If you mill the heads down to increase compression, what would be the best way to make the intake manifold seal? Use 2 intake manifold gaskets per side? RTV a custom phenolic spacer? Not that I'm going to be doing it soon, I've just wondered if and what has been done before.

 

I think the consensus is to have the Intake manifold milled to match. Most machine shops can do this

 

would you mill the manifold bottom where it meets the block?

 

yes. if you tried to use a spacer on the sides or something, the ports wouldn't line up properly. how much do you plan to mill the heads?

 

Just enough to bump up the compression a bit but not interfere with the valves. I'd have to do some math and measuring first. Its a 3.1 and when I put it together it seemed like the pistons were really close to the top. It still doesn't seem like it would work by just removing material from the manifold.

 

It works. If you imagine that the heads and manifold are bolted together and you were to remove the same profile as the top of the block out of the three parts, it would pull the heads and manifold down closer to the crank respectively.