Stripped Stud Quandry

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Tangozulu

Tangozulu

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Reinstalling my beautifully prepped, rebuilt, vapor-blasted cylinder head on my '71 Commando. As I torqued the bolts/nuts in proper sequence to the correct specs using my high-tech digital torque wrench, when I got to the long chrome nut on the left front downward facing stud (#7 on your torque-sequence chart), approaching 300 inch pounds, it suddenly got soft. Next crank couldn't reach 200. I've been here before with that sickening feeling, the stud stripping/pulling out. So, I figure I have two choices: 1) trust the other 11 bolts/nuts and leave it alone and see if it all "works" OK, or 2) take it all apart again and repair it. And if I choose option 2, where would I find the proper BSF? Whitworth? helicoil to do it? Or? OK guys, what say you?
 
Been there. Take the head of and repair both of them, you could use any thread you want if you can make the studs.

Dave
 
On a '71, the threads will probably be BSF. I'd suggest taking the stud out and measuring diameter and TPI. There are lots of engieering documets that would identify the thread. My go-to for all that kind of stuff is an older copy of Machinery's Handbook. Drop me a PM with the measurementsand I'll look it up, if you like.

For something as small and light as a Helicoil, one of our UK members could send you one. You might be lucky enough to find a Helicoil source more locally that carries the British thread stuff.
 
frankdamp said:
On a '71, the threads will probably be BSF. I'd suggest taking the stud out and measuring diameter and TPI.
Click to expand...

The thread is BSF.
 
Search the forum for lots of info on this repair. I think it comes down to three basic choices.

1. Use a BSF 3/8-20 helical insert and the stock stud. The Recoil brand kit is easily available in the US.

2. Use a 3/8-16/3/8-24 automotive stud, or make your own, and fit either a Helicoil style insert or a heavier duty fully threaded insert, like Timesert, key locking, etc.

3. Send it to Jim Comstock for custom bronze inserts and studs.

In any case, good idea to do both while you're at it.

There are other options, like drilling out and tapping for a custom stud with larger thread on the head end, but you don't see them used much. Option 1 is the simplest, but option 2 (with a solid insert) or option 3 give you more strength.

Ken
 
You could do worse than treat yourself to the cNw head fixing kit, should be easy to get a local engineering firm to fit the required 3/8 x 16 insert.

The 12 point fixings certainly aid easy torquing with sockets rather than iffy box spanners!
 
why not leave it be, do nothing?

good chance all them other damn bolts will be enough to keep things in place

I know, blasphemy but so what, ride it, no one else will know that one bolt is not perfectly torqued if you don't tell em, but now you told everyone....
 
1up3down said:
Why not leave it be, do nothing?.... Good chance all them other damn bolts will be enough to keep things in place....... I know, blasphemy but so what, ride it, no one else will know that one bolt is not perfectly torqued if you don't tell em, but now you told everyone....
Click to expand...
Well TZ I would be tempted to try it out since it is all together, shoot if it leaks then you can go down the road of repairing it, and if you have to repair it I would send it to Jim (Comstock) in Pueblo, CO. for his inserts and I would follow Nigel's advice and get the cNw stud kit too----again that's if it leaks or when-----you might get a season or two before it goes. Cj
 
lcrken said:
http://www.amazon.com/Recoil-Insert-Kit-Bsf-Inserts/dp/B004W6CGP0
Click to expand...

Woo-Hoo! There it is. Mucho Gracias

Actually, I'm inclined to risk it, and have the Recoil kit in reserve (not that expensive). What I like about these Brit bikes is I can jerk the head off w/o much hassle. When I repaired a head gasket leak on my 1970 Yamaha XS-1, I had to remove the engine from the frame to get the head off and that lump was a two-person operation.

Speaking of torquing, I trust all of you know about the Motion Pro torque wrench adapter that makes it possible to torque all those open/box-wrench-only nuts.
 
JFWIW, I've had a niggling oil drool from the front left, I figured a head gasket job in the winter. Then I found that stud loose, nipped it up, oil leak is gone. Soooooo..... I'd wager that it WILL leak. Sorry. :roll:
 
DEfiining moment in our mechanical career

I you are a purest, then do the BSF repair, otherwise the smart money is to get the CNW kit or send it to Jim.

BSF is dead and if I was in your shows i would use the opportunity to exocise the BSF demon in total when the opportunity arrives.
 
Because the stripped threads are in the head and not the case, I would be inclined to try the helicoil myself first. (even though I hate using helicoils, I supose they do work without issues sometimes...) If the helicoil doesn't work, I would take the head to robert seymour, who's a machinist in tukwilla, and have him install a timecert I don't know if he's still around, because it's been a while since I've needed his services, but he's a retired machinist from boeing and there isn't much he can't fix. His nickname is "the great seymour" if that tells you anything... It's nice to have these kind of guys nearby. He's probably in the tukwilla phone book if you need him....
 
After sleeping on it and waffling like a politician pandering for votes, I decided to order the recoil BSF kit and fix the damn thing.
 
Tangozulu said:
After sleeping on it and waffling like a politician pandering for votes, I decided to order the recoil BSF kit and fix the damn thing.
Click to expand...

Good call. :)
 
One of my helicoil thread repairs is pulling out. I'm thinking I'm going to install a Timesert.
 
Tangozulu said:
After sleeping on it and waffling like a politician pandering for votes, I decided to order the recoil BSF kit and fix the damn thing.
Click to expand...
A recoil kit is no fix in my opinion, only a bandaid when there is no other option. A nice beefy coarse threaded insert on the other hand, will make it stronger than new. If you want to kick it up a notch, do all available or applicable threads. You'll never have to worry about pulled studs again.
 
Try these: http://www.acmeindustrial.com/keylockinsert.htm The "keys" are driven down into the cut threads in the head locking it into place. They work very well and won't come loose. I'm not a machinist and did two heads in my garage using my drill press. I used the key lock inserts along with the CNW repair kit. I'm very happy with the results. I'm confident now that those three studs won't pull out.
 
Are you sure that the. Thread has not stripped in the long nut rather than on the stud? I would first try a new nut and see how you get on.
 
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