burg650 said:
NormanB making new threads probably the best thing to get a tight fit with a new bolt but my concern would be while tapping the hole would it not cause shavings off the metal to get in the case. If this happen how would you flush out the case to make sure none is left inside before you fill and start running again, can just see little fragments of metal mixing with the oil and start going all around inside the case.
Whichever!
If you tap to existing size you are going to create shavings.
If you helicoil you are going to create shavings.
The 100% solution is to do it on the bench either way.
The 99% solution is to use heavy grease to trap the shavings.
In the event the shavings fall inside the gearcase they are soft aluminium - my guess is they would sink to the bottom and draining the oil would carry most out, any that that remain are likely to be harmless to the gearing - but that's just my opinion.
FWIW when I recently sheared a valve cover bolt, I drilled and used an eazi out using strategically placed cloth and heavy grease to catch the debris.