Hmm Alum bolted to the top of an engine & heat rises , can you say heat sink !! Blocking the heat crossovers & using spacer for the carb helps , but a composite intake would be good . I drove a car on the highway below freezing for an hour or so ,I had the air cleaner sealed to a SS hood scoop , it started to run badly so I pulled over & popped the hood , we had the heat crossover blocked & the carb & Intake were ice cold , the fuel would not atomize !!