I have a 74SB with a new rebuilt engine (JC Whittney HD oil pump), the oil pressure is about 5psi at an idle when hot and about 25 psi at 2500rpm measured with a mechanical oil pressure gage. My question is, with the idiot light pressure switch in the engine the light flickers on at an idle but is off with a little higher rpm. Should I not worry about this or try to get the oil pressure higher at the idle. What is the recommendation. thanks.
Not to worry. It's normal in hot summer weather.
Fortunately, at idle there is almost no load on the bearings and very little pressure is needed to keep them happy.
What is your idle speed? It is normal to have VERY low oil pressure at idle, but the light should not come on. It is an indication of worn bearings allowing oil to escape too easily. The warning light also comes on at a very low pressure, personally I would adjust the idle speed a little higher to "hide" this problem, and ensure proper lubrication, until I have time to rebuild the engine.
You could also try thicker oil, like 20W50 or straight 30W. Stay away from ultra cheap oils, and synthetics. Synthetics have low viscosity, they don't help with pressure in your case.
Jan
The switch will open between 2.1 and 6.4 psi. Your pressure seems low, across the board, although it does depend on what type of oil you are using.
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