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A-Series Oil Fitting Thread Size

Mon Mar 31, 2014 6:01 pm

What is the thread on the fitting for the oil filter (normally has a banjo fitting) that is located right above the oil pressure sensor port?

I thought the answer was 3/8 BSPP but apparently I was wrong. I ordered one of these and it won't fit: http://www.mcmaster.com/#4936k123/=rc6ytp

Its major diameter is about 0.030" larger than the major diameter of the banjo bolt's threads.

Re: A-Series Oil Fitting Thread Size

Tue Apr 01, 2014 7:44 am


Assuming that you are converting to AN plumbing this is the fitting you need http://www.minimania.com/part/C-2A715/Fitting-5-8-18-To-An10-W--Washer .

Alternatively, many re-tap that hole with a 3/8 NPT tap and then use the common 3/8 NPT to -10AN fitting. Of course this is best done when it is a stripped block so that you can be sure that you have all of that grunge cleaned out of the oilways before assembly of your engine.


Re: A-Series Oil Fitting Thread Size

Tue Apr 01, 2014 10:10 am

Thanks Mack.

Something about forest and trees - I was fixated on BSP threads and didn't even think of that route. :oops:

Going from the size of everything on the engine, I was going to do 8AN but since they have a 10AN fitting I'm questioning whether I shouldn't return the smaller stuff and re-order in 10AN. It seemed too large based on the size of the ports in the block but it would make it a lot easier.

Re: A-Series Oil Fitting Thread Size

Tue Apr 01, 2014 10:23 am


I use -10AN for all of the oil line plumbing: oil pump out --> remote oil filter (< --> Accusump) --> oil cooler --> block oil galleries. Although -10AN looks big on the outside it is still only 1/2" ID.
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