ptset=A