Need a little help with a thread insert problem. I have a GM V6 in my boat and the thermostat housing is bolted to the water manifold with two 3/8 x 4" bolts. The boat is 20+ years old and the bolts and holes have rusted such that there are no threads left.

I installed a helicoil insert and it seemed to work ok, however, long story short, I needed to remove the bolts to replace the thermostat and the insert backed out with the bolt, destroying itself in the process.

Since opening this area is part of my routine winterization, I'd prefer to not have to install a new helicoil each time. Is there a way to keep this from happening?

TIA

This may be a dumb idea, but you might try tack welding the insert into place.

What about boring it and tapping it to a larger size?

I thought about maybe trying to stake it in place if that makes sense. Maybe staking would be an option with a sleeve insert (timesert) over a wire insert?

I thought to bore to 7/16. Could be done, I think, but would be a pretty big job for me (hand drill) as the thermostat housing is a solid 3" piece I would have to drill through. I do like the idea though because it would be solved (for another 20 years ;-)).

[This message has been edited by njw92 (edited 4/9/2012 3:06p).]

http://www.timesert.com/

/EOT.

yep, helicoils have no place on an engine. Timesert is the only way to go. They will have their own roll-lock mechanism, and a bit of green loc-tite is always a good idea.

Is this cast iron you have to drill through?
That should be pretty easy with the high carbon content. You won't even need any cutting oil.