PART NO.  SPL.PAGE  DESCRIPTION                                                           
11G15     15.A.8    Union -oil pressure gauge pipe, engine unit, 1500) -changed to AAA628
11G15     16.A.8    Union -oil pressure -(gauge pipe, engine unit, 1600)
11G15     16.A.29   Union -oil pressure -(gauge pipe, engine unit, 1622)

11G15 Connector -oil gauge pipe -(instruments, 1500, 1600, 1600-MK-II) engine block to flex pipe -(changed to AAA628 for later models)

Alternate numbers:
BMC: AAA628
Moss part number 460-015

Use with seal washer 6K638

Mating thread for these parts is 1/8-BSP (28 threads per inch) The replacement hose from Moss Motors and Limora was reported to be faulty in October/November 2021, having incorrect thread that would not connect to the male threads on the mating fittings.

Note this union may have a fairly small center through hole that serves as a restrictor orifice to damp out hydraulic pulses that might make the gauge indicator needle vibrate. Not sure if the size of this hole matters, as I have never seen any vibration on the oil pressure gauge. But the gauge action may have slow response on engine start-up if the signal line has air in it. It is a good idea to bleed the oil signal pipe at back of the gauge to remove trapped air any time after the connector hose has been disconnected.