Although I have been able to offer a 'generic' 1/4" BSP 'straight through' breather for some time (with hex to fit modern AF spanner sizes), I am now able to offer the proper and correct brass one way breather valve, as fitted to all SOHC (and DOHC) crankcases behind the drive side mainshaft casting. This special valve is almost always badly chewed on original engines and is now almost impossible to find. They were also fitted originally in bare brass, as shown. This version, like most items I am reproducing, has been manufactured to be indistinguishable to the original, and as normal in this case an original was used as the pattern. The outer breather union is machined to the same Whitworth spanner hex as the original, is plain brass as per the original, and has the same thru-hole size as original. It is threaded internally to take a small screw in insert, which retains a small ball bearing (in stainless, to prevent corrosion), which provides the one-way breather mechanism.