I need to instal l a new plenum on my 89 305 tpi because previous owner had cross threaded two of the bolts that connect the runners to the plenum. I have a plenum off a 86 tpi and I was wandering if it will work on my 89. Tpi parts list a plenum and the only year that it shows it will fit is 89 so that makes me think that it is different than any other year model.

 

id bet its something like the MAT sensor isnt in the same spot as before. what you should do is compare them side by side...and see if itll work.

if it doesnt work, why not use HELI-COIL kit to fix it. in fact a helicoil inside that hole would be stronger than stock...i install helicoil on every aluminum part i come across.

 

Why dont you just re tap the holes with a tap and die set, it will be like new.

 

85-88 plenums are compatible with each other. 89 is stand alone, and 90-92 are compatible. You probably could, but you shouldnt, use an 86 plenum for an 89 because the 86 has the IAC passages that do not line up. It also has the cold start passages in it, would could be a huge vacuum hole.

 

if your going to use an 86 plenum, you need to use a 85-88 driver side runner with it. on those years, they had a "cold start" valve. it's basically an extra injector. the 89's didn't have these. your 89 runners wouldn't match the 86 plenum in one spot: extra hole on the plenum for air flow.
if you had the 86 plenum and 86 driver side runner, you would also need to seal/plug the hole (not difficult, ebay has some plugs for it) on the runner where the extra injector was.
if you don't have the plenum yet or the correct runner, you might be better off trying to fix what you have. if you simply don't feel comfortable trying to fix it, just get the plenum and the correct runner, plug the hole, and you should be just fine.

 

I think I will fix the correct Plenum it won' be that big of a deal to retap the bolt hole I just thought if they would interchange it would be easier since the 86 plenum was removed and cleaned up thanks for the info.