The cylinder heads of Type-1 and Type-4 engines tend to get pretty hot. That's why you don't have to pre-heat the manifolds on dual carb motors.

Dual carb engines often have problems with vapor locks due to heat up on the carburettors.

You can avoid this by using heat insulation flanges which isolate the carbs from the manifolds.

One set is for one throttle and comes with paper gaskets