As part of my engine recondition, I decided to save money by reusing the old head studs. To my regret, I used a recently purchased die nut to clean up the threads on the upper end of the studs. The die nut was very tight on the threads and took off a significant amount of metal. After doing a few studs, I tried the nuts on the studs and found that they were very loose, and didn't use the die nut on the remaining studs.
When tightening the nuts with the head in place, one of the loose nuts sheared it's thread at a torque of 10 lb-ft. Trying a second nut on that stud gave the same result. The nuts on other studs that had been cleaned with the die nut felt dodgy at about 15 lb-ft. The nuts on the other studs tightened satisfactorily to 20 lb-ft.
Was I using the correct die nut? The nut has the inscription 5/16 BSF. The Cornwall Austin Seven Club publish a list of thread types saying that cylinder head studs have BSF threads.
Is the answer - the die nut was made incorrectly?
25-06-2023, 09:11 AM (This post was last modified: 25-06-2023, 09:13 AM by Speedex750.)
Hi Graham,
You do have the right size, but die nuts tend to take off a deeper cut that the original. Better to use a split die and adjust it until it is just cleaning the thread without cutting. I hope you can extract the broken ones without having to lift the head and disturb the gasket. Make sure you use a sealant on the threads to help keep the coolant in!
If I am to reuse studs, bolts etc, I clean them up on a rotary wire brush. It’s amazing how much easier it is to get the nuts on, or to screw them into their threads. I do have a set of dienuts, but only use them when their is no other alternative.
Die nuts are not generally the best idea on on a used stud particularly if there has been any stretch in the thread through use. As Dave suggests split dies are a better option but again if the thread has stretched replace the stud and always use the best quality you can find.
Thanks for all the advice. I never expected that die nuts would be made so inaccurately. This one is going in the bin.
It was false economy to reuse old studs after spending on rebore, new pistons, valves, etc.
I hope this thread is seen by others contemplating use of die nuts.
Cheers
Graham
It was false economy to reuse old studs after spending on rebore, new pistons, valves, etc.
I was going to say nowt, but since you have now said it, I can only wholeheartedly agree! This is not 1964, and we are not wrestling with Hillmans or odd Standards. Good quality replacement items are what makes Seven ownership so rewarding.
