oil pressure too high?

[callbald]

What is the danger of 39 flathead with too high oil pressure. since changing the pressure relief spring and plunger, oil pressure cold reaches 70 at 40 mph and when warmed up runs 50+ at 45-50 mph.

This is the other problem i have with loosing pressure with hard stop.

[Drbrown]

My '47 59AB engine has an 80 lb pump and reads 70 when cold at idle. It won't go higher so its relieving the pressure at that point. When engine is hot it reads 20 to 25, and on highway around 45 to 50. I use 10w-30 oil/no filter and engine runs at about 185 degree.

Aside from your previous thread which talked about missing baffles, what is the viscosity rating of your oil and your running temperature.

[callbald]

Before I replaced the oil pressure relief plunger and spring pressure read 15 at idle and 30 on the road when hot. I assumed the engine had a 50# oil pump since the pressure was not that high compared to now. Just concerned about damage at that pressure level

[Ol' Ron]

This has been addressed several times here and I don't think a number is available. I don't like hi oil pressure because it's bad for the bearings and crankshaft. The 50/70 lbs of pressure is forced through a very small space when leaving the bearing. And in a flathead with unfiltered oil, the small particles in the oil will "sand blast" the bearings and the crank. Over time it can contaminate the oil to an extent that it soes more harm than lubrication. Especially a cast iron crank. The designers of the engine have specified 10 lbs at idle and 40lbs in cruise. These number vary in some publications.

[JWL]

The pressure you mentioned is completely safe.

[big job]

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I have the same problem 80lb cold. But I always idle any cold engine no matter what
year, then about 5-10 minutes it settles around 60lb then to 40-45 and 25 idle hot
and my hot is a cardboard infront. Its May & still need a global warming cardboard?
Not to mention long johns. Anyway, I thinking 80lb pump clearances in specs. I may
have a 80lb spring; makes sense it will blow off at 80 right: And a 50lb spring will
blow off at 50Lb or it should. Then when hot and clearances start dancing around that valve should be closed and oil pissing out of clearances and the pump pumping
50lbs. My brain is old but when young we rebuilt more I can count Mopar flatheads
first thing on those, worn cam bearings and there goes the oil pressure. No washers or stretching relief springs will cure that...Anybody here remember "rubber crank"
mopars. I do

[4t8v8]

Yes I do. Also remember when overhauling a Ford flathead 6 to be sure and replace the cam bearings. Otherwise - low oil pressure.

[flatford8]

Originally Posted by callbald

Before I replaced the oil pressure relief plunger and spring pressure read 15 at idle and 30 on the road when hot. I assumed the engine had a 50# oil pump since the pressure was not that high compared to now. Just concerned about damage at that pressure level

I would be happy with these numbers. Unless I had to take it apart for some other reason, I'd be going down the road in it. Did it lose pressure on a hard stop with 15# and 30#?. Seems like another problem has been created..... Mark

[Ol' Ron]

The reason why I don't like hi oil pressure is because I come from a stock car racing back ground. After we lowered our oil pressure, we stopped having bearing and crank problems. This is why experience teaches you something/ One thing high oil pressure does is keep the oil hot.

[rotorwrench]

The aircraft engines can be adjusted pretty high on oil pressure but we try not to let them get over 75 to 80 psi at top rpm when warmed up. It has a tendency to wash out the rings due to the piston squirts that most of the large or higher compression engines have.

Those older Ford V8 engines still had the lower psi oil pressure indicating system. I don't know if it would hurt that indicating system sender or not but it would peg one out during the warm up with a pressure higher than 40 psi or so. The later ones were 80 psi so it wouldn't have much affect on them.

Ford generally ran SAE 20W20 from new on the flathead engines. SAE 30 was for hot weather use.

[Frank Miller]

As Ron said, pressure adds heat to the oil. One of the jobs of the oil is to remove heat from the bearings. You end up working against yourself after a certain point. If everything is built to specs you're probably ok.

[callbald]

The only time ther pressure fell to zero was on a firm stop. Pressure was not low while driving. The excessive pressure may be the spring is an 80# not 50# as ordered and shown on the packaging. Wonder if there is a simple way to validate the right spring was in the bag. Hit the road for a long drive from Leo, in to Auburn - maintained pressure averaged 20# idle and 45# at 50 mph. no pressure problem with easy stopping.