While my heads are off, Stage V iron, I’m wondering if it worth filling the crossovers in the exhaust ports. I know it was done a lot in the past. Is it effective? Anyone ever test it?

Thanks
Bill

Stuff 'em with tin foil. If you don't like it you can remove it. But if your manifold doesn't have the crossover then there is no point in doing anything with the heads.

Just use the Felpro valley pan with blocked crossover ports. That’s what most people have been doing for 30 years.

M/P STAGE 5 wedge filled in from factory

Not the later ones. Or I wouldn’t be asking.
This is about cleaning up the bowl area, not just blocking the flow through the intake.

I've seen many BB and SB iron heads, before the new aluminum heads came without that passage , blocked off on the inside of the exhaust ports with a piece of thein steel brazed over it
I've also tried stuffing them full of stainless steel wool pot cleaners with out success, they would blow out through the exhaust quickly