I have a 1984 3.7 mercruiser. I stripped the threads from block while torqueing the head (new gasket). So I drilled
and tapped a new heli coil into the block. I had asked a local machinest if I should install 2 sets of the coil into the threaded hole but he said it wasn't needed. I torqued the head down in 3 stages to 130 ft. lbs.(found the info on that on this web site).
The re-worked threads held and felt just like the rest. Started the engine and warmed it up to operating temp. A few days later I took the valve cover off to re-torque and that same bolt didn't hold. It's at 90
ft. lbs. and I can turn it just enough to tell its not getting tighter. Will this hold up for a season? If not how can it be
repaired again. Also is there a way to repair this without removing the head. The stripped bolt is on exaust side and the
first one toward front of engine. Thanks for your advice.