71 Z/28 Normal Oil Pressure?

[Ret_LTC]

Hello All,

My project is almost complete but my oil pressure seems to be low. The previous owner installed a mechanical oil pressure gauge. Is it the stock CSB 350 and after warmup, it idles at 700rpm - 12psi, rev it to 1,500rpm - 20psi. Anyone got a spec sheet on this?

 

[George-CZ]

There are a lot of factors that would be worth mentioning.
What oil and viscosity are you using.

Does the engine make any noises that don't belong there at this pressure? Knocking or like a sewing machine?

If the engine sounds normal, I would try changing the gauge to see if it's reading the wrong value.

What does the gauge read after a cold start? You should see something around 60 psi. After it warms up, something around 30 psi at idle.

And where is your pressure gauge connected? Under distributor? Or bahind water pump...? Or...?

 

[Ret_LTC]

Thanks for the reply...
Synthetic 10-30W oil
Engine sounds normal
My friend attached a test gauge along with the dash gauge and they both were consistent from cold start to warm engine idle
Cold start, @ 50psi, after it warms up, it goes down to 12psi at idle (700 RPM)
Oil Pressure connector is at the back of the block between the intake manifold and distributor.

I found a spec book (possibly from this site) that is a pdf of an original manual for the 1971 Camaro and it says, it should be, "40 PSI @ 2000 RPM".

Since I previously tested to 1500 RPM and only got 20 PSI, I doubt, I'll get another 20 PSI with just an additional 500 RPM.

 

[George-CZ]

Is that engine newly built?

I'm not a fan of checking the oil pressure at this location, but the good news here is that you are measuring the oil pressure output from the pump, which is a few inches below your mechanical gauge input.

I think the problem is somewhere in the oil pump.

Worst case scenario would be a knocking noise at idle and low oil pressure, which would be a high probability of damaged crankshaft bearings.

If the engine is in the car, I would loosen the engine mounts, lift the engine so that the oil pan can be removed, and check the oil pump. Clean the strainer, check spring, and last but not least check both oil pump gears.

 

[Ret_LTC]

I’m checking at the same point as the sending unit gets its pressure. No, the engine is original (40K miles). I’m reading a lot about synthetic oil causing lower oil pressure.

 

[George-CZ]

If your block allows it (made at the Flint foundry), I prefer to measure the pressure at the water pump.

But at this point it's irrelevant because the low pressure is already at the very beginning of the oil gallery.
I don't really believe it, but going back to mineral oil and doing a test is the easiest first step at this point.

Personally, I would choose Valvoline VR1 w40 or 50 oil with the necessary zinc package for flat tappets for this engine.

 

[rocket dawg]

10w30 or 10w40 is fine. Valvoline VR1 is what I use. Rule of thumb is 10 psi for each 1000 rpms. What weight are you using?

 

[G72Zed]

Pressure is a resistance of flow....and from the rpm/psi trends you are seeing, you do not have a flow issue, so you are getting good lubrication on cold starts, but the low psi showing does not give most the confidence due to what they see on the gauge.

It could be a number of things, like the pressure relief spring is acting up, excessive pump clearances or the engine is a tad on the "loose" side.

I would try a thicker oil just to see how it changes, I'm not one for using thick "racing" oils in street cars, but maybe the
Valvoline VR1 20/50 would show the changes you would like to see.

 

[George-CZ]

10w30 or 10w40 is fine. Valvoline VR1 is what I use. Rule of thumb is 10 psi for each 1000 rpms. What weight are you using?

I use 5w50. I don't recommend anything I haven't tried myself. And 50 because VR1 is not available here in the 40 class.
I have a looser engine .002 on crank bearings with a HV Melling oil pump with 10% more pressure than stock pressure.
I get about 25 psi at idle.

 

[Ret_LTC]

If your block allows it (made at the Flint foundry), I prefer to measure the pressure at the water pump.

View attachment 214321

But at this point it's irrelevant because the low pressure is already at the very beginning of the oil gallery.
I don't really believe it, but going back to mineral oil and doing a test is the easiest first step at this point.

Personally, I would choose Valvoline VR1 w40 or 50 oil with the necessary zinc package for flat tappets for this engine.

Thanks, nope, don't have the ability at the front. I will definitely check out the VR1.