high oil pressure?
 

While giving my engine a compression test (120lbs on all, after valve job) ,I noticed my newly installed mechanical oil pressure gage read 90psi ! the electronic gage in the car only goes to max 80psi, all of a sudden it dropped to 65lbs and maintained that while on the starter.
So I think my oil pressure relief valve must have been stuck because every time I crank it now it reads 65psi.

So, my question is how much do these little flathead oil pumps put out??

picture

Re: high oil pressure?
 

Stock oil pump or a new Melling pump? Which Melling?- M-15 High Volume or M-19 Standard Volume?

Oil Pressure vs. Flow (PDF)

Nice looking EAC Merc Flathead....

https://www.fordbarn.com/forum/attac...2&d=1586727426

Re: high oil pressure?
 

The new production Melling pumps will put out 80 PSI I have found the standard replacement M-19 and the high volume M-15 both have the same pressure relief spring. Testing each of these pumps on my test stand have shown this pressure. The original design Melling high volume pump produced in the last century the M-21 will produce 100 PSI at the same RPM testing i do with the above pumps.
Ronnieroadster

Re: high oil pressure?
 

What rpm does a flathead oil pump turn at ? Half speed of the engine?

Re: high oil pressure?
 

The oil pump is driven by gears on the cam. The cam turns at half the rpms of the crankshaft.

Re: high oil pressure?
 

Is it one to one off the cam with the idler gear. Just wonder with testing one on a test stand what range is considered correct to show its bill of health. High and low

Re: high oil pressure?
 

It takes a noticeable difference in gear size to make much of a change in gear ratios, think ring and pinion gears or the crank gear versus the cam gear. It is about tooth count on the drive gear vs the driven gear. It is difficult to get much of a difference in tooth count without a corresponding change in the relative size of the gears. I really don't know what the tooth count is on the gears and there is an idler gear between them, but just looking at them it looks like it would be close to 1 to 1 between the camshaft and the oil pump.

Re: high oil pressure?
 

During my testing to figure things out I find the oil pump is turning 1/2 engine speed by the idler ratio. It takes a lot of torque to turn the pump 3000 RPM using 10/30 weight oil.

Re: high oil pressure?
 

An oilpump can take 2.5-5% of an engines power so it takes some power to drive it full out.
Eco engines now run variable oilpumps.

Re: high oil pressure?
 

Ronnie. what is the length of the pump relief spring (standard ford pump)

When I take mine apart I want to check the spring and maybe replace it ?..thanks

Re: high oil pressure?
 

Look in the Ford service books, it gives the poundage and at what length compressed of the spring.
Let me know if you cant find it, those pages are still open on my workshop desk.
Lawrie

Re: high oil pressure?
 

can you please post it Lawrie as I don't have a copy of the ford service books.
thanks

Re: high oil pressure?
 

specs are
78-87 ounces force at 1.38 inches
Lawrie

Re: high oil pressure?
 

Thanks Lawrie