Jhucks03

Any rough idea how much would need to be machines off to match CC’s? Then, would this make manifold machining necessary?

joe_padavano

Intake manifold matching is a function of port dimensions. It has nothing to do with milling the head for CR. Not all intakes have enough meat for this.

Fun71

In my (limited) experience, big block heads run around 80-84ccs and early small block heads are around 68-70ccs.

Jhucks03

I guess I was meaning if I cut off say .050” will the gasket surfaces still be in the same plane, or will I have to cut the end seal areas of the intake.

cdrod

I don't think you can use BB heads with a stock intake manifold as the intake runners in the BB head are taller than the SB head. I have aluminum heads on my small block Olds which were milled down to 70cc chambers, but I don't know how much material is removed to get to this chamber size. I was told to use the small block Edelbrock 7111 manifold which has "extra" material at the top of the intake port to fit the BB head ports. I still had to machine the head surfaces of the intake manifold so the ports and bolt holes would line up properly.

Jhucks03

Thanks. That’s what I was getting at. I’m aware of using the RPM intake to port-match.

67OAI

You can mill .050" off BB heads safely and that will get you about 5 cc worth of volume taken from the chamber. Now that you've done that, what head gasket are you going to use? The factory head gasket (no longer available) is a thin embossed shim steel piece that measures about .017" or so when torqued in place. The commonly used Felpro head gasket measures about .042" when torqued in place; as you can see, a difference of about .025" which will just about negate that .050" cut off the cylinder head! Even if you cut .100" off the cylinder head it won't help much with that thick head gasket. If you use the thinner MLS (as in Cometic) head gasket to keep the compression up, you will probably need to have the deck surface of the block cut to obtain a good seal. Now that you have done all that, you still shall have to get the intake surface of the heads cut to match with the intake alignment, etc.. Is it worth it?