I was at arm drop live in Memphis Friday. It had rained all week and the track was green so I let a few cars go ahead of me to down a little rubber.The routine was the same as always, 160 degrees, roll through the water, 2nd to 3rd for a 3 second burnout, roll in,stage,launch, it only had a 1.45 60 foot,ran a 6.63 @ 102 then I heard a pop and the front end dropped. I thought a ball joint broke so I just coasted on through the lights.Then I saw water coming up through the edge of the hood so I cut it off.The freeze plug behind the drivers side motor mount blew out. I think that is what saved me as the motor mount dispersed the water as it came out. The freeze plug is brass but is very shallow like a 1/8 shoulder.They were already installed in the block when I bought the car 4 years ago. I will be putting in the deep ones with a 1/4 inch shoulder. I am very thankful to have not hit the wall Any ideas what might have caused it to come out? Block flex or just the shallow shoulder combined with the narrow block shoulder or something else?