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Oil pressure is good once car is running for a while. Do others with 356 engines experience this slow build in oil pressure, (one minute) ? Completely cleaned oil filter and blew out tubing to and from oil sending unit also to filter and return line to block. Changed oil and filter and the oil is amazingly staying almost clear, not dark brownish black like drained oil. Checked bottom pan through the drain hole with a long screwdriver and pan bottom seems clean and screwdriver did not have any sludge on it when removed. So system seems clean and pressure builds to 50 psi when rpm is around 1000-1500. When engine is hot and at idle (500 rpm) oil pressure is just below 40 psi. Could this mean the pump is weak and should be rebuilt? Would appreciate any information.
Thanks

Bill,

You have oil pressure readings that many of us with the 356 engine envy. I can get an oil pressure reading on an auxiliary gauge by just cranking the engine without starting it. My stock gauge reads slower and lower than the auxiliary gauge.

Suggest you temporarily connect a direct reading (mechanical) oil pressure gauge, to compare with the one in the instrument panel. This can be easily done by connecting into one of the main bearing oil gallery port sites on the lower RH side of the engine, or with a tee fitting at the same site as the stock sending unit. The main bearing port sites are tapped for 1/8" NPT plugs. My auxiliary gauge is connected to the port site for the rear main bearing.

A noticeable difference between the two gauges would invite checking the sending unit or gauge unit, or permanently connecting an auxiliary gauge for an accurate reading.

(o{}o)

What kind of oil are you using? If it is thick oil it may take time for it to warm up and circulate. This is very bad for any engine.

JW, great advise, did you install an adapter to go from 1/8" NPT directly to the fixed oil pressure gauge? Am going to drop the pan hopefully next week to insure that the oil pump screen is clear and that the screen assembly is connected to the pump suction.
Thanks, Bill

Bill, car is not at home now and memory of this is not good, but believe there was an adapter to go from the 1/8" NPT thread in the engine block to the oil gauge line. It was a conventional connection, nothing special as I recall. I used a Stewart Warner mechanical gauge.

Also, as posted on the Packard Club site: I use, as many here do, a 15W-40 engine oil in my 356. I use the Classic Motor Oil sold by the Indiana region of the CCCA. Others here use the Shell brand. Either should work just fine. The 15W gives good oil flow at cold temps and the 40 provides good protection at operating temps. You should not need any oil that has a higher viscosity than 40W unless your engine is badly worn.

(o{}o)

JW, thanks good advise.
Bill