stxbuck

Hi guys, new member here. Just wanted to say I have learned a great deal from many of you guys here. But I need some help. I have recently purchased a 79 T/A with a 403 olds. I want to keep the car as stock as possible. But with the limited HP I wanted to give my old olds 403 some power. Nothing fancy, streetcar with a little juice. I was thinking about changing the steel intake manifold to an aluminum one, maybe some headers, a good exhaust system, a mild cam. What do you guys think? I already searched the forums and threads but all I read on is some major mods for high HP. ANy help is appreciated or if anyone can point me in the right direction. Thanks.

70W-32

What is your re axle ratio. Most T/As had mid to high 2.xx If you change to a 3.23 to 3.42 ratio the car will be completely different without you having to tear into the engine,

Keep in mind that a intake manifold change may affect how the shaker fits.

stxbuck

The sheet reads GU1 241 Ratio Axl
and G80 posi axle

Fun71

Ugh, I thought my car was bad with a 2.56 rear, but 2.41 must really suck.

As said, swap that to something in the mid-3 range and it will feel as if you have a lot more horsepower. I did that in my old 70 Supreme, going form 2.56 to 3.08 felt like I added 50 hp, then again swapping from 3.08 to 3.55 felt like another power increase. Do a gear swap and you won't be disappointed. The rear gears will already be there to complement any engine mods you may do in the future.

fleming442

Rear gears for sure. You'll lose some top end, but be realistic; how often do you do that, anyway?

Engine wise, intake and a manifold back 2.5" dual exhaust will be more than you need with bolt on mods. Keep in mind that it's only 7.9:1 compression, so most things like headers and a cam are futile. Do some thin Cometic head gaskets before all that..

Your local emissions regulations make a big factor to consider.

matt69olds

Put 3.73 gears in the rear end, swap in a 200R4. If that’s not enough, a little exhaust work would be a improvement

olds 307 and 403

We have a winner. The stock 4A heads are terrible on the exhaust side. Early 350 heads will raise compression a point, you need a A4 or Performer on a Trans Am to work with the shaker. Then a cam swap on top of the rest will make it a fun car.

BackInTheGame

You guys are making me miss my '79 T/A..

Koda

Both points are excellent; that engine has to have the turd fixed before you polish it, which is that it's late 70s emissions style setup, so, compression.

GEARMAN69

3.08's would be a awesome upgrade and still driveable on highway. Headers for sure. a set of 68-72 350 heads 5, 6 , 7 , 7a with bigger valves like 2.07/1.62 combo (open up heads bolt holes to match 403 if using the early heads) , a mild cam ... honestly a generic @ 050 rated 214/224 112 is plenty and work in the rpm range this head swap on stock dish pistons gets you up to 9.5:1 ish ad needs 93 octane.. A simple regular Edelbrock Performer .. If you don't change heads go with a different cam for the low CR with a tighter 108 or 110 lsa just regardless intake side at least 210 @050 but not more than say 220 degrees

Lost of opinions and options here. on a stone stock engine I wouldnt go all the way to 3.42 gears from 2.41 , 3.23 overall best IMO max

One of the guys I race with is a original owner of a 403 car he bought new and that original engine with some marine cam swap with 3.23's but still low compression 7.9 ended up in the low 13's in 1/4 on slicks, now its 12s with a Pontiac engine but still very good results for low CR 403

stxbuck

in my research I've read about the horrible compression. But where I am parts are non existent and there are hardly any master mechanics that know how to deal with the older engines.

fleming442

I've read and reread this several times. You don't have to be a "master" mechanic. You're dealing with basic engine principles: suck, squeeze, bang, blow.
Or, are you saying that the mechanics around you don't know anything beyond a code reader and Google?

olds 307 and 403

Wait till the new small chamber Edelbrock heads come out. Dual exhaust, maybe headers and a cam swap will be all you need otherwise. Mark is trying to convince them to do them so a regular Performer intake can be used without welding.

Fun71

I agree, you don’t need a master mechanic to swap heads or install a camshaft. I did that stuff when I was in high school. Just remove parts then reverse the process to install the new ones.

cutlassefi

^^^^^^ plus you have less than 8.0:1 compression in stock form so a cam change would be like putting lipstick on a pig, waste of time and money.
Thanks.

CANADIANOLDS

To wake it up a gear swap is the easiest and least expensive. gears for the 8.5” are cheap new or used. Go 3:08 minimum

A cam swap is also a good idea. You need a low rpm TQ type cam with short advertised duration with good lift. You have a few choices that will work with the stock heads as is.

best ones are;
Comp XE250H
Comp 250H
Lunati 60800LK

add headers if want but these will work well with stock exhaust manifolds

always rejet the carb..those are notoriously lean

olds 307 and 403

The idle circuits are probably the main issue on these late 70's carbs, especially if the compression and cam are increased and headers installed. Cliff has a nice custom 44 primary rod for these. Tune with a wideband to get it bang on.