I am rebuilding a 400 engine from 67' Firebird. My 400 historically ran hot and I experienced either fuel delivery or vapor lock problems as fuel combustion was inconsistent. I removed entire fuel system (including tank), cleaned it out, replaces hoses, etc. and rebuilt the carb.

Considering machining the plenum on my stock GM manifold, installing a thin heat dissipater plate and installing a 1" carburetor spacer (Hamburger or Mr. Gasket products) to improve air flow, dissipate heat and fuel combustion.

Has anyone machined the OEM GM manifold and added dissipater plate and/or spacer?