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Whilst screwing the cam cover back on my car after a head gasket change i managed to snap the head off of one of the bolts holding the cam cover on. The screw body is well and truly stuck in the hole and i was wondering if you guys had any ideas on how to get it out or if just having the left and middle retaining screws would be enough to stop it leaking oil around the cover gasket.

A friend at work has a screw tool for just this which has a reverse thread whihc you screw through the centre of the broken screw and once it bites as you screw further it undoes the one in the hole. Problem is he reckons i'll need a 2mm hole to get it going and the snapped screw itself isnt much bigger. We'll see how it goes tho.

If this fails other ideas apart from drilling it out (how difficult is this to do and not ruin the thread) are to weld a nut onto the top of the broken screw to provide another thread which i can screw a bolt into. Or as i just said seal the third bolt hole up and just rely on 2 bolts and hope it doesnt leak.

What do you reckon?

As your mate says, stud extractors is what you need. You can get really small ones, so you shouldn't have a problem extracting it.

Failing that, you could just replace the bearing cap that the bolt has sheared on.

Drilling out is a fine art, and the block isn't the best place to practice it.

or the head