What is the most restricting part of the stock TPI?
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Joined: Jul 1999
Posts: 268
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From: Indianapolis, IN
Car: 89 Formula T-Top
Engine: 388 MiniramII
Transmission: T-56
Axle/Gears: 3.27
What is the most restricting part of the stock TPI?
I want to upgrade my TPI for my 383 so it can get more air. Between the throttle body, runners, plenum and intake manifold which part is most restricting and what is second, third and fourth?
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'89 Formula 383 TPI
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'89 Formula 383 TPI
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The EGR walls behind the TB make for a nice obstacle, but the worst piece is the base. The EGR walls are easy enough to grind down, then all you need is different runners. The TB flows quite a bit stock, and its much easier to change than the rest so you can save that for last.
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As Madmax said, after the EGR walls are gone, the plenum becomes much less a restriction.
Lower intake is a big restriction, runners next, and TB is the least of a restriction. Plenum should be port matched to the runners for best performance, obviously.
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-Bill
1991 Z28, 305TPI, 5-speed,
AS&M ported & polished intake, AS&M polished LTRs, AS&M port matched plenum, TPIS 52mm TB, Richmond 3.73s, SSM SFCs, SLP LCAs, SLP panhard, ATR 3" exhaust, MSD 6al, Taylor 10mm wires, SLP PROM, and a host of other stuff.
Lower intake is a big restriction, runners next, and TB is the least of a restriction. Plenum should be port matched to the runners for best performance, obviously.
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-Bill
1991 Z28, 305TPI, 5-speed,
AS&M ported & polished intake, AS&M polished LTRs, AS&M port matched plenum, TPIS 52mm TB, Richmond 3.73s, SSM SFCs, SLP LCAs, SLP panhard, ATR 3" exhaust, MSD 6al, Taylor 10mm wires, SLP PROM, and a host of other stuff.
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Joined: Jul 1999
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From: md.
I remembered when I built a 383 for my 91 GTA. I first installed the entire stock TPI and manifolds on the car.. It only ran .3 tenths faster...Next I installed SLP headers with the stock TPI.. I gained an additional .3 tenths.... I next added a Superram and 58mm TB and gained .8 additional tenths.
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Joined: Apr 2000
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From: Ocala, Florida-USA
First-the base,for sure.
Second-the plenum...EGR blocks should be ported and blended.
Third-runners....depending on your combination. ex: gear ratio, converter ,camshaft etc.
Hope this gives you some insight.........Later, -HAMMER-
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1987 GTA,Black&Sinister.
383 ci TPI,700R4, 12 bolt,3.73:1,SSM lift kit,
home-made cold air induction.12.20's,no juice......yet
Second-the plenum...EGR blocks should be ported and blended.
Third-runners....depending on your combination. ex: gear ratio, converter ,camshaft etc.
Hope this gives you some insight.........Later, -HAMMER-
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1987 GTA,Black&Sinister.
383 ci TPI,700R4, 12 bolt,3.73:1,SSM lift kit,
home-made cold air induction.12.20's,no juice......yet
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Joined: Jul 1999
Posts: 126
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From: Lindenhurst, IL USA
good insight Hammer....you got that car moving BTW...
can you tell us your set up as far as the motor goes? thanks there is not many people around with that kinda NA power and it will give some Guidelines to follow
Matt
can you tell us your set up as far as the motor goes? thanks there is not many people around with that kinda NA power and it will give some Guidelines to follow
Matt
Dont worry, i wont tell the race car, hehe 
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