Thread size of domed cylinder head nuts


Does anyone know the thread size of the chrome domed cylinder head nuts of a 1938 2.5 litre SS engine, used to torque the cylinder head ?

Thanks, John

From memory 7/16"BSF You can buy new dome nuts , chromed ready to use from Worcester Classic Spares
And in the end it’s probably cheaper than trying to repair worn ones.
Often the flats are damaged either from over zealous chrome platers , or people in the past tightening them with a standard length socket instead of a deep socket. And this makes it less likely to get an accurate tension wrench setting

Been spending time on 3 1/2 litre`s lately have you Ed? 2 1/2 litre studs are 1/2" BSF.

Off topic but look what turned up whilst looking for something else !
Re your comment ( Rocking horse etc ) I now feel like the Bloke who found the
100,000 dollar gold nugget down your way awhile back.
A bit late , but thanks for the positive comment re wheel KOs

The press in the middle / squeeze at the edges cap fitted many a oildrum in day of yore.
Peter B

Rocking horse indeed, althouugh perhaps avery constipated rocking horse
I hadn’t seen a 6 terminal one of those
One could turn up another bakelite base but the cap is another thing. Co incidentally the place that services my S Type give away little tins of mints when you get the car back. Which have exactly the same method of closing the lid. Sadly a slightly different size.

Look for oil drums.