Make sure you have a good cooling system and there are no air pockets. If you have access to an Air Lift coolant filling system use it because it will also show coolant leaks. If you are breaking in a new flat cam follow the cam grinders recommendations to the letter for success. The card that came with my Howards cam had a procedure that is a little different than I'm used to. It was a few 10 minute intervals instead of the usual 20 minute straight deal which I prefer because you time to check things as you go.

Gus