Forum

[Jamie G]

I'm so utterly peed off... Got the whole engine together, put the head on and went to torque it down and one of the head studs has stripped in the crankcase. It's on the drive side and the head bolt just keeps turning. I had the head back off and pulled the stud and it's ok - there was some metal swarf on the stud but the threads were fine so I am guessing the crankcase thread has stripped.

What are my options? I would hate to have to pull the whole thing apart and helicoil it but I can't see an alternative. I'm gutted. It's a '61 Bullet by the way, an original matching halves crankcase as well

[JOHNNY SINGLES]

That's a bugger. Best and easiest way is to use a low temp melt alloy rod and propane,
very easy to use, heat the hole up clean with a stainless steel brush or stainless wire wool, (kitchen scourer) melt the rod into the hole, whilst molten put the stud in, let it cool and then simply unscrew it, the thread will be as good as new.
http://www.youtube.com/watch?v=843jjv58BCA

[simon]

Interesting vid. I've got some of the low melting point aluminium alloy rod but haven't had much luck making it work. For me with nice original cases I'd suggest you do,the proper job and strip it back. I'm not personally a fan of helicoils but they would certainly be the quickest solution other than Johnny's one. I personally prefer a threaded insert. This means tapping the stripped hole out to 7/16 or 15/32" and screwing in a loctited sleeve that you can then re tap to 3/8". Remember to pack the flutes of any tap or drill with grease so you don't loose swarf into the cases. I'd usually use a brass insert but if you want to make an invisible repair you could use aluminium.

[PeteF]

Yes, threaded insert is the way to go. You'll need the barrel off but you can do the rest in situ. A jig to keep the drill square-on would be sensible and watch out the swarf doesn't drop into the case. While you're doing it I'd do them all.

[Jamie G]

Thanks for that. Two questions: am I right in saying the studs are 5/16" cycle thread, and are the head studs prone to doing it?

[JOHNNY SINGLES]

Simon, The main reason people have trouble with this is it is very important to clean the alloy when you have started to heat it up and you can only use a stainless steel wire brush to remove the oxidation prier to melting the rod onto the item you are welding too.If you just use any old wire brush it will not work. This is the best way of repairing a thread in alloy, fitting a insert may weaken the remaining wall that is left.

[Norm]

Possible stripped the nut, I have had that happen a couple of times because the studs were a bit too short, drilled down through the head a bit deeper and new new nuts and problem solved

[Phil Ashbrook]

If I were you I would helicoil it , I had to do it to my short barrel stud thread and all my rocker cover threads and all my rocker bearing stud threads as I was stripping down the engine too many times , I'm gonna vapour blast the crank cases while I wait for the 612 crank to arrive by mail .

[Midge]

The alloy braze is ok on smaller items, but on an assembled crakcase it will take an almighty amount of heat. Propane won't do it and I doubt Mapp will either. Even if it does, the heat will likely damage bearings, gaskets and carbonise oil on the surfaces.

[simon]

Yes thought it might be a cleanliness issue Johnny. Oh are they 5/16" (been a while since I looked) then a 3/8 insert will do the job. No issue with strength as there is tons of meat in the case. Not sure I'd replace ones that are ok though. I had a 51 Bullet that had never stripped. If they last 60 plus years they must be basically ok.