I was diagnosing a valve cover gasket oil leak that's been there since I bought my 164, and decided to re-torque the valve cover as a stop gap to buying anew gasket. Two of the bolts just spun and wouldn't torque down, including one bolt on the front where the leak is coming from, where the dipstick attaches. I assume the PO stripped the threads in the head (it's aluminum, right?) and introduced the leak since there isn't a good seal w/ the head. So what are my options here? I'm hoping this isn't a "pull the head and send it to the machine shop" solution. This is on a 12V motor, if it matters.