This pipe fits later XK-140 (from engine G.1908Z) and all XK-150 provided they have been fitted with a 4.2-liter oil pump. (This part will not fit XK-120 or early XK-140 with the gear-type oil pump.)
Original 3.4- and 3.8-liter oil pumps had 3/4" oil suction and delivery ports and associated pipes. A new, higher-capacity, oil pump was fitted to 4.2-liter engines with a 7/8" suction port and associated pipe. (The pressure, or delivery, port and pipe remained at 3/4".) Soon, all replacement oil pumps were of the later type and a sleeve was fitted to account for the difference in port sizes. While perfectly functional, it negated the benefits of the larger port and pipe.
Which brings us to this big-bore pipe. When fitted to a 4.2-liter oil pump, it guarantees the full benefit of the high-capacity pump. And, the design is superior to the factory version fitted to 4.2-liter cars and offers superior oil flow.