Hey everyone... I will be starting on the porting of my factory 1988 plenum. I hear a lot about the EGR wall removal. I spent quite a long time looking at the plenum trying to figure out what theck you all mean by the EGR wall, and what kind of benefit it would have removing it. As far as I can see, the EGR passage come through the runners, in the plenum, and routed in lower passage to the front of the plenum (behind the TB). Do you remove the whole lower passage? Does anyone have CLEAR pictures of what to do with the EGR wall? I have seen others... but they just didn;t cut it.

Your help is greatly appreciated.

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1988 Pontiac Trans Am GTA L98 5.7L, Black on Black with 114,000kms.

Best ET 14.559 @ 95.25MPH
Custom 3" Stainless Exhaust Y-Pipe back (High flow Cat and Flowmaster Mufler)

 

The wall that is refered to is at the bottom of the plenum right behind the throttle body openings. They're actually little humps, and if you look close you can see the egr outlets just behind them. You can knock those down quite a bit and do some polishing along the walls.

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'87GTA w/ SLP Cold Air, MSD Coil, Airfoil, Gutted MAF, AFPR, TES Headers, HI-FLOW CAT, Flowmaster Catback, Energy Suspension Master Bushing Kit

 

I'll have to take a closer look.... I am afraid of one thing... does the IAC go through the plenum? Or is it routed through the TB?

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1988 Pontiac Trans Am GTA L98 5.7L, Black on Black with 114,000kms.

Best ET 14.559 @ 95.25MPH
Custom 3" Stainless Exhaust Y-Pipe back (High flow Cat and Flowmaster Mufler)

 

There are no IAC passages in the plenum. They are only in the throttle body.

 

Ahhhhh... that is a good thing to know ) One quesion then... What is the triangular shaped port where the TB bolts up to the plenum? This is what made me think that the IAC passages enter the plenum via this triangular port.

 

Pre-'89 has the IAC passage through the plenum...that's the triangle hole. '89-'92 use a different TB.

 

Ahhhhh..... It's al clear to me now... So I do have to be careful when grinding down that EGR wall? I am gonna start it this week hopefully... I'll let ya's know if I run into a snag.


Thanx a lot!!!

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1988 Pontiac Trans Am GTA L98 5.7L, Black on Black with 114,000kms.

Best ET 14.559 @ 95.25MPH
Custom 3" Stainless Exhaust Y-Pipe back (High flow Cat and Flowmaster Mufler)

 

It should look like this:
The EGR wall was at the top of the pic. (plenum is upside down)

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Bob '89 Ram Air Formula 350LT1

And until that time when death won't wait, let each man rage against his fate. (O'neill)
My car's homepage
Reader's Ride

 

Hey RCR, thanx for the picture, I've checked your website multiple times... but I could never orient myself to those pics. Do I have to be careful when I grind away the EGR wall since the IAC passage is there as well?

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1988 Pontiac Trans Am GTA L98 5.7L, Black on Black with 114,000kms.

Best ET 14.559 @ 95.25MPH
Custom 3" Stainless Exhaust Y-Pipe back (High flow Cat and Flowmaster Mufler)

 

Here's some more pics for you!








Does this help?


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Daniel Burk
View my third-gen hobbyist performance page!
View my reader's ride!
'84 Trans Am WS6/L69
KB SFC, Moser axles, Torsen Diff., Spohn Adj. torque arm,
Ported 305 heads w/1.94"intake valves, Comp Cams XE262H, Griffen alum. radiator,
Turbine Technologies 2500 stall converter, underdrive pulleys, Crane Hi-6 & more.
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Best of 14.039 at 100.82 MPH in Stanton, MI
New!Full 1LE brake upgrade! Details at website above.

 

Hey, that is a pefect picture!! Thanx.... hey, sounds like you have a lot done to your car, yet your ET seems slow.. is it a 305 or 350? I was hoping to get to high 13's... 13.5 to 14.2 but.. if you're not hitting 13's with your setup... I have another thing coming to me... we'll see

Thanx Again

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1988 Pontiac Trans Am GTA L98 5.7L, Black on Black with 114,000kms.

Best ET 14.559 @ 95.25MPH
Custom 3" Stainless Exhaust Y-Pipe back (High flow Cat and Flowmaster Mufler)

 

Dan's still running his original 305. I think he still has a 383 in the works, though.

 

I don't think ANYBODY would put 305 heads on a 350.

 

I agree with you.. but.. it was kind of redundant saying 305 heads on a 305... I have heard of 305 heads on a 350 though, to boost up compression. A buddy of mine did it on an older 350.. was kinda quick for a really low budget engine.

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1988 Pontiac Trans Am GTA L98 5.7L, Black on Black with 114,000kms.

Best ET 14.559 @ 95.25MPH
Custom 3" Stainless Exhaust Y-Pipe back (High flow Cat and Flowmaster Mufler)

 

Yup, I outsourced my SIG to the department of the redundancy department ...

Actually, if I wrote "ported heads w/ 1.94 intake valve", people would say "so what?? Isnt 1.94's stock for a 350 head?" Which is true. However a 305 head came with 1.84 intake valves. I've increased the valve size, and reworked the bowls extensively. I've also unshrouded the exhaust valve and sculpted the combustion chamber. It seems to work: It's consistantly at 100 MPH in the quarter mile, gets 21 MPG on the highway, and revs to 6000 RPM with no oil burning or other dramas. The block is 136,000 miles stock, except for the flycutting of the pistons to clear the bigger valves. I'm still running a computer controlled Quadrajet but hope to go EFI for '02.

...and I do have a 385 shortblock at the engine shop. Its been there for a year and he's finally moved the parts into the machining area for work this month.

It's an all-forged, internally balanced motor with 6-inch H-beam rods, 4340 crank, Lunati lightweight pistons, etcetera. 10.5:1 compression, and a big, bad nitrous-fed Miniram. It should do 510 HP without the nitrous. That's the prediction of EA Pro, as simulated for me by Jim Sleeper of Sleeper Suspension Developments in LA, California.

 

Well... I noticed the larger valve size.. which kinda led me to believe maybe you put them on a 350, cause then you would have stock 350 flow with more compression.

The new engine sounds like it'll be a blast

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1988 Pontiac Trans Am GTA L98 5.7L, Black on Black with 114,000kms.

Best ET 14.559 @ 95.25MPH
Custom 3" Stainless Exhaust Y-Pipe back (High flow Cat and Flowmaster Mufler)