Fel Pro 1213

512Stroker said
I have successfully used .030 brass sheet shim stock between the head and the gasket to block off the cross over. Cut to fit with a little over lap and some hi temp silicone and your done.

D-mailman said
I use stainless steel shim .021 thick, picked up from metal shop cheap. Cut to fit allowing about .200 overlap and using contact cement like super glue to hold the plates in place , works great, I have to pry them off with a screw driver when I have to remove the plates . It works for me .

I've always thought that the shim material would possibly create a vacuum leak. But obviously not. I may try this before I go the epoxy route.
I measured temps on the manifold with a laser temp thingee, (now, before blocking the heat) so that I could possibly tell if a particular block off burned through.