Can gain a little cooling by blocking the heat passage in the intake manifold.
Gaskets to block it once were available but we just cut and inserted a steel shim between the gasket and head.My usual source was antifreeze can bottoms but just try to find one of those today.I think a piece cut from a section of vent or heat ducting would be about right.Never need manifold heat in Tennessee or 'Bama but be aware the dual exhaust will now sound "different"at low speeds, somewhat louder,the pulsation sound will be more evident--like you can distinguish pulsations one side from the other.
The first one of these we did we worked halfa day to prove to the owner it wasn't missing--the sound change had him fooled and us too.
Factory fuel injection had no need for manifold heat right up to the last SBC so the sound difference can be related to any of those with duals.
Hotrod Lincoln will remember the old flathead Ford trick they referred to as pitting pennies in the manifold.Actually in the gasket I think to block the heat.
