I have an 87 GTA w/ 305 TPI - I'm in Australia and it's RHD converted which means no off the shelf headers will fit and it's a custom job. I've been quoted around $3000 for this (just the headers).

Current mods are basically the usual tune up and K&N / 3" intake piping. Given that I'm running stock internals, from what I've read here I might not pick up that much gain from headers and my $$ might be better spent on other mods that will give me more bang for the buck. I'll still do the exhaust from the manifolds back, probably 3" with hi-flow cat, so that is money that will be getting spent regardless.

Any opinions? I'm thinking cam might be more beneficial? What other alternatives?

My preference is for DIY but I'm not sure I'd do a cam or heads myself. Intake manifold gaskets was adventurous enough for me. So some "lesser" suggestions are also welcome!

Thanks,
Stu

 

The tech section on this site might offer you some easy and fairly free mods tips. Otherwise, if you're not into wrenching on the internals consider all other bolt on alternatives. Not sure what kind of rear end gears your car has but, complete rear end swaps are not that difficult and a new set of gears might add some pep. Or, a mild bolt on spray kit or even a supercharger, are all bolt on items that most folks can handle.

Good luck

 

I'm guessing RHD is right hand drive... I would get L98 exhaust manifolds and run a 3" catback then.. A cam would be more beneficial, and I wouldn't even bother with heads, no sense in sinking all the work/$$$ into a 305. I say just get the catback.... For 3 grand you could drop in a 383 stroker..

 

Stall converter, get a good one. FTI, PI, Circle D, etc. Not a cheapo $199 special.

 

yeah stall converter definetly, I got one from edge racing i recommend them, and depending on what gears you have id get some gears for it too. I've got an '85 with a L69 and its got a stall, built up 2004r and 4.11 gears in it and that really wakes up the car.. motor is all stock except for air cleaner and a little q-jet tuning..

 

To be clear I don't have a problem doing internal work, just that I'm not sure I'd do a cam myself - but after reading more about it maybe I would after all.

Seems cam is probably the best choice. Other posts tell me the 305 is more limited by exhaust than intake so no point in new intake manifold, runners, or TB. The stock cam is pretty average so a new cam should wake it up.

Torque converter sounds ok but not worth doing yet if I'm going to do anything that will change the torque curve as it would be best to match the stall speed.

L98 manifolds is a good idea if I can get them... might be a bit hard to locate for me, or a ridiculous price, not sure.

So new cam, timing gear, valve springs, seals, and roller rockers... new lifters shouldn't be necessary, right? Depending on the cam follow up with a custom chip?

 

Not true, a good converter will wake up anything. Not to mention the gains from shift extension.

 

Can you explain?
How bad is the stock one?
What stall speed would you go for?

 

you got fuel injection itll mess up your computer if u put a cam in it

 

That's a myth as well. If you go with too big of a cam, it will idle poorly and be hard to tune. A well thought out/proper camshaft for the application will work fine with the EFI. He has a MAF car also - they are even more forgiving than SD cars like my 91' when it comes to camshafts.

 

Shift exstension is basically this in a nut shell... with your stock converter let's say for a round # you drop off 2500 RPM on the 1-2 shift. An efficient converter will cut that down to about 1000-1500 RPM on the shift. Thus, keeping you in the power band and helping the car accelerate faster.

The stock converter was designed for gas mileage, not performance. It's fine - for grandma's sedan. Something better will unlock the true potential of the car.

I would go with something in the 2400-2800 range, 10" - lock up. The smaller converter weighs less, which also helps acceleration. You also need to look at STR, stall to torque ratio. IIRC - factory is around 1.8 STR. A higher STR will "hit" harder and multiply the TQ at the crank more.

A quality converter should net you a solid .3 even on a stock/near stock vehicle. In the LS1 world, a good converter and sticky tires will knock .7 - .8 off the 1/4 mile ET's.

IMHO - get a converter and make the car put the power it has to the ground. Then I would have a cam ground that will work well with the factory cylinder heads and restrictive exhaust manifolds. Speaking of manifolds... L98 & LB9 cars share the same exhaust manifolds. There is no difference in them. The L03, LG4 cars have smaller manifolds.

 

X2 on the converter. My IROC has a 10" vigilante tc (2800 rpm stall) and it really woke the car up!!! Also consider some new servo's for the trans. My IROC with the stock 305 TPI motor and a race-built 700r4 runs even with L98 cars. It's all in the trans.