I've read a lot of interesting threads about little things like hardware and grease cups, I can't recall one about petcocks. They all look the same at a glance but they aren't. I got these 2 along with a bunch of stuff this morning. The one on the left has "BB" stamped in the handle, the one on the left "U". The bodies are a little different. I'll just guess different suppliers, but maybe at different times or all at the same time? Any information?
I would suspect they are either for different years or one is not for a T. The threads look different. All the ones I have seen for a T have pipe threads on them. The one on the left looks like a different type of thread.
I didn't notice the thread. It was screwed in the bottom of an NH carburetor instead of the usual T-handle drain.
The Model A and AA used them on the drain on the water tube. They are stamped A, AA, B AND BB. They work and fit the same as the T ones.
The early ones did not have a spring and split pin. They have a screw in metal thread and a special washer. Having no tension on the taper allows worn taps to vibrate open, and you can loose a lot of oil. The spring loaded version is a good improvement, and likely to be cheaper to make.
Allan from down under.