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MG MGB Technical - Thread Size???

Anybody know the thread size on the flexible hose for the oil pressure guage? It goes between the adaptor on the block and the male/male adaptor mounted by the pedal box. I want to put an adaptor in line to fit an oil pressure light. The fitting looks like it seals on a taper in the fitting.

Thanks,
Neil
Neil Lock

It's BSPP, I believe, and the adaptor is a stock part, fitted to cars with the anti-run-on valve, where the switch for the valve goes. Just put the pressure switch in there. It replaces the current coupler. If you have the AR valve, there are switches that will work the light and the AR valve.
FRM
FR Millmore

Hi Neil, if it's tapered it's probably 1/82 BSP
Ron
R. Algie

Should have read 1/8" BSP!
R. Algie

The threads are not tapered, the seating faces of the fittings are, which has nothing to do with the threads, and everything to do with making it work. Hence, the idea to use the part that the factory made to do the job.
FRM
FR Millmore

I've had the measuring gear out and it's 1/8" BSP Parallel with a conical seat providing the seal. Sorry, wasn't clear with the question, it was definitely not a taper thread. We didn't have anti run-on valves in the UK. Oil pressure switches are normally 1/8" NPT so I'll be able to get a tee piece now I know the thread size. Thanks for your comments.
Neil
Neil Lock

Neil-
Seems to me that Paul Hunt has spoken of anti run-on valves as OE on some cars over on your side. Your problem will be that you need the BSP/taper seat on two sides, and the 1/8NPT on the third. Sorry I have no reference for the part #
FRM
FR Millmore

Neil - The late MGBs in the US have the fitting you are looking for. It is a male - male - female that takes a pressure switch in the female section of the fitting. I Used one in our TD to give an audible alarm when oil pressure is lost (I hammered a couple of bearings because I didn't notice the oil pressure drop). I used the anti run on pressure switch, used in the later MGBs, but since that is a normally closed switch, I had to put a transistor circuit in line to convert the signal for the alarm. E-mail me and I can send you Moss part numbers and the circuit diagram if you like. Cheers - Dave
David DuBois

This thread was discussed between 16/03/2007 and 17/03/2007

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