[blykins]

Well I guess since the valve was not opening, it couldn't have smacked the piston...but I'd say there are other problems present. Which valve was it? Intake or exhaust? If your exhaust valve wasn't opening, then I wonder where all the spent gases were going? If your intake valve wasn't opening, then more than likely there wasn't anything to combust...you just had a dead cylinder. Was it missing? Running rough?

I really don't know what the banging could have been though if the valve wasn't smacking a piston...