Hey Guys

My top piston blew on my last race meeting. When i got home home after a miserable day, i decided to have a look and see how the piston looks. First i had a look at my bottom piston and found that it was looking as good as new. Next i went on to have a look at my top piston.... What i found was a piston and the head full of pen-point size holes around the radius of both, but my barrel didn't have a single scratch on them and the piston ring was still in tach.
I knew my gasket was blowing in the race as the overflow bottle was full of water, but the temp was still at 70 just before it popped.

Could it be that water got in the head and made so much damage? Secondly, how important is it to use a torque wrench when putting on the heads(Can over tightning cause the gasket to blow????)

Thx a thousand!