1965 B40F carb stud threads ? BSF CEI UNF ??

[hoogerbooger]

I ask as the Amal site tells me to use nyloc nuts with my Mk1 concentric... so I need to buy these.

On a web search I'm getting conflicting info on the thread.  I've tested with some other 5/16 bsf nuts I have it wouldn't appear to be a bsf thread.

Anyone know what it ought to be for a 1965 B40f ?

[JulianS]

Should be 5/16 x 26tpi cycle.