I was wondering, if it would be ok to mix cylinder heads with two different casting numbers. I have 083 heads on my car and one of them is cracked. Would I have to use a matching pair or is it ok to mix them as long as I can retain the original compression ratio?

I would tend to think that's a bad idea. Even keeping the compression ratio the same head to head, each with have its own flow profile that will almost certainly be different. Your engine will make more power on one side than the other. Maybe it's not as bad as I seem to think, but all the same, I wouldn't do it.

It's best to have matching heads. There's not really a whole lot of reason not to match them.

Thanks for the response guys! I was just wondering about that. I will be looking for a set of matching heads but I wanted to know if I ever came across a head witht he same specs as my 083 head if it would work. Do you guys know if heads off of a 85 Vette would work with my 88 TPI Manifold? I have an opportunity to get a matching set off of an 85 Vette. I think they are iron heads.

Yeah, they should work fine.

Thanks buddy! I just want to make sure. Cause I heard somewhere that they might not match up. Oh wait. I just remembered Pre-87 Was flat tappet cam and 87- is a roller. I have a roller block, would the 85 head still work?

Yeah they'll work, the heads don't care what lifters your block has. Then only heads you can't use are vortecs (unless you change your intake) LT-1 heads or any of the gen III/IV stuff.

Alright, sounds good. Thanks again dude!

No problem. Just a note, I said you could use 55 heads, meaning that they'd accept the intake. I wouldn't use them because they have no accessory bolt holes. :P

center bolt holes on the intakes are different 87 and up, but inkakes can be modifide slightly to make them work

The center bolts are a slightly different angle, correct? Just slot the intake holes a little and no issue.

I had a 350 in a truck that had two diff 305 heads

one had 1.78 and the other 1.86 valves

yeah!

it actually ran stronger with the smog 350 heads w/a little carbite work.

engines like balance

Yes you can "slot" the holes. But do this slowly and carefully and check it often against the heads your best off using a Burr type bit and not a drill bit. First one I ever did I went too far on the inside of the intake where the gasket seals and had to repair that goof-up so take your time if you do this