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I'm on another engine rebuild, and was mucking around with the oil pump yesterday-
The relief valve was worn to the point of rattling around in the bore. So I cannibalised a red motor oil pump for the relief valve and spring. The red motor relief valve is longer than its grey equivalent, but the diameter is the same, and the total height of the spring (in the piston) is about 1/8" less for the red than the grey. The "thumb dynamometer" told me that the two relief valve springs have about the same stiffness, so I put a couple of washers in behind the red motor spring and installed the red relief valve and spring in the grey oil pump.

What's the received wisdom on this topic? Has anyone used a red motor relief valve and spring in a grey oil pump? I suppose I can drive the pump with a drill and measure the oil pressure with a gauge once the engine's assembled.

And a red motor's oil pump relief valve plug makes an excellent sump plug for a later grey, as I also discovered.

Rob

Hmmm - backyard engineeering has netted some good results over the years, be interesting to see how the oil pump performs .....

Very interesting!
I’d love to know how the red motor relief valve is holding up in the grey pump!

I ran the motor with a gauge instead of the oil pressure switch, and the oil pressure was at least 30 psi. I figure I guessed the washer stack depth fairly well. Oh, and the oil pump gears were quite worn too.

So, yes, it appears that you can use the red motor relief valve and spring in a grey oil pump.

Rob

Good information! Thanks!