If one wanted to block the passages in the manifold to keep the heat out of the manifold what would be a good way to do it?

 

Stainless steel shim stock at the intake gasket
filler material like zinc in the heads
Solid cast iron plugs which are hard to secure to not rattle

 

Stainless shim stock won't burn thru?

 

And for aluminum intakes, aluminum plates welded into the port openings.

 

I had a stainless shim stock added to my small block 2 years ago, still working great.
Before I added it, we could see the aluminum manifold turning a brownish color, now no color change.
Frank

 

Nothing lasts forever. I have some 0.005" shim stock I used a long time ago but not my car so not sure how it lasted.
Anybody wish to try it and report back with results I can drop a couple pcs in the mail.

I would think 0.010-0.020 material used with a thick composition gasket would not interfere with sealing and SS in general is pretty tolerant of heat abuse.