Oil pressure at idle

[RRMs69Z]

is it normal for the oil pressure in a 302dz to drop to around 10 on the gauge when the engine is warm and is idling, for example when I sit at a red light?  As soon as I give it gas the pressure goes back up around 45. If this is not normal, any thoughts why this is happening?  Thank you.

[bcmiller]

What oil are you running?

[ZLP955]

As much info as possible would help with ideas - but initial questions are:
Is this with factory gauges? Has the engine been rebuilt in the last few years? Is the low reading on idle a recent thing? Is it only low when the engine is warmed up? When was the last oil and filter change?
I would try replacing the sender unit first, to rule that out. If that doesn't change readings, and the engine hasn't had any recent work, then it could just be larger clearances due to wear - then a heavier weight of oil may help in the short term. Oil pumps are fairly reliable (simple operation, well lubricated....) but could be the culprit.

[RRMs69Z]

The engine was just professionally rebuilt, I have less than 300 miles on it. I just changed the oil and filter to rule that out. I used the classic ac delco PF25 filter and Shell Rotella T4 15W-40 oil. The block and heads are original but the block was bored .20 over.   Although engine has new internal parts we used parts that resembled original parts. Like a solid lifter cam. The instrument gauges on the floor are new. When the oil pressure drops at idle the temperature gauge goes up, not in the red, which makes sense to me. I was told I should use a 160 thermostat.

[RRMs69Z]

I have read that 10 to 15 pounds at an 800ish rpm idle is fine, but like a new parent I just need reassurance that everything is fine.

[L78 steve]

Just to be safe keep an eye on the pressure. If it drops any from where it is then a recheck is in order. Do you have the bearing clearances from the re-builder?

[WorkinProgress]

You say...."The instrument gauges on the floor are new." Are these repro console gauges?

                                                      - Warren

[maroman]

I would hook another known good gauge in the system to prove the new gauge is correct.

[bcmiller]

The engine was just professionally rebuilt, I have less than 300 miles on it. I just changed the oil and filter to rule that out. I used the classic ac delco PF25 filter and Shell Rotella T4 15W-40 oil. The block and heads are original but the block was bored .20 over.   Although engine has new internal parts we used parts that resembled original parts. Like a solid lifter cam. The instrument gauges on the floor are new. When the oil pressure drops at idle the temperature gauge goes up, not in the red, which makes sense to me. I was told I should use a 160 thermostat.

Tell your engine builder about it and see what he says.

[Kelley W King]

I would talk to your builder about the pump he used and what he thought it should run. A test gauge would be nice also.10 is ok but I too like to see 25 or 30 but my big blocks do teens or 20 hot. I run the 160 stats with 2 1/8 holes for air traps. Hot temps do thin the oil and lower the pressure. If all checks ok you might try 20/40 oil just to see if.

[RRMs69Z]

Thanks all.  Warren, yes, the floor gauges are repo. I will give my builder a call. I will let you know what he has to say.

[KurtS]

You need to hook up an accurate gauge to see what it is actually running.

[67jeffreyt]

On my rebuilt 67 350, I use repro factory gauges.  The lines on my gauge each represent 20 psi increments.  My engine cold shows between the middle and next high line.  As it get operating temp, my thermostat is 180, at idle the needle points and the second  line, which is 20 psi, because the first line is with the engine off.  Before I put the repro gauges in I had the dummy light and it never flickered or came on.  I use conventional 10w30 oil.  If this helps any, my pic is cold idle, I don't have a pic of engine hot.

[KurtS]

You need to hook up an accurate gauge to see what it is actually running.

And the factory gauge is not....

[Kelley W King]

I think the idiot light triggers at 6 to 8. I like them as an addition though because it is in your face while driving.