Retorquing the cylinder head?

Dances with Shrapnel said:

I like your Aluminum Bronze inserts for threads. What lead you to that?

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Dances with Shrapnel said:

Thanks Jim.

I know I may be asking the obvious but for the benefit of the listees, what lead you to using the inserts?

By the way, Holmeslice is awstruck with the head gasket. Should see rumblings on the list in a few weeks - dyno time but probably after Barber.

Did I read you were heading to Barber?

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Dances with Shrapnel said:

Thanks Jim.

I know I may be asking the obvious but for the benefit of the listees, what lead you to using the inserts?

I had to do a similar repair to my Weslake head about 20 years ago ( and more recently) - the head gets soft eventually and the 5/16 unf helicoils fitted under the exhaust ports pull out. Once a helicoil pulls out you're buggered and a more complex fix is required - hence the bronze insert.
In my case I think the idea came from Phil Irving's Tuning for Speed - he mentions using bronze inserts in repairing crankcase stud holes.
For those that haven't come across it before I would really recommend Tuning for Speed even if you not going to be doing any tuning as such. Its title is a bit of a misnomer as it covers a lot of refurbishment, measuring and blueprinting techniques directly applicable to the technology ( or lack thereof) in Norton twins.
The bronze inserts are quite easy to make - if you can get some stock the right OD you could possible get away without using a lathe. In my case I die cut the outer thread 7/16unc, leaving it slightly oversize and then drilled and tapped for the original 5/16 unf. I sunk them just below the surface and then whacked the edge of the hole in a couple of places to peen them in. I also used a high strength loctite but I don't think any loctite would survive the temperatures in that location.

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SeeleyWeslake said:

Dances with Shrapnel said:

Thanks Jim.

I know I may be asking the obvious but for the benefit of the listees, what lead you to using the inserts?

Click to expand...

I had to do a similar repair to my Weslake head about 20 years ago ( and more recently) - the head gets soft eventually and the 5/16 unf helicoils fitted under the exhaust ports pull out. Once a helicoil pulls out you're buggered and a more complex fix is required - hence the bronze insert.
In my case I think the idea came from Phil Irving's Tuning for Speed - he mentions using bronze inserts in repairing crankcase stud holes.
For those that haven't come across it before I would really recommend Tuning for Speed even if you not going to be doing any tuning as such. Its title is a bit of a misnomer as it covers a lot of refurbishment, measuring and blueprinting techniques directly applicable to the technology ( or lack thereof) in Norton twins.
The bronze inserts are quite easy to make - if you can get some stock the right OD you could possible get away without using a lathe. In my case I die cut the outer thread 7/16unc, leaving it slightly oversize and then drilled and tapped for the original 5/16 unf. I sunk them just below the surface and then whacked the edge of the hole in a couple of places to peen them in. I also used a high strength loctite but I don't think any loctite would survive the temperatures in that location.

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Dances with Shrapnel said:

SeeleyWeslake said:

Dances with Shrapnel said:

Thanks Jim.

As to my original question "what lead you to using the inserts?", in your case it sounds like cylinder head softening up from heat leading to thread pull out. In my opinion it could also be an inadequate design of thread pitch, diameter and/or depth of thread for the specific application.

In general I am wondering (out loud) if significant over torquing can be a contributing factor?

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