Hi my name is Jay and I am new to tpi but not so new to 3rd gens. I have owned many of z-28's and love everything about third gens. I just purchased a really well taken care of 89 iroc that "unfortunately" someone yanked the OE motor and heads and replaced it with a bone stock gm crate motor 350.

Problem is he didn't leave me the center bolt heads and I am left with the mexican 76cc crap heads.

Question is......since these heads and the center bolt heads are different designs and flow different, wouldnt that throw the pcm outa wack if it werent tuned???

Also the 4 center intake bolts don't line up with these heads.........ticks me off.

Anyway, its great to see so many other f body sufferers like myself out there tryin to make a slow car fast.

P.S. are the 90's model truck vortecs the same as the oe iroc vortecs?......64cc?

 

Welcome aboard thirdgen.org.

The ECM isn't concerned with the difference in heads because it's a mass air flow (MAF) system. It compensates for changes very well.

"Vortec" heads are the heads from '96-'99 trucks. That's the only production use of them. GM found out hot rodders knew what to do with them and started offering them as performance parts, plus added to the line with bigger port, aluminum, etc., versions. You will need that $400 Edelbrock base to use Vortec heads, though.

The '00-later "Vortec" engines are LSx based. Those heads won't fit on your Gen I engine.

(Word to the wise: This is intended to be a family- and work-place friendly Board. Please refrain from "colorful" words and changing such words to get around the Board swear filter. Much appreciated.)

 

Im sorry, I was under the impression that this was "thirdgen.org" not "thirdgen/firstbaptistchurch.org"

I'm sorry I got so "colorful" with my words.

P.S. "****" is not a cussword at all................look it up

 

The information and help available here make it more than worth the little bit of effort it takes to keep it clean.

 

Again I am sorry..............I meant no harm.

I meant the center bolts in my last sentence, not vortec. Are the centerbolts on the chevy trucks the same as the iron center bolts on the iroc???

 

Someone please correct me if im wrong, but the center bolts for you intake maifold are pre 86' and the ones on your iroc are from 89'. After 86' the intake bolt holes are at a different angle. So if you want to adapt the factory tpi setup to your new 350 you'll need a new intake manifold and a larger injector size for it to run properly.

 

Okayu, if you're looking at '87-'95 truck heads, that are assembled, you wont be able to see the high-swirl intake ports, but they don't flow, and don't respond to porting. You can stick the good vortec heads on your short block, or you can go to aluminum heads. Or you can run what you have, of course. If you keep the heads you have, they flow similar to what your car should have, but you're way down on compression. If you haven't changed anything yet, that claimed 8.5:1 is actually just under 8.0:1. If you don't want to grind on your lower intake manifold, then the one from a same-year vette is what you need. Or an aftermarket upgrade like Edelbrock or whichever brand you like. The heads you have are the same as used on the 290 HP crate 350, and they will accept most any aftermarket intake manifold.