David, good point. The pressure occured with the battery system disconnected. Ran the motor to operating temperature on a saturday for about 3-5 minutes. Shut down and disconnected battery system. On sunday the cooling system still had pressure. I bled the air. On Tuesday the system had pressure. Bled again. On Thursday the system was FULL of pressure again. Drained system.

What kind of damage do you think this caused to my aluminum heads?