Just a quick question....would the addition of headers increase the powerband of a TPI engine beyond the infamous 4500RPM "wall"?

 

The bigger 1's, like the 1 3/4's will give more upper RPM power.

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89 RS

Looking For:
87 IROC-Z28 350 TPI

 

That "wall" is caused more by the ignition system, and the inability for the injectors and such to be able to keep up with the demands of the engine past that point, not the exhaust.

But, that's not to say that the system wouldn't help higher rpm power, because it would.

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89 iroc-z 305 tbi
k&n filtercharger, open element air filter. nuffin' else

 

What causes this is the length of the runners and other things that could use porting in the plenum. While the design (of the runners more) is great for really good lower RPM Torque, its not that good for higher RPM HP. This is why many switch to the MR. Can u get high HP with a fully modified TPI setup?? Yes, but not like a MR. The TPI setup will produce better Torque than a MR though. I'd rather have the car with the TQ (TPI) than the HP (MR) for just the feel of lots of TQ, and it'll make a better street car. I want a car that runs 11's-12's with lots of TQ instead of lots of HP for those reasons.

Porting and modding to bigger sizes (runners, exahust) will assist your cause some, but TPI will always be better for TQ than HP.

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89 RS

Looking For:
87 IROC-Z28 350 TPI



[This message has been edited by IROCZTWENTYGR8 (edited July 07, 2001).]