Manifold heat cross over physics and benifits

Manifold carb heat is like most things, way too much or too little creates problems. Adding ethanol seems to reduce the vapor pressure of fuel, so older designs are too much heat for todays gasoline. Heat risers were designed as a means of heat control, however conduction adds heat, as well as the control of exhaust.

As others suggest port EFI is the solution.

An air cooled engine with remote carb will ice internally, in humid weather near 32 Fdegrees. The same engine with EFI runs without problem.