so i acquired some TPI stuff that the PO got from some guy...years back...and he is pretty sure its off of a late 80's Camaro. i did get an aluminum distributor cover out of the deal and i wanted the upper plenum so i can port it out and put it on my 89 Formula 350 while not having to run the risk ruining the one i have, or even have to bother taking it off in the meantime.

however, when i see these listed for sale, they are usually subdivided into 85-88 and 89-92. i see no exterior difference. are they not interchangeable? what is the difference? based on the pics below, does anyone recognize this plenum as being either 85-88 or 89-92?

thank you.

 

I know the MAP cars have the MAP sensor attached via a bolt that threads into the passenger side towards the rear of the intake plenum. I would imagine that's not on the 85-88...

 

I have a plenum that is supposed to be an 89, casting # is 10108468.

As far as the diff between years, the plenum is the least of the changes. The bigger differences are in the runner and the base, mostly due to the elimination of the 9th injector in 89 and it's related hardware such as the extra port in the intake base for the cold start time delay switch.

 

One major difference between the two upper plenums is the IAC airflow path. Note the triangle opening in the pictures for the IAC airflow path. 1989+ upper plenums don't have that path as the IAC airflow is directed through the throttle blade paths. Mixing two different ones (1989+ upper plenum with a pre-1988 throttle body) can result in loss of IAC functions which means idle and fast idle control issues as the ECM can't control the idle.

 

thanks for mentioning that... I asked a buddy awhile ago about that, and he said there was no difference. Now i see the difference and i kinda thought there was. I'm sure in my parts catalog there different part numbers to from 85-88 and 89-92

 

The plenum in the pic is a 86. They all have a date code on them.
I have a TPI throttle body that has a date code of 84 on it, soo they cast/built them B4 the model year or close to it but always b4 the car/motors build date.
The aluminum cover came on corvettes only and uses a different screw than the plastic cover.

 

Also you should be able to use the late throttle body on the early plenum, but would have to modify an early to use on a late for sure... might start kind of hard but it should be doable...