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 carburettors. You can avoid this by using heat insulation flanges which isolate the carbs from the manifolds. The also needed paper gaskets are individually available, so you can re-use the insulation flanges.

The flanges are for Weber 40 IDF and 40 IDA and also Dellorto 40 DRLA carbs . One set is for one throttle and comes with paper gaskets.