You'll also need to slot the base manifold's bolt holes as the aluminum head's mounting holes are slightly higher; but, that's really the only diff.
Hey, Jeb: Good to see you here.
I was wondering how about the Vortec heads that so many guys ask about. I know that slotting the intake manifold bolt holes is needed to allow the manifold to boltup but does this effect the port alignment.
You outta see the problems we've been having trying to get a TPIS Miniram to bolt up to set of Brodix 15 degree heads. I mean NOTHING aligns, not intake port, water ports, bolt holes, and the end gaps are so big you can put your index finger in it.
Umm...Yeah, I can imagine you're having a problem. A customer wanted to use a set of 15 degree Pro Action heads on his 434 with a MiniRam. I mocked everything up and told him that I was going to have to cut the flange off the runners, rework everything and then have my welder TIG it back together; it was gonna be expensive. Instead I got him a Pro Action single plane manifold and welded EFI bungs in it!! Much nicer, much easier, and MUCH CHEAPER!! The Vortecs are a totally different animal than the ZZ4's BTW. They have a completely different bolt angle than any other SBC head, they're verticle. You actually either have to buy a specific manifold for em (Scoggin is now selling a big-mouth TPI base for the Vortecs) or weld up the holes and re-drill... PITA!!! Really the only diff between the aluminum heads and the old 882's that were used on the early TPI's is the angle of the hole; a lot of aftermarket base manifolds already come with the elongated holes to fit both later aluminum heads and early (pre-86) applications.
PS- Good to see you here too, Jake!!
Yep, Jeb, that's what had to be done for a 434 I'm doing. Thankfully all this is way outside my area of expertise; Bob Jones' has had the headache with this mod.
That manifold has been cut open so many times and re-welded that it's a wonder it's still able to hang together.
First it was to port it to remove the turbulance that set in at just over 320 CFM; then it became a matter of improving the flow even more so that it didn't present a restriction to the heads, which flowed over 340.
Then came the angle problem with the bolt hole mismatch.
So the manifold got shipped to us from CA for me to mock up and the water ports weren't even close to covering the water ports in the heads, so back to CA they went.
Latest word is that all that's been fixed and the heads are due here anyday. The manifold is being held back for lots of photos and may be featured in one of the car mags.
What a nightmare, but at least all the bugs are out incase anyone needs those mods in the future.
Didn't see this mentioned but the alum L98 heads never changed as far as intake bolt pattern goes. Only the iron head L98 motors (F-bdy) changed on the center intake bolts. An iron head Vette L98 intake will bolt right up to a ZZ4 (L98 alum) head. The EGR problem mentioned above becomes obvious when you realize the ZZ4 heads have no EGR ports. Just wanted to drop that in here. -Jeff