Oil line fitting 4ADT

[bitsobrits]

Can someone tell me the thread size/type of the fitting that screws into to block above the oil filter adapter? It appears to be about 1/2" straight thread, about 14 threads/inch, which must be Whitworth? My car is missing this part.

[bitsobrits]

Okay so here I am responding to my own post again! The thread on my block for the oil line fitting turns out to be 1/2" Whitworth. I purchased a 1/2" Whitworth bolt, cut it down to about 1/2" long, drilled an axial through hole, and welded an AN-6 male fitting to the top. Then I took an AN-6 90 degree elbow (female to male) and drilled/tapped the male end 1/8"NPT into which I screwed an 1/8"NPT to gauge line adaptor obtained from Holden in the UK. Using a new oil line kit (from Holden also) I now have a working gauge.

[Mark Thompson]

Can anyone confirm the thread size for the oil line connection to the 4AD engine block. The 1/2 inch whitworth bolt thread is very close but seems too tight. I don't want to strip the block. Shouldn't this be some sort of pipe or tubing thread instead of a bolt thread?

Thanks,
Mark

[mikeyr]

I would assume its 1/2 BSP (British Standard Pipe) which is also 14 threads per inch but a slightly different thread cut, same as BSW but with rounded threads.

I can confirm it later if you still need it confirmed, hard to stick a tap in a block from work.

[Mark Thompson]

A 1/2 inch whitworth bolt is a tight fit and the threads seem to match at 14 tpi. The 1/2 inch whitworth bolt O.D is 0.500 inch. I agree that the 1/2 inch British Standard Pipe Thread is also 14 tpi but the O.D is a nominal 0.825 inch. Am I missing something? I am working from charts, since I don't have a 1/2 inch BSP fitting to compare.

Mark

[Mark Thompson]

I rechecked the threads on the whitworth 1/2 inch bolt and they are 12 tpi. The hole in both of my engine blocks are 16 tpi. I researched every pipe and tubing chart and could not find any fittings in the 1/2 inch range that had 16 tpi. Meanwhile, I had contacted our wonderful friend from across the pond, Bill Haverly, about the problem. Regarding the adapters for the engine block, he said, "My suppliers are looking into this but it's a coarse thread not much used today so I am not too hopeful. My guess is 1/2 BSF at 16 TPI."

I didn't have any 1/2 inch BSF bolts to try, since everything on my Singer seems to use 7/16" and smaller. However, I do have a set of BSF taps and dyes that includes 1/2 inch. I purchased a 2 inch long 1/4 inch NPT brass nipple with a body diameter of 0.560 ". I chucked it in my drill press and filed the unthreaded part down to 0.500 " diameter. I then screwed 1/4" NPT brass ells on each end of the nipple until no pipe threads were exposed. Then I cut the nipple in half and threaded the 0.500 portion of the nipples with the 1/2 inch BSP, 16tpi die. After grinding approximately 1/8 inch off the side outlet of the ells so that they would clear the engine block, I screwed the fitting into the block. It fit perfectly! I used a 1/2 inch copper washer under the ell. It tightened down and sealed against the block. This process yielded two adapters, one for each engine and I now have 1/4 inch NPT threads to work with. I used brass because it is softer than the cast iron block and if anything were going to strip, it would be the brass and my block wouldn't be damaged.

The brass 1/4 inch ells and nipple came from Lowe's Home Improvement. I purchased 1/8 inch BSPP by 1/8 inch NPT adapters fom fastfittings.com to connect to the rigid tubing from the oil pressure gauge. My local hydraulic hose supplier had no problem fabricating hydraulic hoses with a stainless steel braided sheath that would fit the NPT connectors.

This worked for me. I hope it can be helpful to someone else.

Best Regards,

Mark Thompson