Comparing my L98 to my old 350HO setup, I am down 14 mph in the 1/8th and 19 mph in the 1/4. My 350HO with a flat tappet XE274 went a best of 12.24 @ 111.85

I have asked a few questions, gotten some great advice, but I really feel like with the popularity of LSX motors, that TPI info and builds are getting pretty scarce. I find myself reading about TPI builds and drag cars from 2004, it really feels like the industry has moved on to LSX. And why wouldn't they? My understanding is the heads on my L98 flow under 200 cfm @ .500 lift, my TPI system stops producing power above 4500 rpm, and the cost of parts for this setup (runners, manifolds) are expensive.

The good news is that I was given a set of Vortec heads.

http://www.popularhotrodding.com/eng...k/viewall.html

Let's be honest here, I feel like I could pull the TPI and L98 heads off my motor, bolt on cheap Vortec heads and a good dual plane with a 650 cfm carb, swap camshafts and make well upwards of 400 horsepower. If the magazine builds pull 440 to 450 horsepower with Vortec heads, I don't see why I can't make an honest 400 to 425.

I am just waiting on someone to say "Wait, I did this with my L98 and made XXX horsepower", but it doesn't seem to be the case. My L98 doesn't seem to be one of the factory freak cars that runs in the low 14's stock :shrug:. Thoughts?

 

the tpi was a big stepping stone in the history of the sbc, and thats one of the reasons why i like them. today, they are slugs in terms of performance when compared with the ls motors. but they were a good driving engine in a street car.
you simply can't beat a $500 junkyard ls motor for performance per dollar. if you want to go fast cheap, its probably the best direction to take at this point.

if you could get a set of 180-190cc aluminum heads ported by some place like TEA, you could swap cams along with an airgap intake/holley and make 400+ at the wheels with your engine. you would pretty much need a cam+ head swap on a 5.3 ls motor to make that power.

 

I DID get my L98 running pretty good. I never really bought into the "factory freak" thing. I always believed it was attention to small details that seperated the fast from the slow. Mine was one of the 14.0 cars stock....

With only cylinder heads and a comp 276hr on the stock shortblock and stock TPI I went a 12.27. A swap to a miniram resulted in 11.9s and a 6 mph gain. They just take a bit of patience and the right combination of parts. I plan on keeping this motor to put in an IROC for a fun little street car. I am certain that a simple 10:1 383 with a slightly larger cam and some head work would do an 11.50 with full accessories, street driven, etc. It really depends on what your goals are with the car. A 12 second street car is easily attainable with what you have now. If you want to go faster or are starting with a clean slate, then an LS is perhaps your safest bet. If you are looking for a lot of 1/4 mile mph, the TPI has to go however.

 

The L98 is a typical SBC 350 with the addition of a roller cam and the TPI intake system. GM designed the TPI intake to maximize TQ and mileage, while sacrificing top end HP and revs. The issue is the long runners of the TPI intake - they are going to keep peak hp below 5,500 no matter what you do to it. Switching to a superram moved the hp peak higher without sacrificing too much TQ and a miniram give you all the top end you could ever want while sacrificing the bottom end.

Carb is certainly easier, but the driveability of a good EFI system is hard to beat, not to mention better fuel economy and emmissions.