Problem or paranoia?

[Ross F.]

I've been putting some miles on my rebuilt 75 roadster. The 350 was rebuilt with a roller cam.
Before I dropped the body back on, I put a mechanical oil gauge and temp gauge on it an ran it. 40 psi and 180f.
After the drop with the car gauges connected, I again ran it up and it showed 40 to 60 psi and 180f.
On my last drive my wife asked me if the oil pressure was too high. The gauge was showing 75 psi at driving speeds an not dropping much at idle. I did some detective work. I pulled the wire off the sender. The gauge pegged the gauge. Plugged in with the engine off the gauge sets at 20psi. I didn't ground the gauge. I read somewhere this could damage the gauge.
my first thought is always the worst. Like something wrong with the new motor. But I'm hoping it's a bad sender.
i can find any sign of other problems. The motor runs flawlessly, no bad noises or oil spewing out of something.
any thoughts?..

[Joe L.]

Re: Problem or paranoia?

I've been putting some miles on my rebuilt 75 roadster. The 350 was rebuilt with a roller cam.
Before I dropped the body back on, I put a mechanical oil gauge and temp gauge on it an ran it. 40 psi and 180f.
After the drop with the car gauges connected, I again ran it up and it showed 40 to 60 psi and 180f.
On my last drive my wife asked me if the oil pressure was too high. The gauge was showing 75 psi at driving speeds an not dropping much at idle. I did some detective work. I pulled the wire off the sender. The gauge pegged the gauge. Plugged in with the engine off the gauge sets at 20psi. I didn't ground the gauge. I read somewhere this could damage the gauge.
my first thought is always the worst. Like something wrong with the new motor. But I'm hoping it's a bad sender.
i can find any sign of other problems. The motor runs flawlessly, no bad noises or oil spewing out of something.
any thoughts?..

Ross------


First of all, what kind of oil pump did you use? Was it a high pressure or high pressure/high volume?

[Ross F.]

Re: Problem or paranoia?

Hey Joe,
it was a melting pump with a 50 psi spring. I think basically Orem.

[Joe L.]

Re: Problem or paranoia?

Hey Joe,
it was a melting pump with a 50 psi spring. I think basically Orem.

Ross-----


Are you sure the pump had a 50 lb spring installed? Most of these pumps are supplied with a high pressure spring installed and you have to change that to the standard pressure spring if that's what you want. What model pump was it? Was it M-55, M-55HV, or some other part number?

[Ross F.]

Re: Problem or paranoia?

The BOM from the builder just says M55

[Joe L.]

Re: Problem or paranoia?

The BOM from the builder just says M55

Ross------


If you had someone else rebuild the engine, I would highly suspect that the oil pressure relief spring was not changed to the standard pressure spring which is usually supplied in the box with the M-55 pump. I actually recommend the installation of a GM #3814903 spring.

[Ross F.]

Re: Problem or paranoia?

Joe,
I will ask him. But it doesn't explain why I'm just now seeing the high pressures.
I'm going to hook up my mechanical gauge and see what it reads.
What will happen if it does have the higher pressure spring?

[Michael W.]

Re: Problem or paranoia?

I pulled the wire off the sender. The gauge pegged the gauge.

Which way? High or low?

Plugged in with the engine off the gauge sets at 20psi. I didn't ground the gauge.

99% sure this indicates a bad gauge. I assume you mean that you didn't ground the wire.

[Ross F.]

Re: Problem or paranoia?

Hey Mike,
Yes I disconnected the sender, opening the circuit, and the gauge went full scale.
At rest with engine not running, I read around 20 psi. low end if scale on gauge. I did not ground the wire, fearing gauge damage.

[Ken A.]

Re: Problem or paranoia?

Should be 0 with key off. you got a bad gauge.