OIL PUMP PACKS IT IN?

Posted by Jim L. in OR On 2013/9/17 17:38:55

A week ago last Sunday, I went on a quest to find a brass "cross fitting" for my '51. It being a nice warm day, I took my '55 Patrician for a total of about 27 miles. At the beginning of the drive, the Oil Pressure Gauge read about half way as usual. On the way back into Portland at a speed of about 50 mph, I looked down at the Oil Pressure Gauge and was disturbed to see that the needle sat at about 20 psi. At a stop light I looked again and the gauge read 0 (zero) psi though the engine was still as silent as the tomb and the temp was normal. It was then I realized two things: First, I left my cell phone at home; Secondly, there are no phone booths anywhere anymore. The up shot: There was no calling AAA. Fortunately, I was, by that time, pretty close to home so I gingerly drove there. Once safely in the garage I checked the dipstick. I had changed the oil a few days before and it was still there and a half quart over as usual. I called it a day and went in.

Busy pretty much all last week with the only Packard thing doing was putting the '51 back together. For you fans or irony out there, I then had two running Packards. The first a '51 200 Deluxe that only and always has one of two readings on a mechanical gauge - ZERO when the engine isn't running and 40 psi when it is running - no matter if the engine is turning 300 RPM or 3000 RPM - but sounds like there is a brace of Flamingo Dancers under the hood.
The other being the '55 running lousy oil pressure but dead silent when running.

This last weekend, I decided to look into the problem. First off was replacing the stock Oil Pressure Sender with a mechanical gauge. On cold start up the mechanical gauge needle drifted up to 40 psi and then slowly settled down to about 25 psi. I let the engine run for about 5 minutes then shut it off. I waited about 90 seconds and restarted the engine and got ZERO Pressure! It was like the pump had lost its' prime. Went out the next day (Sunday) and it did a repeat of Saturday's performance. I just got back in from giving it another shot after adding another half quart of oil and this time the gauge read ZERO right from the start. Though all this, the lifters were silent. I left the engine running while keeping my ears open and eventually, the needle lazed it's way to 20 psi.
When I had the car serviced before I began really driving it, the oil pan was dropped and cleaned and the engine flushed with the pan dropping again for a re-clean. This also revealed that the oil pump was not OEM though it was, according to the third owner who knew it's history, "factory" through 1973. I have heard the lifters make noise. The first time was after I woke it from it's 30 year nap and a second time after an oil change though not the last one. In both cases the lifter noise was short lived.

I have said that I intended to switch out the oil pump to an Olds Conversion Assembly when the time came and it certainly looks like that time has arrived. But!

Can anyone clue me in on this one? One thought was that the Oil Pressure Relief Valve is hanging up on something. Like maybe the oil change moved something that is "holding the door open". I realize than the pump being a Mystery Pump makes diagnosis difficult but I am really curious about this little mystery. Especially why an engine design with a known lifter noise problem would be silent with NO oil pressure.

By the way. I realize I'm really pushing my luck by running this engine any more than absolutely necessary so I won't.