Blocking the heat crossover, IN the head.

I block them off, worth it to me. Street manors are good. There is a reason why head and manifold manufactures go to the trouble and expense to cast performance heads and manifolds without that crossover . I use stainless sheet .021 thick. I cut a piece the same exact shape as the opening but .100 larger on all sides , use contact cement to glue them to the head over the opening, let that set up and use your usual manifold gasket . NEVER had any issues at all doing it this way since 1987. had it apart many times no issues. To me that is THE easy way, no melting old pistons,..no grinding in ports,..same gaskets. Shims .021 thick will not create any leaks and is far enough from the ports to not cause any issues there. 20 min. you can do it. JMHO. With experience.

Terry