While changing the water pump in my '68 F250 with a '75 Lincoln 460 one of the long 5/16" bolts at the top broke close to the block. Of course there's no way to get to it without taking the front cover off so I didn't. I installed a 3/8" heli coil in the cover and filled the hole with silicone. No leaks yet. This was done yesterday. Any better suggestions?

 

It may last but I would fix it right. If the bolt is close to a water port it could start leaking into the engine and you would never know it till it's too late. At the very least I'd get a light psi cap for it, 7 psi should hold it.