Cylinder head heat crossover?

[Rory McNeil]

On my 390/427/428 FE Fords, I have always blocked the exhaust crossover opening in the intake gaskets with a piece of an old butter knife, trimmed to fit inside the slot in the gasket. I have tried the gaskets with the unopened crossover holes, but they always burnt thru in short order. I always found it interesting that NHRA will not allow you to fill the head passage down into the bowl, yet the approved Edelbrock heads have no provisions for the crossover passages at all, but thats OK.