I will check but I should have some 5/6" UNF Jet/K nuts, as all the nuts in the Judd engine in my Ralt single seater hill climb car were UNF Jet/K nuts or 12 point nuts. I use to have a large chest full of jet and bi-hex nuts and grade 8 aircraft bolts in all different sizes but various friends have raided it over the 25 years+ since I was forced to give up speed hill climbing, when old cervical spine injuries caught up with me trying to take corners at 3 to 4G loadings. I will go down to the garage and check. Many thanks for the info. I have a feeling that someone has put 1/2" AF nuts on my exhaust manifolds which may explain both why they are very difficult to keep tight and to get a tool on to them. If I take new 5/6" K nuts down with me, I may have to cut the old ones partially off with a carbide disc in my Dremel tool and then split with a cold chisel.

Wilson

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