[SLESTAK75]

The only way for a valve to come in contact with the piston is if its open when the piston comes up. Most likely this is timing related. Pull your plug and hold a straw into the cylinder. Turn the flywheel until the straw indicates the piston is at the top. Then check the position of the cam. The two smaller marks on the cam should be even with the top edge of the head (let me know if you need me to draw a crude picture). The only other reason the valve would touch is if it is sticking open. Also take the time now to check the valve lash. Ckau explained a good method of this in another thread. Ill post the thread in a second.