I have an 88 GTA with the 350 and just bought a used set of TPIS semi-siamised runners that came with a fully ported plenum. This setup was used on an 88 vette. The plenum on my car has 2 raised passages on the bottom that I think is for the EGR and cold start system, but the plenum that came with the runners only has 1 of the raised sections which is for the EGR. It has the hole for the MAP sensor that I thought I could plug if this plenum will work with my MAF system. Also the front of the plenum has been opened up looks like for a large single blade throttle body.Will this work with my stock throttle body?

Hmmm, doesn't sound too good.. The center divider should really be there. I don't see why anyone would remove the material in the middle for a stock or 52mm t-body. All I know is that Vader tells you not to remove any of the material in the center divider in his tech. article on porting the plenum, as it will cause increased turbulence coming into the plenum. As for the other stuff I am not too sure.

can anyone help with these questions before I put this setup on my car?

Could you just use your stock plenum and have it ported to match the new runners?

I'm porting plenums for $60 each, and I leave the center divider there.

however, in thinking about it, I don;t think the turbulence arguement really holds up. The reason is that the plenum, for all intents and purposes, is a log! There is a bunch of turbulence in there from reversion at each of the runners, and all the various bumps that hold the runner bolts. The divider is FLAT on the back anyway. Just as flat as the back of the throttle body. Thus, you move the flat only another quarter-inch outwards to the back of the throttle body when you remove the divider.


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Daniel Burk
http://www.isthq.com/~dan/fcar.html
'84 Trans Am WS6/L69
KB SFC, Moser axles, Torsen Diff. PST suspension, Braided stainless brake lines, Koni struts, 11-inch rear disks,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.
1.05g skidpad verified.
New best E/T! 14.039 at 100.82 MPH in 41 degree air at Stanton, Michigan.