I have an '89 ASC GTA, L98 and i'm thinking of polishing the plenum.. I also have a spare '86 Plenum and was thinking of polishing that so there's no downtime.
Will that '86 Plenum work on the '89 setup with no cold start injector?

 

Just open your hood and compare both of them. Look carefully and you should see or not see the difference.

Good luck!

 

The plenum itself should not be different.The runners are different, however. The drivers side runner has provisions for the CS Inejctor

 

I'm tired, but IIRC you can use an early plenum on a late car, but not vv. The early plenum has some IAC stuff cast into it, later plenums don;t as all the IAC passages are in the TB.
So yes, it should work. If i'm wrong, someone correct me...

 

What is the ASC GTA. I know what a GTA is obviously but what does the ASC stand for.

 

ASC = american sunroof company, they did the majority of the thirdgen convertibles (and the only authorized verts), of course 89 bird verts weren't factory authorized anyway, they were sent by the customer for conversion, thus calling it an ASC GTA has some meaning (since other companies were doing the conversions back then, just saying 89 GTA vert wouldn't be specific, but saying 92 GTA vert would since they were factory auth. by that point)

 

The plenum IS different. But you can use an 85-88 plenum in a 89 application. You cannot use an 89 plenum in an 85-88 application.


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1989 IROC-Z 5.7L
NOS 5151 150HP kit
ProBuilt 700R4, PI Vigilante 2800 stall lockup
Baer Brakes 12" Sport System