I was tightening my valve cover bolts when one of them broke, leaving the broken piece inside. Is is ok if i just leave it alone? Its the bolt on the front left corner. Or is it better to have it removed by a machine shop & replace the bolt? That means I have to have the valve cover removed 1st before they can drill & remove the broken bolt, right? Or can they just try to drill the broken bolt w/out removing the valve cover? pls help!!