: New muffler makes my 425 into a rocket!



tripleyellow78cad
04-27-05, 10:14 PM
Man I had a new muffler put on my 78 coupe (the old one was a piece of cR@P)
man i hate mid@s, only 5 years and 25k and it @##$'$ up!
anyway tis car now revvs up alot faster the 4bbl open faster and i can beat some of those ricers off the line quicker now
man what a fun car to drive:lildevil: :burn: :rant2:

N0DIH
04-27-05, 10:22 PM
With the less backpressure it will likely lean out the fuel mixture a bit, you may need to tweak the rods or jets depending on if it affected much. Leaner is better for fuel economy, but often raises HC levels, but drops CO levels. With the combustion chamber temps higher, NOx levels may also increase some, but EGR should keep that in check.

Glad to hear it! Now, add 2 and make it duals!!

Can ou add in a crossmember from a 94-96 FWB and get duals down each side?

tripleyellow78cad
04-27-05, 10:51 PM
With the less backpressure it will likely lean out the fuel mixture a bit, you may need to tweak the rods or jets depending on if it affected much. Leaner is better for fuel economy, but often raises HC levels, but drops CO levels. With the combustion chamber temps higher, NOx levels may also increase some, but EGR should keep that in check.

Glad to hear it! Now, add 2 and make it duals!!

Can ou add in a crossmember from a 94-96 FWB and get duals down each side?

I would love to add duals but i live out in ca
and the car must pass smog inspection every 2yrs and they put your
BXXX's in a vice if you change anything:banghead:
my best bet would be to upgrade to 3inch but $$$$ is a liyyle tight right know
with gas prices being $2.70 a gallon:banghead: for 87 octane

thanks for the relpy

lee

davesdeville
04-28-05, 12:56 AM
Crap, balls.

Too bad you have emissions, those first generation cats really rob power. Maybe you could get a higher flow later model cat.

tripleyellow78cad
04-28-05, 01:39 AM
Crap, balls.

Too bad you have emissions, those first generation cats really rob power. Maybe you could get a higher flow later model cat.


it dosent have the old cat, newer midas one:banghead:

davesdeville
04-28-05, 02:04 AM
I don't know why you're banging your head about that, anything's better than a 27 year old cat..

tripleyellow78cad
04-28-05, 03:59 AM
I don't know why you're banging your head about that, anything's better than a 27 year old cat..

I just dislike my local midas shop, they burned me a few years ago, the original owner of this cad went to midas I never would have though.
Any simple and cheap ideas how to make this 425 haul @$$ even more?

Lee

N0DIH
04-28-05, 06:43 PM
ok, where are the sound files? We want to hear it!!

davesdeville
04-28-05, 06:59 PM
You could get away with a 100-125 shot for under $400...

tripleyellow78cad
04-28-05, 07:36 PM
nitro would be cool too many mods plus the $$$
i was thinking maybe a flamethrower coil and dist cap,plugs and wires, i currently use
acdelco rapidfire plugs and the work quite well
lee

ShadowLvr400
04-28-05, 08:56 PM
Basic mods to perk up a 425 are the same classic ones you'll always hear. Go 4 bbl if it doesn't already, headers, exhaust, msd ignition is useful, then some head work and cam work. Other things include a rear end swap for a better gear ratio, and posi if it doesn't have it already.

tripleyellow78cad
04-28-05, 09:02 PM
I would love to get my hands on a posi, this damn thing has a 2.28 open rear ,
does andbody know if a 78 fleetwood rear with factory drear disc brakes fit my 78 coupe deville?

ShadowLvr400
04-28-05, 09:24 PM
Probably, but a simpler way, is go under the car, and see what rear end is there. Grab a ruler, see the diameter, and count the bolts. I wouldn't doubt it's a GM 10 bolt 7 1/2 or so. Possibly a GM 12 bolt. Ruler and counting should give an idea.

As a note, you could probably have your original rear end rebuilt with the gears you want, and have disc brakes attached to the rear axle. Not that difficult. Also, could just measure it, and have a tank built. Shove a rear end in, with some beefed up axles and disc brakes, some custom mounts abd be off with that. The Ford 9" fits in a ton of cars, your 78 shouldn't be hard to shove one in.

tripleyellow78cad
04-28-05, 09:44 PM
i would really like to use the fleetwood rear if at all possible
lee

davesdeville
04-29-05, 02:38 AM
If you have emissions to deal with, a dual exhaust setup might not be possible. Without duals it's kinda pointless to get headers. All the big blocks came with Quadrajets so not much improvement there. I wouldn't spend my money on ignition - the engine's not gonna see over 4500rpm and HEI is fine at that level. Get something better than that 2.28 open rear. The fleetwood rear setup should fit and rear discs are nice, but my 78 Fleetwood was still a 2.28 open diff.

Nitrous on the other hand is cheap and easy. All you need to do is put a bottle in the trunk, a plate under the carb, and switches to make it go. At that low of a hit I think the stock mechanical fuel pump should do OK, if not an aftermarket Olds mechanical pump will work.

ShadowLvr400
04-29-05, 02:35 PM
TripleYellow, a Fleetwood one won't be as strong as you'd really need anyways. It'll hold the stock power, and a little more, but for the same price, you could shove a performance one in, with whatever gears you want, and have more durability, and probably awarranty.

JAKE91
04-29-05, 05:03 PM
TRIPLE, GLAD TO HEAR IT. :thumbsup:

MY '79 CDV WAS SAME COLORS AS YOURS. I LOVED THAT CAR. IT DID NOT HANDLE AS WELL AS MY FWB BUT THE RIDE WAS SMOOTHER. :)

tripleyellow78cad
04-30-05, 05:07 AM
TRIPLE, GLAD TO HEAR IT. :thumbsup:

MY '79 CDV WAS SAME COLORS AS YOURS. I LOVED THAT CAR. IT DID NOT HANDLE AS WELL AS MY FWB BUT THE RIDE WAS SMOOTHER. :)

Oh h#ll yeah, very smooth ride , loves to float! while doing 75mph:eek: :D :thumbsup:

gotta love the cool triple yellow cads, and you gotta love leather:)
I bet you get better fuel mileage , city 8-9,if i'm lucky, hwy10-,15 if i/m driving down hill with an 80mph wind blowing my homemade sails:eek: :histeric: and no a/c on

N0DIH
04-30-05, 03:51 PM
Car 12 bolts died in 1973. You have 1 of 2, 7.5 or 8.5in 10 bolt.

In all of my GM FSM's there were not a single 8.5" with ratio's less than 2.41.

Hints for rear ends. Diesels almost all got 2.93's and 8.5". All HT4100 RWD cars got 3.42's and a 7.5", and high alt cars got 3.73's and 7.5". Low cost performance upgrades.

You should be able to bolt on rear disc from any of the factory 8.5" cars on a 8.5". To my knowledge, no 7.5" ever got rear disc in a B/D car. But the 8.5"s did, it was an option in the 77-80 cars, and also on the 75-77 Eldo's, these parts all bolt on to a 8.5" 10 bolt. Also the 94-96 9C1/Impala SS cars rear disc also should bolt on with no issues.






Probably, but a simpler way, is go under the car, and see what rear end is there. Grab a ruler, see the diameter, and count the bolts. I wouldn't doubt it's a GM 10 bolt 7 1/2 or so. Possibly a GM 12 bolt. Ruler and counting should give an idea.

As a note, you could probably have your original rear end rebuilt with the gears you want, and have disc brakes attached to the rear axle. Not that difficult. Also, could just measure it, and have a tank built. Shove a rear end in, with some beefed up axles and disc brakes, some custom mounts abd be off with that. The Ford 9" fits in a ton of cars, your 78 shouldn't be hard to shove one in.

SolidGoldsteen
04-30-05, 04:05 PM
What about some specifics here guys...? I just bought an 84 Sedan Deville yesterday, not even 24 hours ago...

Right-Lock any good? Quaffe?

Flowmasters are all good right? Or Borla (model #what?)

Must get this thing on a lift and see which cat it has. The engine/transmission have about 40k on rebuild, so everythings been replaced...