I did the same thing a few years ago. I had purchased a differential engine and it was suppose to run on 20 degree temperature different. Well it didn't so I place it on the stove to get more heat, bad mistake I hadn't realized the displaced was foam and melted. I had purchased it from scisupply.com and called and the owner sent me another. When I matched the two together they were different. The one that was on my engine had a slot Across one side of it, where the new one had a second layer to cover the slot. Yea, no wonder it wouldn't run.now it run with a cold PAC.
Don