A friend and I replaced my battery and starter in Methuselah - my '86 F150 Lariat with a 302. The bottom bolt was missing. My friend went to store and match up the bolt (but forgot to note the size) - the top bolt tightened up nicely, but the bottom bolt would slip while tightening. My friend was able to finger tighten the bolt, but even a slight torque on the bottom bolt would cause it to slip. Any clue as to how to fix? A friend suggested a Helicoil... but they are expensive. Anyone else had this problem?? Thanks.

 

It does sound like it's stripped out. You might be able to run a thread restorer through it before the helicoil.

 

Chances are you need to helicoil it. Or just leave it. It went how long like this already?