johndinu

Hi,
Took off my throttle body (car is 89 gta 350) and noticed the plenum does not have that triangular shaped opening in between and under the two round openings... Was wondering what's up with that?
Are like two kinds of tpi plenums out there, with and without that thing?
Obviously the gasket has an opening there and the corresponding cavity in the throttle body is not sealed.
so air finds its way into the plenum... dunno if that's for air or exhaust gas recirculation...
thanks

8Mike9

85 to '88 and '89 to '92...two different ones, but I forget which is which

johndinu

ok thanks for the reply.
now are there specific tb to plenum gaskets to account for the differences?
in my case the IAC air goes thru the gap in between the tb and plenum not sealed off by the gasket... I guess that's normal, otherwise the engine would not idle
thanks

8Mike9

Hopefully someone will chime in...it's been ages since I looked at the two..but I do believe the IAC passages are different.

I have a few TB's and plenums in the shop and will look at them later today and see what I have.

VincentZ28

iTrader: (2)

There are 3 different plenums. 85-88, 89, 90-92. The 89 is a one year only.

85Special

85-88 has the dreaded 9th injector port.... Dun Dun Dunnn. I can't wait to plug mine off. 89 was no 9th. 90-92 was MAP instead of MAF??? Think that's right.

8Mike9

I think the only difference in 89 vs the SD plenums is a hole/fitting for the MAP sensor on the SD's.
Pretty sure the rest of the casting is the same, or is some else different as well?

johndinu

ok, just checked, the tb gaskets are indeed different. for the 89+ (without iac passage in the plenum) the tb gasket it's opened in the sense that the two tb openings communicate. the earler style, the tb openigs do not communicate.
thanks everyone!