low oil press????

[pwilletts]

I have a very simple 1 cyl diesel ...when starting the oil press is about 85# which is correct.....after about 15 min of running at normal speed the press is down to 40...at speed....the engine only has one bearing that gets oil under press from the pump..the front crank bearing...all else is splash fed....very simple....new bearing in the con rod..all else ok....running 10-40 weight ...going to go to straight30 and see...any ideas.....its not the pressure relief as its a simple spring against a reed style valve....engine temp seems normal..no light.......its a k34 Farrymann fyi

[Wotname]

Is this something new that has occurred or has it always been this way?

To my mind, 85# seems high at start up, I would have thought the oil pressure relief valve would have kicked in before 85#.

Yet 40# at running temperature seems normal to me.

What does the manual say it should be?

Can you trust your gauge?

[Wotname]

Another thread
Farymann K34 oil pressure - SailNet Community

[a64pilot]

I don’t know that engine, but for a generic engine 40is fine.
However assuming that is an old design I think a straight weight 30 is likely a better choice than a multi vis oil.