ok i just got a 91z with a 305 tpi, for now, im gonna leave it 305 until i blow the biatch up and then i have a 383 im putting in it. now i have a couple questions, is the 350 tpi cam and the 305 tpi cam any different? i want to run nitrous on it and i know the l98 cam is pretty decent for nitrous. secondly do you have to use tpi specific heads or will any set of aftermarket heads bolt up to it? (excluding vortec obviously), anyone know about what the rear axle gear ratio was stock in these cars? and full street trim on drag radials and skinnies with a 100 shot can i get 13's with ideal conditions? car is auto btw, anyway thanks in advance for the help!

 

All TPI cars from '90-92 had the same L98 cam. It's been proven by a few people who removed the cam and degreed it....same as L98.

Are you asking if you need specific heads to run nitrous? No, if you are using a moderate shot. If you go crazy, you'll need more than a set of heads for a big shot. 100shot will work fine with stock heads, or so I have read.

Now the rear is easy to tell, put the car is 3rd and go to 70mph, maybe hit cruise control, and see where the RPMs are at. If it's around 2700, you have 2.73's. If around 3200, you have 3.23's. Whether or not you have posi, do a burnout and see if you have 2 streaks or just jack it up on side, and turn the wheel in nuetral with parking brake off. If it turns with the other wheel planted, you have a 1-wheel-peeler. If it doesn't turn, you have posi.

With a 100 shot, and depending if the car has 3.23's and you can drive and hit the shot once you get into 2nd, you might get 13's. Auto Lb9's are good for mid 15's.

 

i meant just aftermarket heads in general and fitiment to the tpi, can any set of aftermarket sbc heads fit the engine or do i need tpi specific heads to fit it, nitrous has nothing to do with that question

 

Ahhhh, I see. I do know that starting in 1987 they changed the bolt angle to the head and intake. Other than that, I can't answer head questions as I am still learning that. I know World Torquer heads now makes heads for 305's. Also, a popular head swap for 305 guys is Vette aluminum heads. They have the 58cc combustion chambers that the 081 Lb9 heads have, but the valve size of the L98 heads.

 

Also the 1989 305 ( with 5 speed ) had the L-98 cam . 1989 was the biggest cam for the thirdgen's . If you are planning on buying heads , save them for the 383 build , as you don't have many options for the 305 .