8CM high oil pressure?

[50MercMetalHead]

I fired my Flathead for my 50 merc up today for the first time. For some reason I’m getting 50-60psi of oil pressure at idle. Revving it up will move it to about 70, maybe 75. I’m thinking there is something goofy.

I plastigauged all the rod and main bearings when I assembled the engine, they all checked out at around .002-.0025. Cam bearings I couldn’t check cause I don’t have a bore gauge, they felt a hair tight, but I could still spin it by hand without too much effort.

Oil pump is a new Melling M-19 from speedway.

I had done the 95% oil mod, and had 1/2”(AN8) hoses and fittings going to a k&n spin on filter. I removed the lines and internal plug, it’s reverted back to stock oiling now, and if anything that made the pressure go up a few pounds.

I’m confused. Any ideas?

[Phil Gillespie]

What weight oil are you running? After a new build some rin in oil or at least a lighter weight oil. That pressure considering a rebuild with a high volume oil pump is up there but in my opinion seems ok. Oil also would not have reached an operating run temp, will give a slight pressure drop off.
Phil NZ

[50MercMetalHead]

Running 10w30, forgot to say. The M-19 is standard volume.

[19Fordy]

50MercMetalHead: What is the oil pressure after the engine is at operating temperature both at idle and "on the road"?

[50MercMetalHead]

I haven’t run it up to temp yet. I was going for a few laps up and down the driveway but I had to stop and fix something on my exhaust. I will let you know once I can get it up to temp. I did notice just now before I had to stop, it had dropped to about 40 for a moment, before going back up to 55.

[alanwoodieman]

Sponsored Links (Register now to hide all advertisements)

did you use a known mechanical gauge? my 51 merc engine reads high when cold but drops to 60lbs running down the road, 30lbs idling hot. if by chance you used the electric gauge-do you have an 80lb sender?

[50MercMetalHead]

I get the same reading on 2 different mechanical gauges. For a moment I thought that may have been the problem, but the gauge is fine.

[tubman]

Sounds like someone shimmed or stretched the relief spring.

I'd replace it.

[50MercMetalHead]

Ok, I’m having temp gauge issues, but I’m positive that got it up to temp (no way it wouldn’t be up to temp with 180° stats and no heater cores), I drove it probably 4-5 miles, it was running for probably 30-45 minutes. It runs really good btw. I’m seeing somewhat more expectable pressure now. 20-25 at idle, and 60 at cruising rpm.

[Kilohertz]

I have had my '49 F-47 for about a year with a C1BA and from the time I first started it, with a good mechanical gauge screwed right into the engine block, I get 50 PSI at start up and doesn't really drop much after it warms up. Haven't been able to drive it yet,it may drop after it runs for a while.

cheers

[19Fordy]

Sounds like things are getting better. Keep driving it.

[big job]

Looks like a healthy engine in my book thats exacty what mine runs at now 7,000 miles
no changes.

[Bored&Stroked]

I don't see anything wrong with it . . . just drive it as is!

[50MercMetalHead]

Well I put about 50miles on the car today, just cruising in town so a few hours of driving. Seeing 22-25psi at idle, 40-50 at cruising rpm, and about 70 when I really get on it. I’m happy with those pressures, and it runs great, so I think all is good. I appreciate the help guys. Felt great to drive it again.