tonight i tried to fill the cavities with JB weld. It was very messy. The two cavities connect and I had JB weld running out. After taping off one side, it went well. It is hard to tell by the pictures but the cavities you see are on a totally different level than the actual intake runners. I am a little nervous about the temp getting too high, but JB Weld says its good for up to 600deg. So, we'll see.
The key is going to be keeping the heat riser block-off plate from burning/eroding away. If you can do that the filled port should survive. I have seen similar thin block-off shims fail and burn up the epoxy on the other side. As long as you have the mill why don't you take .062" off the face of the heat riser and use a 1/16 stainless shim block-off plate. That way you will be safe and avoid a teardown hassle to repair it in the future. A little red silicone hi-temp sealer would be good insurance too.
Good luck with the project. Let us know how it works.
