proper oil pressure at idle?

[BarryK]

Hi

I have the 327/365 motor in my '65. While driving the oil pressure usually ranges between 40-60 but at idle while sitting at lights. etc it drops way down to sit below the 20 mark. at times it's barely above the 0 mark. i'd say most of the time it's aprrox around 10.
What should be the proper oil pressure while at idle? Maybe where it's at now is fine but it seems to be awfully low.

 

[allcoupedup]

Barry,
An old racer's rule of thumb is 10lbs for every 1000 RPM. 10LBS at idle is a little low but will not harm the engine. Oil pressure is a function of the pump and crankshaft bearing surface wear. If you're seeing 40-60 at cruising I woudn't sweat it.

The mechanical gauge in the cluster is notorious for being bad. I was getting super low readings and connected a proper test guage and saw about 35 PSI at 3500 RPM. You can easily connect a test gauge at the front of the block - there is an 1/4" NPT (or is it 1/8") fitting right above the timing chain cover. I purchased a nice gauge and hose from Grainger for about $20. Add a few fittings from your local HW store and you have a nice oil pressure gauge.

My new motor with .003 bearing clearance sees 60 at startup and about 40 at cruising with a stock melling m55 pump.

Brian

 

[BarryK]

Hi All

thanks for the info. I figured the pressure at cruising speed was fine but was concerned at the low level at idle. From what you say it sounds about right than so at least that's one less thing on this car to worry about!

 

[Mikey1]

Barry,

I did replace my pump with a stock oilpump because I felt the idle pressure a little to low....

...now it is a little higher....but rule of thumb is still 10lbs per 1000 rpm. Going to cruise speeds it pumps up 40lbs or more.

....same engine 365HP.

 

[BarryK]

thanks Mikey
than since my idle is usually around 800, if the pressure is approx 10 than i'm ok.
that confirms what Allcoupedup said and makes me feel better knowing everything is ok.

 

[Ken Anderson]

10 is way low!

 

[Mikey1]

10 at idle is way low. if you have got something like 15 to 20 I would say you are fine.....adding up some 10lbs per every 1000 rpm.....

...first check the correct oil pressure by adding another instrument (maybe only temporarily..)

....if you really want to be secure I would recommend to change the oil pump. A stock oilpump is only about 40 bucks....

 

[Kid_Again]

...timely post...i just seized my engine because someone i trusted kept telling me that oil pressure below 10 psi at idle was "OK" and i believed him...yeah, right

 

[BarryK]

i've been watching it for the last few days and lately at idle it's closer to 15 or so rather than 10 but I have seen it get VERY low to 10 or maybe slightly below in the past.
As suggested I'll get it checked out - maybe my mechanic has some kind of oil pressure gauge he can check it with.

If a stock oilpump is only about $40 plus whatever labor charged to install it, it's a LOT cheaper than reapiring or replacing the entire motor. I don't even want to consider the replacement option as it's a complete number matching car. Too much to risk and too much value to lose over a $40 part!

 

[Sky65]

Checking with another gauge is definitely a good idea. What weight engine oil are you using? Did you change oil weight or brand?

 

[BarryK]

Checking with another gauge is definitely a good idea. What weight engine oil are you using? Did you change oil weight or brand?

I'm embarrased to say I have no idea on either weight or brand.
Not too long ago I had the valves adjusted and at the same time I told the guy to change my oil and filter while it was there. I have no idea what he put in.
Would the weight really affect the pressure?

 

[Sky65]

I have a 65 sb with a high volume oil pump. It was running 45lbs @ idle hot. I changed the oil from 10/40 to 10/30 same brand. My idle pressure is now 35 hot. I have never verified the calibration of the gauge but both readings are from the same gauge.

 

[BarryK]

Sky, thanks for the info.
I would never have figured the weight would have made a difference

 

[Sky65]

It may not be your issue but if a change occured after the oil change......

 

[Gerry]

Check it with an accurate gauge first and then what is necessary. Low oil pressure will cause $ damage and the fix (new oil pump) is cheap if done early enough. Don't be penny wise and pound foolish.

Bset regards,
Gerry

 

[ctjackster]

Barry, my Oil Pressure is 40 lbs at idle . . . . 800 rpm