Hi all,

I’m looking for some factory confirmation on the oil pressure sensor thread.

I’ve seen 2 different thoughts so far:
Blocks for cars with warning light sensors had a 1/8 NPT tapered thread (27 tpi)
Blocks for cars with mechanical gauge had 1/8 BSP parallel thread (28 tpi)

The majority of the aftermarket mini sensors and fittings appear to be 1/8 NPT. This includes the t piece sold as “TP” from most mini shops and the adapter “OA”.
https://classicmotoring.net.au/oil-gaug ... e-adaptor/


The part CAM6431 and original 2A269 have the parallel thread


I bought a T piece fitting from mini king many years ago which screws in fine but it’s the 1/8 NPT thread

The 850 parts manual has a sensor HYL2445 with washer 6K464 which suggests a parallel thread. I’ve checked on the old 850 engine under my bench and it has this setup


Or should I just use the NPT threaded adapter with some thread sealant and stop over thinking it? The NPT fitting hasn’t leaked so far. I’m currently using an 1100 van block from about 1970 which I’m assuming would have been a sensor light only

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Blocks for cars with mechanical gauge had 1/8 BSP parallel thread (28 tpi) - [cooper S] and part CAM6431 and original 2A269 have the parallel thread. See my picture below. The old T piece I ran in the late 70's had a parallel thread into the block and 1/8-27 npt for the other two. I used the old oil pressure sensor(pictured -npt) and used tape for the 1/8 bsp-28 mechanical oil pressure adapter. Worked fine. I bought a new T with all npt threads to use on the current build (with the new 20psi pressure sensor), not realizing it would not screw correctly straight into the block. Ideally need an adapter(T) with a male 1/8 bspp , female bspp and 1/8npt would do the job using std parts.
edited: I don't know whether a 1/8 bspt T adapter like the one raceworks has would solve the problem (RWF-809-02SS)

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1970 Mk2 Cooper S under restoration

Thanks for your help!

The raceworks item looks interesting, although I’m not sure on the compatibility between 1/8 BSPT and BSP

Following on from the raceworks googling, I’ve found a 1/8 BSP to 1/8 NPT adapter which is also available in brass from other places. This would make a good transition from the factory block to the aftermarket sensors and t pieces
https://aeroflowperformance.com/af925-0 ... to-1-8-npt

My main issue turns out to be the new nylon line kit. The old line had the “olive” style fitting on the left of the photo and the new one is the flat fibre washer type on the right.

The sealing area is minimal on the current bass fitting I have which screws into the T piece, compared to the back of the gauge. I think an “OA” adapter is needed

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