fmsracing

This web site has been helpful in the past with my projects, so I wanted to share with everyone my results from working on my TPI plenum. I got the idea from some older articles where a few manufactures had made additional HP by completely making a new plenum for better flow. As I looked at the TPI plenum I noticed that the runners did not have a level shot at the throttle body opening. The runners (especially the passenger side front runners) were substantially higher up in relationship to the throttle body opening. Therefore, the air flow had to go both back and up, creating a sharp bend. Also, the rear drivers side opening from the plenum has always bothered me because of the sharp bend at the rear of the plenum to clear the distributor. So I decided to try to correct these issues and my results were awesome. I achieved 17 RWHP and 21 ft. lbs over a heavily ported stock style TPI plenum on a heavily modified 383, with no other changes. My plenum will clear all the stock hardware, including an aftermarket fuel pressure regulator (although it's tight). If anyone wants more pics, just email me. Her is a link to the pics: http://home.satx.rr.com/texaslawyers

Jim85IROC

iTrader: (2)

I'm having a hard time seeing where you changed any airflow paths. It looks to me like you just increased the plenum volume. Either way, your work obviously paid off!

fmsracing

It is probably hard to see from the pics, but the transition angles from the runner ports to the throttle body openings are much more gentle. Also, since we know that more than one intake valve is open at one time, with a larger plenum the incoming air does not to have to compete for the limited pathway space in a stock plenum has and thus allowing for softer angles in the plenum.

1989GTATransAm

iTrader: (3)

Very good. The dyno results tell the tale. I will have to take another look at mine. Allen

vortec77

Hey nice job, :hail: . Ever think of just siamesing the plenum? I read someone on here did it, and i think they got good results too because they also had siamesed high flow runners. Dont know the result #'s though.

89 Iroc Z

How does the distributor fit in there with the extended back of the plenum? Do you have a pic of it on the engine?

fmsracing

I don't have any pics, but there is about .200ths clearance between the plenum and the distributor. The distributor cap and the distributor itself can be removed without removing the plenum, if you have some patience.

87350IROC

iTrader: (2)

I'm having a hard time believing that clears the EGR valve.

89 Iroc Z

Can you post the dyno graphs, I am interested to see the before and after curve.

fmsracing

I did not think about the EGR valve... I have not seen that thing in so long I forgot my car had one. No, it will not clear the EGR. A lot of people have contacted me about this plenum and about selling it. I have it off the car now because I am going to a carb setup and I have decided to sell it on ebay. Here is the link for anyone interested



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Do not sell your stuff on the forums.

fmsracing

After several emails, I will try to answer them all. I have had several emails from thirdgen members about ending the auction early for an outright purchase price. I am sorry, I can't do that because there is already a bidder and it would not be fair to that person. Also, I will include the dyno sheet to the winning bidder, I just don't have a scanner, if I did I would post it now. The engine I had this plenum on was a 383 with a solid roller with a duration of 236 at .050ths, 195 AFRs with the competition porting, 11.0 CR, AS&M SS runners that were extrude honed, an extrude honed TPIS base and a lot of engine coating and attention to details. The car dynoed at 387RWHP 422 TQ. There are NO vacuum leaks at all. Thanks for all the emails and good luck.