Restoring 1967 225. After milling mating surfaces of heat riser, surfaces now have about 3/8" gap. What is fix for a proper gasket to vill this void after manifolds are properly aligned and bolted to block? Thanks for ay help.

Bill

A 3/8 gap is a lot... something is not right.
See the manifold installation article for some basic info.
http://www.slantsix.org/articles/Slant_ ... lation.htm

It sounds like the manifold(s) were warped to start with and the "milling" could not correct all the warpage.
There is no gasket that can fill that much gap so you may need to find a different manifold.
DD

Wow, yeah, that's a large gap. This gap is between the bottom of the intake and the top of the exhaust? Sounds like maybe too much milling was done. If that's the case, you'll need to start over with another set of manifolds.

It is very much worth your while to get the good gaskets for the manifolds-to-head and intake-to-exhaust junctions, but even these cannot compensate for a 3/8" gap.

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Thanks to all who responded, especially with the reference article. I believe the machine shop went overboard. I have a used manifold set on the way, which will also allow me to replace all the missing trangular washers and other hardware. Thanks again!