Author Topic: Oil union o-rings  (Read 230 times)

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Oil union o-rings
« on: 15 September, 2021, 12:45:28 »
Hi all
I have a B40 SS90 distributor engine, on which a previous owner has converted the standard oil pipe union which used a conventional gasket  (feed and return) to the union from later model which is sealed with 2 o-rings.
Can anyone tell me what the o-ring size should be? A 5x2mm fits but doesn't seal very well, but I'm reluctant to fit a 5x3mm in case I restrict the oil feed.
Wondered if anyone has knowledge. I can't find a spec in any of the documents I have.
63 B40 SS90 in C15C frame.


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Re: Oil union o-rings
« Reply #1 on: 15 September, 2021, 21:22:58 »
If the union is the same as the A65 they should really be squre section rings. I couldn't find any in this country but they are available in USA. If you look up 010 oring/seal size all the info you need is there.


  • Golden Flash
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Re: Oil union o-rings
« Reply #2 on: 15 September, 2021, 21:56:10 »

The 'O' ring spec for A65s did change to round section in the later oil union.  I would imagine that the A65 and the unit single would use the same 'O' ring.  Part numbers will probably be different though.
They do not squash that much but seem to work.