Yikes! Have you ever looked at these Fasteners closely?
I’m not sure how many I’ve looked at but far more than most people I’d imagine. Rajkot makes a pretty crude Nut, last ones I was looking at had threads pulled and a quarter of a thread tore loose and hanging out of the bottom of one of them. You guessed it, making this nut close to right would take a few more machine steps, and it’s also possible that some who make them don’t know that a simple chamfer could protect the threads from pulling.
My Advice is to look at these head stud nuts closely, if they’re really bad, you’ll Find that there are nuts at the hardware store that match the threads per inch, and the size as closely as the originals do. I chamfer the bottoms, and I use a belt sander to round the edge all the way around the bottom, so the sharp edge doesn’t dig into the head and give a false torque reading. I sometimes find the bottom side so rough and ugly, I clean it up on the belt sander as well.
Once I’ve done this, I rub an anti seize into the bottoms, and I coat the head studs with same and wipe off the excess. After I clean up the head surface, and the top of the block, I check the cylinder liner for the proper protrusion above the deck (often .010″) I place a new head gasket put 30 WT lube oil on the nuts, and incrementally go around with a cresent wrench and get things fairly tight before I grab my torque wrench and set it for 140 Foot pounds. I like to run the machine at full load 2800-3000 watts at sea level until the engine is soaked warm. Allow the engine to cool over night and retorque to 140 foot pounds again.
If you look at the galling on the bottom of some of the head nuts, it’s easy to believe that whatever the the last guy saw on the torque wrench (if ever used) was way off. Breaking those extremely sharp edges is going to make a world of difference. We all hear about leaking head gaskets, I do believe following these steps will eliminate one source of trouble.