Oil pressure drop

[russo1]

My rebuilt 54' 235 just turned 1000 miles. At start and while cold it idles at 30 and will reach 45 with increased rims

After running 10 minutes and Running hot it idles at 5 to 7 and the needle will move slightly with increased rpms.

Looking for what normal is ....and comments on why pressure is so low while hot.
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[Wrenchbender Ret]

That seems like the pressure of the old splash system engine. Was it an exchange engine? Could someone have substituded an older engine for the original 54?. You might try a heavy weight multi vis. oil like 15w40.

[AZ59apacheguy]

Did they install a new oil pump, or just slap the old one back in?

[OrrieG]

My experience with 235's dates to the mid 60's. All I have had or observed had the oil pressure guage/tach. They have a very good oiling system that has pressure that varies with RPM. In my opinion 8-10 psi at idle is nothing to panic about. Warmed up off idle you should get about 25 psi which is adequate because the engine is designed for that. If it is really hot go to a heavier oil in the summer (I ran 20-50 in the summer when we lived in Phoenix area). If you are only getting a little above 10 off idle then I would suspect they did not replace the pump. Might also have bearing clearances that are on the generous side too.

Another thought, are you using the stock gauge? Might but an after market gauge on it and make sure the original is accurate.

[dwcsr]

Originally Posted by russo1

My rebuilt 54' 235 just turned 1000 miles. At start and while cold it idles at 30 and will reach 45 with increased rims

After running 10 minutes and Running hot it idles at 5 to 7 and the needle will move slightly with increased rpms.

Looking for what normal is ....and comments on why pressure is so low while hot.
Posted via Mobile Device

I would check that the gauge is accurate. The 54 was an odd system with to many parts that could suck air. It was half dipper system and half full oiler system. It didn't use dippers but used the dipper oil pickup to block piping and the old style long pump and a pan unique to 54 only. Any of the pickup tubes or even the pump cover could suck air if they didn't use a gasket. In 55 it changed. Worse case drop the pan check the piping and check one bearing for clearance. At 1000 miles it still should be 25 30 hot idle.

I realize that 1 lbs per hundred rpm is acceptable but not on a new motor