Late Noton Oil Pump G80CS - oil inlet/return which way?

[catalina500]

Which is which when looking at the two oil ways/unions? I assume the "lower outer" is the feed from the tank and the "upper inner" is the return. That is what the illustrations for the plunger oil pump engines suggest but i cant find a similar illustration for the Norton pumped engine - thanks in anticipation

[mdt-son]

1964-66 singles used the small capacity oil pump NM15522, derived from early Norton twins (model 7, 77, 88, 99, also Jubilee, Navigator and Electra), while 1966-68 G80/85CS used the large capacity oil pump NM25396, derived from the Norton Atlas and G15 series, coupled with the 3-start worm gear. The part number given to this combination was NM25450.

When looking at the underside of NM15522, the oblong hole at the center of the pump housing is the oil feed from the oil tank; the oblong hole at the pump's driven gear is scavenge outlet from the pump, and the small hole farthest away is the scavenge inlet from the sump.

By poking with a clean spoke through the union and oilway, you will easily find which union is for oil oil feed, and which union is for oil return.

A small article by John Hudson on Norton oil pumps is enclosed.

- Knut