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[PO51UHD]

Hello All

Just putting Connie the ‘59 Constellation’s top end back together and one of the head nuts (the long ones) won’t tighten up when torquing...
I guess I’m into stripping that side down again. From your experiences, which is most likely to have stripped: head nut, stud or crankcase?
Assuming crankcase I assume it’s a Helicoil job...?
Any good tips most welcome; thanks in advance!

[singleminded]

I sympathise! It's a sickening feeling when that happens.

However, is there any point in second-guessing what is the most likely problem and what remedial action may be necessary?
It appears from what you say that you just have to start stripping it down. When you find the problem, let us know. I'm sure that you will get lots of helpful suggestions.

Good luck!

[stinkwheel]

It's been the crankcase when it's happened on my bullets. They are pretty straightforward to fit an insert to. If you use a well greased drillbit and tap, appropriate stuffing of openings with rags and go slowly, you can catch all the swarf and do it in-situ.

[Marko]

It was the crankcase stud threads that stripped on my Connie. 1st time I fixed it I used a helicoil but did a cock up, it was much too short (though i did buy it from H's & did tell the chap on the phone what it was for) .. anyway i ended up having an insert made at a local engineering shop & since then its been fine . There was someone on here a few years ago who sent me some info on the mods he did to his Connie (sorry cant remember the name) & what he did was have some new "stepped" studs made (3/8 threaded into case, the rest 5/16 as standard)

[TomCraig]

My bet, from experience, is pulled case thread easily repaired with heli-coil. Maybe you will be lucky and its one of the others.

[PO51UHD]

Thanks for the replies!
I ordered a Recoil kit from MrH and drilled/tapped the thread hole. Unfortunately the Recoil kit only contained short (1.5D) inserts so paying heed to the advice here I didn’t use these and so I’ve ordered a few 2D inserts. I had assumed the kit would come with a mix of short & long ones!
My main concern at drilling/tapping was keeping the new hole perpendicular to the casing, so I made up a Heath Robinson jig using a piece of scrap Ally and a couple of short Ally tubes to pick up on adjacent stud positions. The blue tape is packing because the stud threads are rolled, the shank is smaller in diameter than the threads

[vince]

Hi, I use a small V block to get the drill straight , aligning the drill down the v. Vince

[RocketRR]

If this doesn't work a good trick is to use a T20 Triumph Tiger Cub stud as it has a wider diameter bottom thread than stud diameter. This meaning you get a stronger new thread in the bottom and same stud diameter. Did this on my Connie on the advise from an old Gander and Grey employee in Bristol and it never failed again in my ownership.