AL would be the worst material: It has the best heat transfer (thats bad). Phenolic/bakelite/wood would be a better insulator. They use AL because its strong and easy to cast.
Sorry, I've been away from the car for a while.
I assumed the bakelite was used for cost, and wooden would be made from expensive hardwood. Is it okay to use stacked 1/4'' gaskets? They are fairly stiff and have some compression in them.
