Oil pressure range

AngleT

AngleT

Always more tuning to do
I just got my "hot rod" running and I installed an oil pressure gauge. What range of oil pressure should I be seeing when it is at operating temp at idle? I do have the larger oil pressure relief spring from PBS installed, but I'm seeing (what I think) is low oil pressure at idle when warmed up.

Thanks,
 
I'm no oil expert...

AngleT said:
seeing (what I think) is low oil pressure at idle when warmed up.
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But if your engine/oil pump is healthy, and all other factors being equal, wouldn't the oils viscosity be the biggest factor here? What viscosity are you running and what pressure are you seeing?

(honestly, not that I could approve or disapprove once I have the numbers - I am just pointing out that you probably need to include those specifics in order to have this conversation)

Pete
 
I'm running Redline 15w-40 Diesel oil

When it's cold I'm running between 60-70psi. I wanted to see what what the general consensus was before I gave the low numbers to prevent tainting the results of the survey. The pressure comes back up between 55-65 psi when I'm driving and the car is warmed up. It's just when I'm idling at a stop light that has me wondering.
 
I use 5w30, but once warmed up I usually see 15-20 at idle. Mind you that's a standard oil pump in good shape on the 1800, and on a mechanical gauge so ymmv. Just curious as to why your running diesel oil?
 
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How much do your trust that gauge?

AngleT said:
I just got my "hot rod" running and I installed an oil pressure gauge. What range of oil pressure should I be seeing when it is at operating temp at idle? I do have the larger oil pressure relief spring from PBS installed, but I'm seeing (what I think) is low oil pressure at idle when warmed up.
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How much do your trust that gauge? Especially at the bottom end of its range? If you don't have a pressure test setup, stop by a garage that does and have them check.

There's a rule of thumb that says that 10 psi per 1000 RPM is about right for engines of this vintage.
 
Kinda like all have said here Eric... especially...

... the 10 pounds per 1000 rpm.

Little OP is OK a idle, as it doesn't need much... and as for the accuracy... well that is all relative also.

You need to LEARN what the engine's baselines are that are INDICATED on this guage and use them as a reference point. Then if and when there is a variance... that would be the time to worry or do something. That's why IDIOT LIGHTS have some value...

Try and have more fun WATCHING the road... HA!
 
+ 1

Usually minimal oil pressure at idle should be about 15-20lbs or so. I like to see 25, but that's not always the case, especially with an older pump and hot thin oils.

10-15lbs per 1000 RPM is a good measuring stick.

-M
 
Results are in

And I'm OK! I just didn't think there would be that big of a variance between running and idle. I'm seeing about 30 at idle, but that is given that it is idling at about 2K. I set the idle that high to compensate for when the A/C is on. When the A/C is on, it pulles the idle down to about 800 RPM.

The gauge is a brand new AME digital gauge, so it should be fairly accurate.

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FWIW, my oil pressure gauge in the dash has always indicated too low pressure, if you go by what the Haynes workshop manual has to say about the subject.

But then again the dash meter is way below zero when the engine isn't turning...

I think it indicates around 3 or four bar (kg) or thereabouts at redline. A bar is 14 psi I think.

And I'm using 5w50 fully synthetic oil.
 
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Black-Tooth said:
... the 10 pounds per 1000 rpm.

Little OP is OK a idle, as it doesn't need much... and as for the accuracy... well that is all relative also.

You need to LEARN what the engine's baselines are that are INDICATED on this guage and use them as a reference point. Then if and when there is a variance... that would be the time to worry or do something. That's why IDIOT LIGHTS have some value...

Try and have more fun WATCHING the road... HA!
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Agree 100% Tony. There may have been advances in oil technology over the years that have caused us to have to update our thinking about oil itself, but that old 10 pound per 1000 RPM rule still works great. AFAIC, oil pressure at idle is pretty much irrelevant, as long as you've got some. :)

I think most oil lights are set to come on around (or below) 10 psi, which is fine at idle when the bearing loads are lower. But you still want 80 psi at 8k RPM. And I agree 100+% about their usefulness-- I'm installing really bright idiot lights myself 'cause I can't be staring at the gauge and the exit of the corner at the same time.

From an engine builder's perspective, what has been left out of this discussion is the internal engine clearances, which are most important when discussing oil pressure/viscosities.

For whoever asked about the use of diesel oil, I suspect Tom is using it because of its higher ZDDP content. At least that's why I use Rotella T Synthetic (rated for diesel and gas engines alike) in my own cars. Not familiar with that blend of Redline but I expect it's great stuff and the viscosity range is excellent for summer use, although you'd sure wanna carefully warm the engine (or use lighter oil) if you run your car in the cooler months.

Tony, that's the second time in as many weeks that I've read one of your posts and nodded along in total agreement (I think the other was about carbs). Sheesh, I must be getting old. And "thrifty". ;-)

Cheers,

///Mike
(who uses Rotella T Synthetic 'cause he's too cheap to buy Redline)
 
Nice gauges :grin:

Does the AEM OP sensor fit, or was an adaptor required?

15.3 is too lean for idle, does it fluctuate from 14.7 to 15.3?
 
When it's running that lean, the oil pressure sucks too!

LOL That was just the gauges getting powered up. The O2 sensor was just sitting out in open air at the time.

As for the OP gauge, I used the oil pressure doubler from Midwest-Bayless so that the "idiot" light would also work. I also had to buy an adapter for the AEM sensor to fit the doubler. I also had to put in an extension for the OP wiring harness. The one that came with it was way too short to reach the engine in the rear. AEM said there shouldn't be any problems with the extension as long as I made good connections. So far, everything is working great. The car is QUICK!
 
HA! Hey ///Mike... better end it all now...

... before you get any WORSE! HAHAHA!

But there is SOME light at the end of the tunnel... When yur on Social Security like me you'll then be able to afford Redline!
 
Ya know Tom... there is supposed ta be an...

... idle-speed switch that activates when the A/C is turned on to up your idle. I've seen it on drawings, but never worked on one in SoCal...

('Cause its too HOT here I guess to have an X with A/C! HA!)
 
Dual carb setup, no kickdown for A/C

When I put dual 40s on it, it lost all that stuff. It's something I'll have to rig up later. Some kind of solenoid that holds the throttle open a little when the A/C comes on. Or maybe something with the timing advance at idle.
 
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Redline 15w40 diesel oil

Mike has it right. I'm using the Redline oil because of the high ZDDP content and all the other good stuff in there. Yea, it's expensive, but it's suppose to be really good stuff. I was buying the MT-90 for the trans anyway, so I thought I would just stick with all Redline products.
 
Oh wow... I forgot about your carb set up...

Ya know Tom... yur really a hypercrite here... A/C AND A PERFORMANCE INTAKE...

A REAL man would choose ONE or the OTHER, not BOTH!

I'd be happy to take EITHER one you choose to discard!

HA!

BTW, I have never seen an advance mechanism... usually a solenoid activated device that causes the throttle stop to be altered and lift the idle 200 - 500 rpm.
 
I was thinking

With the dual carbs, I'm no longer using the vacuum advance. I thought I might be able to use the carb style A/C vacuum pull for the vacuum advance on the dizzy. I quickly rejected that idea because it wouldn't be only at idle. The advance would be maintained throughout the rpm range and throw everything off (I think). I still need to get the A/C to function properly first. It's got a couple of issues that I've run out of time to trace down before FFO. I've had to divert my time to waxing and polishing. :sun:
 
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