Model 18 oil press gauge…has anyone?

.....the oil pressure requirements for the roller big end are so low, relative to a plain bearing engine, that it hardly seems worth the effort. Got a good steady return to the oil tank? Everything is likely fine. Good volume of oil on the move.

They don't have much oil pressure. Just oil flow.  Possibly why Singles had oil pumps made of Mazac, and twins (with shell big ends) have them made from cast steel.

The OHC race engines are supposed to have something like 8 to 12 psi in the feed pipe to the camshaft.   Picture shows my test setup.  pressure is built up by forcing the oil flow through the cam feed jet.  The cranks of all Singles have a similar end feed so they must have similar pressure on the pump side of the jet.