Buy another engine.
Buy another engine.
Bah. forget that noise, a Helicoil ain't rocket surgery. So long as you have a drill with enough cojones, a 12mm Helicoil is no more difficult to insert than a 5mm one (where do you find 3mm Helicoils? I needed to mail-order 5mm ones to repair a rack mount hole in the rear dropout of my bicycle...) Remember, a drill bit self centers to an existing hole, so as long as the threads stripped cleanly and evenly, your only real concern is getting the Helicoil all the way in. (since I'm assuming that this is a blind hole, and you really don't want to drill it any deeper than it already is, for fear of breaking through to a water or oil passage, you may need to take the Helicoil tap and after tapping until it hits the bottom of the hole then cut the end off with a cutting wheel to make a "bottom tap" and then have another go at it. In an emergency when the only Helicoil I had was too long and I'd already inserted it in the hole, I have dressed the end of it with a flat file, but I would be hesitant to do that on a head bolt. I would carefully measure depth first, then modify the Helicoil as necessary before inserting. I seriously doubt that you will have THAT problem, however.)
I would, however, replace at least that one bolt, and check with someone familiar with your engine if a Helicoil can successfully be inserted in that particular hole. Sometimes there just isn't enough meat in that area of the block so that inserting a Helicoil will significantly thin the structural metal in that area - in that case the solution is usually a Timesert. (I know that the Timesert is the preferred solution for pulled head studs on a Porsche flat-six; I assume that it is for this reason.)
I would of course use a good straightedge and feeler gauge to check for warpage/unevenness of both the block and head surfaces before calling it soup and reassembling.
nate
concur. /much/ cheaper.
Forgot to mention... when checking block with a straight edge, you may discover high spots immediately around the bolt holes. You'll want to knock those down by chamfering with a larger drill bit, and/or with a flat file if they'd require a huge chamfer (but chamfer would be preferred)
nate
Time-sert and Helicoil require virtually the same amouint of space - but the 'sert makes a nicer job.
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