John Millican is modifying an intake for me. Anyone know of any differences when using ZZ4 aluminum heads? I can't wait to get this swap done and let this thing breathe. I have a G-tech, so I should be able to get some before/after #'s for a LT4 hot cammed ZZ4 with LTR vs. LT1.

 

The zz4 heads contain the pre-86 bolt pattern for sbc heads. SHould be no problem. I believe he cuts them for both style heads.

 

Ah, that's what we needed to know. Hee i thought the NEW ZZ4 would have the newer bolt pattern intake/head on the center two intake bolts.
So it's the old style huh?

 

John, I'll get a chance to confirm it in the morning. I can't believe I was too busy today to even go take a look.

 

Ya they are the old style the zz4 heads are the same as the L98 58cc alumminum vet heads.

 

That's weird, so these heads have the centerbolts which is 87-up, but have the bolt pattern of pre-86. It's hard for me to tell for sure with these runners in the way, but take a look at the pic below. It looks to me like the center bolts are not angled. I'm guessing they would be more toward to the South end of the intake slot if they were.

 

yes they are old style heads.

 

Earl is right the zz4 heads are the same as the corvette l98 heads, but with upgraded springs and stuff, says so right in the gm performance parts manual.

This high-permormance cylinder head assembly is used exclusively on High Output 5.7-liter small block V8 engines. Unlike production Corvette cylinder heads, it is outfitted with specil heavy-duty valve springs.

Straight from the pace website

But I believe that for a while places like Scoggin-Dickey were offering them redrilled for the old bolt pattern, so if it's a used set of heads that's possible. Easy to check though, if the bolt holes aren't at 90* to the intake face it's the newer style, you can just eyeball that the difference is pretty big.
John