Coolant leak -hydro locked engine

Went to run in the Gamblers Race last Wednesday night, after I rolled the car out of the trailer I hit the starter button and nothing , then I see water coming out the drives side header.
I am taking the heads to local machine shop to have them pressure tested, I cannot see any crack. These are W-2 early design heads.
Anybody have a idea ? Are these heads prone to cracking? Hottest the engine ever got was 200 degrees The head gasket is intact.