Oil Pressure Question

[93CalypsoConvert]

I recently bought a 93 fox with a carbureted 5.0. The engine was apparently rebuilt, but I do not have proof. It looks brand new under the valve covers and the pushrods are a different brand. My only concern is the oil pressure. Cold idle is 50, hot idle is 15. Its not making any concerning noises. Previous owner claims it has a melling oil pump and new mains. There is no metal shavings in the oil, no copper. 2000 rpm cruising is 40 psi. Measured with mechanical gauge.


Another weird thing is it will NOT go past 50 psi. When cold, it goes to 50 and stops. Cold idle at 800 rpm = 50psi, Cold at 2000rpm = 50psi. Weird

 

[elarm1]

Is it an electric or mechanical gauge? Or stock gauge?

 

[93CalypsoConvert]

Is it an electric or mechanical gauge? Or stock gauge?

Mechanical.

 

[7991LXnSHO]

It sounds like the bearings are a bit worn, but 15 hot at idle will still be fine. How much does the pressure go up as the rpms go up?

 

[93CalypsoConvert]

It sounds like the bearings are a bit worn, but 15 hot at idle will still be fine. How much does the pressure go up as the rpms go up?

Goes to about 40 at 2000 and then slows down after that.

 

[7991LXnSHO]

Sounds fine for a worn engine. If compression and leak down tests are good, I’d drive it, saving for or bench building (racing) an eventual replacement.

 

[93CalypsoConvert]

Sounds fine for a worn engine. If compression and leak down tests are good, I’d drive it, saving for or bench building (racing) an eventual replacement.

That’s the part that bothers me. It’s a fresh engine. It has great compression. I think the owner put oversized bearings in. Oh well I’ll keep driving it and not try to worry too much.

 

[elarm1]

send it!

 

[7991LXnSHO]

There’s probably a lot of life in it, and the loose mains are the reason for a new pump. I would not spin it to the moon regularly, but overall it sounds healthy.

 

[Mustang5L5]

What oil viscosity are you running?

 

[93CalypsoConvert]

What oil viscosity are you running?

10w30 synthetic

 

[Steel1]

15psi hot on a new build is low imo.

 

[HemiRick]

10 PSI per thousand RPM and you're fine.

 

[General karthief]

That's low for a new build.
I'd run it if I had to but it would worry me.

 

[revhead347]

10 PSI per thousand RPM and you're fine.

Correct, you are fine. As long as it comes up off idle, it's fine. There isn't much load on the bearings at idle.

Kurt

 

[marcelo]

with Melling HV Pump it had 60psi ..droping a little when hot at idle ..and now I run a Melling High Pressure and it runs at 80psi at cold idle drops a little when hot at idle ..
10/40 synth.. went back to stock sending unit with low pressure warning light ..

 

[HemiRick]

Thats crazy high pressure just wasting energy heating up the oil.

 

[marcelo]

using the Melling HP pump over the HV ..was recommended by a known engine builder ??!! i dont know .. engine runs great no problems so far ... and no temp problems with oil or engine ... unsing synth oil ..temp doesnt matter anyways..

 

[7991LXnSHO]

Following the advice from post #2 is a great idea.