Late twin Oil Pump

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Late twin Oil Pump

Postby GrimJim » Fri May 03, 2019 3:44 pm

I wold appreciate some information concerning the last version of the twin oil pump which has the relief valve in the base plate. The pump I have was refurbished by Ray Spencer and
the setting of the relief valve was noted on the baseplate as 95 psi. I recently checked the oil pressure and it was around 200 psi at tickover on startup with cold 20w/50 oil. I
took the pump off and removed the delivery pump to check the oil passages. I have attached a photo of the section of the base plate where the delivery pump is mounted (one) and a photo
of the base plate from the back with the internal oil passages indicated (two).

I was searching for the connection between the discharge port in the baseplate and the relief valve via the horizontal passage (in red), but all I have found is a very small hole in the discharge port of the pump
indicated in photo one which links to the horizontal passage. In my opinion this would give a very restricted flow via the relief valve. Can anyone who has an intimate knowledge of the operation of these
pumps enlighten me, please?

Jim
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Re: Late twin Oil Pump

Postby Duncan » Fri May 03, 2019 6:55 pm

Hi Jim

On earlier pumps that is just the drilling to prime the return side of the pump, as you note a relief would have to be a larger passageway.

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Re: Late twin Oil Pump

Postby GrimJim » Wed May 08, 2019 2:29 pm

Thanks Duncan, that's confirmed what I thought. I was confused as I didn't see how this base plate would have been drilled like this, as it has been cast and machined to accommodate a relief valve.
It was also surprising that the refurbishment didn't pick it up. I managed to get hold of another late pump and found as you suggested that the hole was much bigger (see photo).
Unless anyone else has any better suggestions, I will drill a hole of the same size and see what happens.
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