1967 Cadillac 429 lost oil pressure

[29tons]

I had the car running 20 minutes oil pressure warm was 30 psi I shut the engine off to hook up timing light I restarted the engine and noticed a lifter was making noise I checked oil pressure it was 0 I quickly shut off engine what happened . The car is a 1967 Cadillac with a 429 engine 

Edited June 1, 2020 by 29tons
To add to description (see edit history)

[MikeC5]

It could be the oil pressure relief valve stuck open.  If the 429 is like the 500, the oil pump is accessible without dropping the oil pan (at least it was on a '76 Eldo I used to own).  

[29tons]

Took the pump apart gears look new relief valve moves freely and I do not see any reason for it to have lost pressure. Even the gasket looked ok.does the oil pump pick up oil through the filter? 

[Ovalrace25]

429 has the oil pump in the aluminum front timing cover. dirty oil can wear out the pump case allowing oil pressure to drop. With long-time oil pressure drop, the cam bearings go bad, lifter noise begins and general engine failure comes along. I have had several Cadillac 429 engines apart to rebuild. 1964 to 1967. ALL of them that failed did so because of oil pressure failure. The worst cases began with incorrectly installed valve cover gaskets. the head design allows oil to build up around the valve covers. If the valve cover has ANY leak at all, the oil loss adds to premature engine failure. I have at least 4 engines here that are for parts only, failed due to oil pressure loss. The 1963 Cad 390 is also in this same scenario. The 49 to 62 Cad engines are the best overhead engines that came out of Cadillac since the 346 flathead!   

[Robert G. Smits]

Did you determine the cause of your oil pressure loss?

[29tons]

no did not figure it out yet. The strange thing is if I run the oil pump with a drill the oil pressure will go up to 35 to 40 psi within 3 seconds of drill turning. but when i put the distributor in the car and start the engine it shows between 0 to 5 psi oil pressure. I am sure The distributor is locked in to the pump because it would not go in the last 1/2 inch and I had to pull the distributor out and turn the pump with a screw driver slightly to get the distributor to drop down.The engine was rebuild 25 years ago but never started so before i started it i pressurized the oil system also put oil down the cylinders and turned it by hand to make sure everything had oil on start up. I recently drained the oil and put new oil and filter in it just in case the oil was diluted with gas but it was not. I had valve covers off I thought maybe oil return holes where clogged but they where not and the engine looks like new inside Some one in an earlier post said that the cam bearings could be bad my thought is if i have oil pressure with a drill it should have pressure when its running. I may pull the pan off next maybe i can see if there is a problem with cam bearings. Please keep replies coming thanks for all the replies.  I am stumped.    

Edited June 16, 2020 by 29tons
wanted to add something (see edit history)

[m-mman]

9 hours ago, 29tons said:

The strange thing is if I run the oil pump with a drill the oil pressure will go up to 35 to 40 psi within 3 seconds of drill turning. but when i put the distributor in the car and start the engine it shows between 0 to 5 psi oil pressure.

 

This is a interesting symptom. A solid rod on a drill reliability makes flow/pressure (as a speed that is lower than a running engine) but the distributor shaft from a running engine does not. . . . ?

 

I am thinking that there is slippage somewhere along the distributor shaft. Examine the "rod(s)" from the distributor drive gear to the oil pump. If the distributor drive gear was slipping (is it pressed on? no pin?) the timing would change and the engine would not run. BUT, if the shaft that transmits the torque from the cam gear to the oil pump were slipping (especially under the high torque of a running engine) then the oil pump would stand still.  A pressed on joint (no set screw or pin?) at the oil pump gears might result in slippage also.

 

Not an expert on Cadillac design, but slippage under torque higher than that produced by a drill, is a place to look. 

[JACK M]

Good thinking m-mman

Quite likely a sheared roll pin or even a press fit on that shaft.

Not being familiar with the specific Cadillac but knowing a fair share of engine basics the problem has to be at that distributor shaft.

Best fix may be another distributor.

 

Twer it me I would put the distributor on the bench and twist on it a bit.

Edited June 17, 2020 by JACK M (see edit history)

[29tons]

I have checked measurement on distributor and oil pump they are engaged by 3/8 of an inch. Also took the plate off the oil pump put my finger on the bottom center of the gear and turned the engine over the gear is turning . Also the drive gear mounted on the bottom of distributor shaft has a roll pin through it if this were slipping the distributor would be out of time quickly and motor would not run. the oil pump shaft fits inside the bottom of that gear. The oil pump drive gear cannot go down due to the plate on the bottom of the oil pump and the distributor cannot go up do to being held in place with the lock at distributor adjustment.I also can see clearly through the roll pin on the distributor drive gear.I put a substantial amount of pressure  on distributor shaft and drive gear it dose not move.

Edited June 18, 2020 by 29tons (see edit history)

[29tons]

The oil pressure problem is fixed.I pulled down the pan checked the oil sump for cracks or clogged screen saw no problems checked sump gasket it was fine. Pulled down a couple bearings they still look like new.Also looked up at cam bearings and tried to rock or move cam but using a dial indicator had only a few thousands of movement. Put the pan back on. I ordered new oil pump gears and relief valve and gasket mainly because you could not by a relief valve separately.   The gasket that came with the kit did not fit the housing properly so I got a victor gasket.Same problem oil pressure with a drill but no oil pressure with distributor in place. I checked the thickness of the gasket that came with oil pump kit it measured .008  Then I checked the thick of the gasket that was in the car when the motor was rebuilt. .028 Then  I checked the victor gasket The area that was not crushed was .031 the crushed part measured .028. So I got gasket Paper at a  Place where I worked that measured .008  Cut it to fit. I took a screwdriver and turned the oil pump with my hand to make sure it was not binding and it turned freely. I turned the pump with a drill the oil pressure came up to 45psi. I stuck the distributor in place and with only a few revolutions the engine had oil pressure. I started the engine ran it for 20 minutes the oil pressure started at 45 Psi and when it was warm it stayed at 30 psi which is what the book says it should be. I left the engine sit for 15 minutes and restarted it the oil pressure went right to 30 psi. The gasket that comes at least with 2 different companys that I tried is  to thick leaving the oil bypass the gears.I noticed when I was holding the drill in place that i was pushing down and that was closeing up the gap at the bottom gears.and allowing the oil to pump.I have started the engine several times now and had oil pressure every time. I noticed several other posts with the same problem so I wanted to tell people what I found.

[JACK M]

Hmm,

I was thinking that this was a running engine all along.

Then it sounds like you had just been working on it.

Now a reread says it was rebuilt 25 years ago and never started.

Regardless, glad you have it figured out.

[m-mman]

On 7/3/2020 at 9:57 AM, 29tons said:

I noticed when I was holding the drill in place that i was pushing down and that was closing up the gap at the bottom gears.and allowing the oil to pump.

 

There had to be something happening different between the drill and the motor. Pushing down. . . who would have thought? 

[29tons]

It was a time consuming brain teaser  for sure.  

[m-mman]

Thick gaskets are rarely an issue.  But another example I experienced is with the Geo Metro 3 cylinder.  Some oil pan gaskets are too thick and can cause the crank position sensor to be too far from the vibration damper for the signal to be sensed.  Symptom?  Change the oil pan gasket and suddenly the engine wont run. . . . . <doh!>