I just dumped lots of money into a brand new 350 on a 1990 TPI Firebird. Even with a custom chip it still does not move the way I expected.

How big of a difference do the after market
runners and base make? seems like i got everything else.
Is it possible that the 2.73 rear end and stock torque converter are eating up lots of power with the 224-230@.50 cam?


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1990 TA 350 TPI
SPORTSMAN II HEADS
COMP CAMS 224-230@.50
52MM THROTTLE BODY
24LB INJECTORS

 

AG350,

Welcome aboard!

The components need to be matched to provide the best performance. The W/P SII heads are good for flow over a fairly wide RPM range, but are not really designed to support torque at low RPMs like the TPI system is designed to do. The Comp XTreme Energy cam will also cost you some low end torque but more than make up for that loss at the upper end of the RPM band. The dysfunctional nature of the system is likely due to the TPI not matching well to the heads and cam. Even with the larger throttle body, the plenum and runners are designed and tuned for low volume, high velocity flow. The heads and cam are designed to provide just the opposite.

And your suspicions about the stock torque converter and low rear gear ratio are correct. Keeping the RPMs low due to the tight converter and low rear end is keeping you out of the power RPM range longer than you should be. The converter is going to make the biggest difference, but gears will help some. Once you increse RPMs, you'll need to suport that power with a better-breathing induction system.

This does not mean that you need to need to trash the TPI system, just overcome some of the restrictions. Porting the plenum and gasket matching the runners and base plate are a good start. If you have a "real-phat" checkbook, a Mini Ram is a good solution. Short of that, removing some of the system restrictions will certainly provide some gains.

Check the message archives for plenum porting, and similar threads.

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Later,
Vader
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"Let the bodies hit the floor!"
Adobe Acrobat Reader

 

Your combo is mismatched.

How fast do you want to go and how much money do you have to spend?

 

thanks
porting and gasket matching were going to be my next project. hopefully that will help.
I was worried that too much grinding on the intake might murder some more low end.

At the moment money is an issue so gears and TC will have to wait.

 

the converter is gonna make quite a bit of difference. if i was you, id save up and do the converter and 3.73 gears at the same time, and the first time you stand on it, you will have a grin from ear to ear.