Cylinder head studs

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Scheffy.G

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May 11, 2007
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Does anyone know off the top of their head what the threadform is of the two front studs extending down from the cylinder head? I was tightening them down last night and apparently gave one a little too much snot and stripped it out. I'm just wondering if it's locally repairable (standard) or if it's a good excuse to send it off to CNW and get some other head work done (Whitworth).
 
It's a pretty common occurrence to have the studs pull out with less than specified torque. I replaced mine with 3/8" studs. 24 tpi on one end and 16 tpi on the other. That way you can use a commonly available 3/8-16 Helicoil. Of course, you have to replace the nuts with a suitable 3/8-24. I know this offends some Norton purists, but any time I can I replace the Whitworth fasteners with commonly available UNC or UNF fasteners. It's a lot easier to go to a hardware store to replace a fastener than wait for a supplier to send one, not to mention a lot more cost effective.
 
As I recall, the studs are 3/8-20 by 3/8-26. The problem with using 3/8-16 by 3/8-24, commonly available studs sizes in the US, is finding long 3/8-24 nuts to fit. You can make your own from hex bar stock in a lathe. You can also drill out the stock Norton nuts in a lathe, and install 3/8-24 inserts in their ends. An easier solution would be to hunt up Recoil brand inserts (Australian copy of Helicoil) in the proper size to repair the head. I know they are available in 3/8-26, because I've used them. I assume they are also available in 3/8-20, but don't know that for sure. It's worth checking. Putting inserts in the head is certainly the most straightforward solution.

Ken
 
Please keep original thread and nut size for next owners sake unless you make a big label.


Russ
 
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