Low oil pressure can be blamed on a number of things but untimately will probably end up being a tired engine with worn bearings. I assume the 25 psi pressure you refer to is at driving speeds not idle. At idle this would be fine.
Many people dismantle the pressure relief valve and shim the spring with a couple of washers. This raises the relief pressure to about 55 psi. However if your pump/bearings are worn this will not make a difference.
20/50 is the correct oil. Do you know how many miles are on the motor?
John
You wrote:
>
>Im new to the mailing list, and just now getting back to finishing
>restoration of a Series 1 Alpine I started ~15 years ago.
>
>I started by running 10-30 oil (leaked too much and resulted in low
>oil pressure) I changed to 20 50, and get approx 50 psi on startup.
>Once engine is hot (15 minutes on the highway) oil pressure slowly
>drops off to approx 25 psi. I dont want to run the engine until this
>is resolved. Suggestion Ive gotten so far was to check the oil
>pressure relief valve. The engine has an non-original oil filter
>base for a modern oil filter (fram ph16 currently installed) and
>therefore the base is not the same as original (although I have 2
>original bases with cartridge type filters). Adapter plate has
>"Crysler" stamped on it ...I assume this is from later days when
>Crysler was involved with Sunbeam. Alternate suggestion was to pull
>the oil pump and check the clearances.
>
>Questions: Can anyone confirm this adapter base is acceptable? (it
>looks like a good fit and doesnt leak) Do I need a special pressure
>relief valve for this base or did it come with only one spring value?
>(stock valves are larger diameter and dont fit...also stock unit felt
>a little stiffer when I pressed on it with a screwdriver) ......If
>the pressure relief valve checks out OK, does anyone have any
>suggestion prior to pulling the oil pump?
>