Morris Minor Owners Club

Well done Richard! It's not something I have ever messed about with - never had any stripped threads/cracked nuts (ouch!) - just swapped complete assemblies around. Borrow a nut from the other set meantime !
Edit - looking at Minispares website -the rocker adjusters are listed as being 5/16" as I suspected..... and nuts are 16p each.
http://www.minispares.com/shop/classic/ ... .aspx?1004

I personally would not use the M7 nut as the angle of the thread is 60 degrees opposed to 55 degrees on a British thread.
While this statement may seem a bit odd in that both nuts fit, the thread angle of the metric tread when tightened will be more prone to stripping if overtightened due to how much contact the nut makes with the thread.
On fine threads it will make a differnce.

Richard

angle of the thread is 60 degrees opposed to 55 degrees on a British thread

As it's part of the engine, I would think that the thread form is UNF, which also has a 60° thread angle.

Thanks for finding the answer. I suppose on reflection 7mm would be out of keeping. Although you could say the same about 9/32''!