Packard Forum Index » Post-War (1946-54)

Hi Folks,

Just wondering if anyone has, or has ever, hooked up a mechanical oil pressure gauge to right where the oil goes into the lifter gallery in a postwar 288/327/359 with hydraulic lifters. If so, what kind of readings do you get? Especially interested in the reading at idle after the car is well warmed up, e.g. after 45 minutes of driving. Service letters indicate that the oil pressure light might "flicker" in these situations. What oil pressure would that correspond to?

Thanks in advance.

J

For what makes the gauge flicker, I think it's about 10 PSI, though the gauges and signaling were all but precise. The service manual IIRC says that 10-15 PSI at idle is expected, and I don't believe that to be inaccurate.

On my V8 it's about 12 PSI at warm idle, reading from a mechanical gauge.

The sender is at the oil feed from the camshaft to the valve train so there will be little difference. The earlier cars had the feed at the camshaft oil gallery but moved it across the block when they went to an electric sender.

And the flickering also depends on the pressure rating and sensitivity of the switch installed. No idea what Packard specs were for the factory used switch but would be nice to know if anyone has documentation with that information.

The aftermarket replacements for inline 8s are hit or miss spec wise so I don't really trust what they say is factory correct. One parts store offers a switch that has a nominal rating of 6 psi but looking at the switch spec it has a fairly wide range of 3-8.3 psi where it will operate. Another replacement switch that a different store had as correct a few years ago gave a nominal rating of 12 psi but with a range of approximately 10-15 psi.

The switch that will close if it falls below the lower pressure will not flicker as much as one that closes below the higher pressure. Tradeoff comes with what safety margin you are comfortable with. The options are one that might flicker a lot but gives a solid warning if pressure drops below approx 10 psi or one that does not flicker at all but also might not signal a problem until the pressure drops below 3 psi which IMO, is quite low. Downside to one that flickers a lot is you get used to it and might tend to ignore a real issue and one that will only signal at a very low pressure might have already had damage done.

The sender for the light, at least on my car, is at the junction block where some of the oil goes to the oil filter, and some to the oil line that leads to the lifter galleries. What the sender is reading is before that split, though granted there should be little difference between the pressure there and the pressure as the oil goes into the lifter gallery.

This service counselor says the pressure should be no less than 5 psi at idle (10 MOH). Anyhow, just wondering if anyone has actually measured it with a mechanical gauge while running, e.g. in lieu of or in addition to the pressure switch for the light.

Service Counselor, Vol 27, No. 11, "Noisy Hydraulic Tappets"

The general rule is 3-7 psi for the light which translates to 5 psi for 500 rpm given required 10 psi oil pressure per 1000 rpm. Packard always specified rather low idle speeds so a flickering light is not always indicative of a problem. Somewhere in the literature is a note about that.

The note about the loose oil pick up tube is worthy of note. I have run into that problem and don't have a high opinion of that set up. The earlier cars with the fixed pick up and bolted tubes did not have oil pressure problems like those later engines.

There is this STB, which I believe is applicable to all 1951-54 288/327/359 with an oil filter.

STB 50T-52, oil pressure light on/flickering at idle is normal

This is exactly the situation I was experiencing:

"Even though the light may flicker or light up at idle the oil pressure is adequate".

I wonder how many Packard owners were happy about that situation!

What I did was to install a Parker C-Series brass check-valve with a crack-opening pressure of 10 psi in the line to the oil filter. Then when the pressure is < 10 psi all the flow goes to the lifter galleries. The light doesn't flicker any more, but when running at speed, oil still goes to the filter.

The check valve seems like a pretty good idea.

Chris