ok, got a 1994 LT1 vette. I have a K&N filter, open air lid, i am planning on porting and removing the rear screen from the MAF, i have shorty headers in a box (soon to be installed), I want to get the heads ported and polished and match them to the intake and headers, and I want to put flowmaster mufflers on this car(with the original LT1 tips). My questions are:

Can I turn my 48mm throttle body into a 52mm without too much trouble?
Can I remove my catalytic converters without any trouble?
What is the best ECM upgrade scheme?
With the mods I have listed so far, what do you guys think I could be putting to the crank/ground?

what other mods can I do short of stroking, turbos, nitrous (i just plain don't wanna mess with nitrous and turbos and stroking aren't cheap)?

Thanks! :seeya

 

The easiest way to convert your 48mm TB to a 52 is to buy one, usually on an exchange service. It would be quite hard to do with convetional hand tools and get it right. Although it has been done but I don't recommend it.

As for removing the CATs, I can say that the GM CATs are very efficient and flow very well. I and many others on this forum run full CATs. My car in particular is a stroked and supercharged 396LT4 and I have no problems with having the CATs there. For a mild build as you are planning with ported heads and a cam (highly suggested) you won't need to remove them.

You best bet would be to have the heads ported by a reputable porting service such as CNC heads, Advanced Induction, LPE or others. Pete at CNC heads will do you a fantastic job and also will sell you a cam to match your heads. STL94LT1 used his heads/cam combo and is currently pulling over 425 FWHP with his 94 coupe. He too is using shorty headers and a flowmaster exhaust system and a 52mm TB I do beleive.

After getting your heads and cam changed you will need to optimize the PCM tuning to get the most from your mods. However if there are minor mods such as a air filter lid and exhaust, tuning is pretty spot on from GM as delivered. You may find a few lost ponies in there but from the General as delivered the PCM calibrations are pretty good.

Short of stroking the engine, the CNC porting of the heads and intake and the cam swap is the best bang for the buck. Of course there is the supercharger route, but on a stock cast piston engine and if its got lots of miles, you are asking for trouble.

A simple way to make your car quicker is a 4.10:1 gear swap for a M6 car, and if you car is an A4 then a 3.73 gear swap and a convertor will make your car lots quicker. That change alone is worth a few tenths in the 1/4 mile. Much more than a TB or PCM change alone would ever give you. Add that with a CNC head and cam job and you have a potential of a low 12 second or high 11 second street car that still gets 25+ mpg!


[Modified by tjwong, 9:26 PM 10/10/2003]

 

If you are removing your cats, sell the shortys and buy full length headers. There is more performance increase with the Longtubes than shortys by a fairly wide margin.

No need for a 52mm TB at this point.

Change your rear gearing, and youll feel like youve got another 50hp.

At the same time you do the heads, change the cam, and associated valvetrain parts.

 

I thought about gearing changes but I don't wanna lose any top end. With the different gears it would make it more drag car, and i am looking for a ridiculous top end..hopefully 180mph+....btw, any word on what these cars will do stock?

 

Should put out in the ~160mph range, I dont know the exact number for LT1s.

Just how often are you going to need 180mph though.

 

:iagree: Heads/Cam/Gears and a good friend like Tom Wong helping with the tuning is the way to go.

 

:rolleyes:

Doable, but not realistic. My car is daily driven with 3.54 gears....far from a drag strip demon.

 

I agree that gears are the way to go, best mod I;ve done. Vader is right, it's like adding 40 to 50 hp.

Folks have had problems with some of the after market TBs. If you must do a 52 mm TB, check out LPE. They bore out the stock 48mm and a few other tweaks, it's the best fit for TB "replacement".

:seeya

 

OK, assuming i go with 3.73s, how much top end can i expect to lose, how much quarter time can i expect to drop, and how would i adjust my speedo back?

 

I did 3.73s my first mod went from 14.1 to 13.6 did not seem to lose any top end though and it gets there a lot quicker . Ive had it at 148 & had more but the wife got scared . Yes dear .

 

Ive posted a couple of threads on here about my car. With stock unported heads I am getting good results. Later this week Ill post dyno sheets with my car in full tune. It has a crane hyd roller, lt4 springs, tpis long tubes into dual 3" tubing, holley 58mm TB, 30lb injectors.

 

how much would it cost to go to 3.54's? currently i have 2.59's

 

Youre looking at a half-second drop off the ETs if you go to 3.73, just a bit less for the 3.54s.

You would need a Hypertech PP or something like that to reprogram the speedo.