Packard Forum Index » V-8 (1955-56)

Hey Tim,

How did you determine that the camshaft bearings were the cause of the oil pressure problem on the DeSoto? While I am still thinking that the mystery oil pump plays at least a role in my situation, I do want to take care of first things first. I would rather not go through what you customer did when the oil pump turned out NOT to be the problem.

Thank you again for all your help in this.

Dear Mark:

Running one quart over is pretty much a good way to operate the Packard V-8 because it submerges the oil pump and reduces foaming.

5 psi at hot idle is pretty much okay depending on what oil you are using. Factory spec is SAE 20w, so 10w-30 is a good choice for a new motor. For an old motor people like 15w-40 which is fine and has more detergency because it is for diesel trucks. Keep in mind too that on modern cars the gauges are computer controlled to minimize customer complaints, the gauges are just decorations. My modern car has lights for everything except temperature and I'd just as soon prefer a hot/cold light for that as well. As long as the MIL is off I really don't care what is going on under the hood. It doesn't have a tach either and I don't care.

Now on to this DeSoto question. If memory serves me correctly it was dropping to 20 psi at 35-45 mph which is low. On a V-8 you can't isolate cam bearings as a cause of low oil pressure, but on flat head inline motors there are plugs in the side of the motor for the camshaft oil holes. In the old days used car dealers used to cure low oil pressure by putting restrictors inside those plugs, and viola!, good oil pressure. Low oil pressure in the absense of motor noise is symptomatic of worn cam bearings. When mains are bad oil pressure is low too, but there is also some motor noise, less so in V-8s but very much so in under square inline motors like Packards.

Oh, and the rule of thumb for required oil pressure is 10 psi per 1000 rpm. So for a worn motor with 30 psi oil pressure at 50 mph the maximum rpm you want to operate at is 3000 so a car like that should be fine on secondary roads but will blow up on the highway. In the old days I remember cases where someone would buy so and so's original Packard and promptly blow it up on the highway whereas as the original owner did very well driving it around town.

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Just to clarify this "rule of thumb." This number (10psi/1000rpm) is OK for a nominal 3.000in main bearing diameter. For a Packard V-8 with 2.500in mains, the number would be ~8.3psi/1000rpm (2.5/3.0). For example, a Pontiac 421/428/455 with 3.250in main bearings, the value is ~11psi (3.250/3.000). The early small block Chebbies had a 2.300in main journal and could get by with 7.6psi/1000rpm.

The reason for this is that the oil pressure has to overcome the centripetal force of the oil in the internal passage from the bearing surface to the centerline of the crankshaft before any oil can reach the rod bearings.

Packard service manual lists the "Normal oil pressure" as 45-50psi at 2800 rpm. Obviously, this is more than enough pressure to overcome the main bearing centripetal back pressure.

The above is probably more than you wanted to know, but I thought I would lay it out here anyway.

Craig

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Craig, I am one who believes that one can never have too much information - if you don't understand all of it then you ask questions or do research until you do. This is especially true when it comes to my Packards!

Oddly enough, at least to me, I do understand what you and Tim are saying and I find it a little reassuring. One question I do have: Does 3,000 rpm translate out to about 55-60 mph on a '55 Patrician with (I suppose) standard rear axle ratio?

My thanks to you and Tim for allaying some of my fears. For to be honest the prospect of staying out of my '55 after waiting 56 years would be harder than quitting smoking. For those who don't smoke or have never tried to quit that means Damn Near Impossible!

Since school is out for the year it occurs to me that if my Packard were receiving grades, on the subject of Oil Pressure: The best it could hope for is a "Gentlemen's 'C'".

Again, my thanks to the two of you as well as Randy, Rowdy, Jack, and everyone else who has chipped in ideas. Any more ideas a certainly welcome.

My God, I almost forgot Howard - to whom I am so deeply in debt as to never get out.

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3000rpm on my 55 Pat with 3.54:1 (stock) rear axle ratio and 28in diameter tires comes out to about 70mph. See this handy calculator for other values:

http://www.wallaceracing.com/calcmph.php

Craig

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Craig: Thank you so very much for the RPM - Speed Calculator. My Speedometer went into the shop work and came out not. One of the items on a short list of fixes. With your calculator I can pretty well guesstimate the RPM my engine is turning by knowing what the usual speed of traffic is on what has become my own edition of the Packard Proving Grounds.

As I posted yesterday, I added a quart of oil to the crank case (the dipstick showed FULL before I added the oil). I took it out afterward and received so-so results.

Today, with a cold engine, I ran the route again with quite different results. Oil pressure was well with spec on the outward leg on the freeway travelling at 55-60 to match traffic flow. The outward leg isn't where the problem truly showed. When I pulled into a parking spot the oil pressure read 12 psi in gear - which it hadn't done before. After doing a little more shopping (about half an hour as the store was packed) I got in for the home stretch. The starting pressure was 15 psi and rose to between 20 to 25 as I turned onto the main street. Throwing caution to the wind, I decided to take the freeway back. pressure at 55 or so was between 40-45 psi. Emboldened by these never before seen numbers at that speed with the engine at operating temperature, I blew past my exit and moved out a head of the traffic going 65 - 70 mph. Looking down, the pressure was between 50-55 psi. Finally coming to a stop (in gear) in my driveway, pressure was a shade less than 10 psi.

Now, I'm not going to claim that the addition of the extra quart solved all my problems, but the numbers are a heck of a lot better than I've ever seen before. Through it all, the engine ran very quiet and when leaving all the other traffic behind, the engine and the rest of the car seemed eager for more.

Needless to say, there will be more testing in the coming days and I still plan on going to the Olds Conversion pump simply because I'm leary of what's lurking down there.

My thanks to you, Craig, as well as Howard, Tim, Randy, Rowdy, Jack and any one else I have left out.

More news as it becomes available.

One more thing. On the way back home I noticed that the clock had started working. If my here to fore silent radio suddenly starts belting out Little Richard tunes I'll begin to think I've bought Christeen's older and richer cousin!

Sorry, I didn't read back thru the entire thread so let me ask, have you dropped the pan, cleaned it, and checked for an accumulation of sludge choking off the pump inlet screen? I always recommend doing this on any new old car acquisition when you don't know that it's been done recently, and when I did it on my 56 I was astounded by the accumulated to crap that had nearly closed off the screen.

If and when u drop the oil pan besure to save any of the little solid pieces. Look for solid black kind of plastic hard pieces about 1/2 the size of a small finger nail. THose will be valve seal fragments. THose fragments are lite enuf to suck into the screen and plug it up. That's what i found in mine as well as two other Packard V8 engines. Either way, save any solid pieces and we'll analyze from there.

I'll begin to think I've bought Christeen's older and richer cousin!
I had my 56 radio repaired and picked it up on a Sunday. Son and I drove home and he suggested hooking it up and listening to it. I hooked up the antenna on the van and ran some jumpers to the radio. I turned it on and it began to hum. My son said it didn't work - I told him to be patient - the tubes had to warm up.
The first thing from the speaker was "Who knows what evil lurks in the hearts of men?"
I damn near dropped the radio. Sunday evening radio was broadcasting old radio shows. Gave me quite a start.

Randy Berger Quote:

Randy: That is a funny (weird) story! That would freak out anyone. LOL Thanks for telling it.

Craig