1963 390 no oil pressure

[mark]

I'm hoping that there is someone knows these engines and can help suggest where to look. When I got this car the engine was down to the bare block. So I honed it, put in new rings, new cam & bearings, New main & rod bearings and plastigauged it. Every thing was within specs. After assembly I put it in the car and started it up and noticed there was no oil pressure. Pulled the distributor and used a drill to check from there on. First I removed the oil pump cover and checked the pressure relief piston. There was a small burr in the housing so I cleaned it up and reinstalled. No pressure. The gears were worn so I got new gears, piston and spring from Melling and replaced them. No pressure. Pulled the oil pressure switch and installed a fitting and hose to a bowl. I am getting some flow but not a lot. Removed left rocker arm cover. No oil. Removed timing cover housing and replaced with a good used one. The gear housing and shaft clearances were better. No pressure, some flow. Is there somewhere else the oil can be going? At this point I'm ready to pull the engine and start over. I've built many engines in the past 60 years and never had a problem like this. Any help will be greatly appreciated. Mark. 623-203-9631

[TJ Hopland]

You don't sound real confident in the condition of the housings but it seems like you have general experience and think while the condition isn't great it should be making a lot more pressure than it is.     

Can you drop the oil pan while its in the car?  Careful inspection of the pickup tube and how it attaches?  If that all looks good maybe rig up a plastic tub as a temp oil pan so you can test it again and maybe see if you can see oil flowing from somewhere?  Maybe you will see oil flowing back from one corner and know where to focus? 

[mark]

Thanks TJ for the response. I've had the oil pan off and checked the pickup tube and it's clean and there are no cracks. There weren't any air bubbles in the oil that I got in the bowl when I tested the flow. I had considered doing what you said about pulling the pan and putting a tube in a gallon of oil but I would have to get another tube that I could cut and there would be oil everywhere under the car. I was going to remove the intake and the valley cover and see if I could see where it's going but it's just to much of a hassle trying to reach over the fenders. Not as young as I used to be! So I'm pulling the engine tomorrow. I've already got the starter, crossover pipe, p/s pump, radiator, hoses, etc. removed while I've been working on it so it won't be that bad. I hope! I'll let you know what I find. I was just hoping that an engine guy might have had a similar problem so I wouldn't have to take it out. Not the worst thing in life. Thanks again. Mark

[cadillactim]

How thick is the gasket on the oil pump plate on the bottom of the pump assembly? It needs to be paper thin in order for the pump to build enough pressure.

Some reproduction gaskets are too thick and won't let enough pressure build.

Had this happen when I rebuilt my 67. Put in the correct gasket and then had plenty of pressure.

Tim

[mark]

I thought about the cam bearings. You're not the first that has mentioned this. If one moved forward or back that would cause the problem. If it just turns it might or might not cause the problem. I haven't seen any filings in the oil pan. We'll see. The gasket kits came with two different gaskets  for the oil pump and I used the thin one. It gives me about 2 to 3 thousands clearance. I have checked the clearances with the new gears and it's close - within specs. Thanks for the thoughts. 

[cadman59]

As far as I know the '63 uses a full flow oil filter. Could it be the filter is blocked?

[E Masters]

Not sure about the 390 but the 67 429 has 2 pressure relief valves.

[Jason Edge]

The oil pressure relief valve sticking is the most common reason for loss of oil pressure. A clogged pickup screen in the oil pan can also cause this but usually see a decrease in pressure gradually as debris builds up. I have seen relief valve just stick open on a running car from sludge, etc, but anytime the front engine cover and that oil pump is removed and disassembled it is always always a suspect area when oil pressure drops. With that I have a few questions:

- how did you notice there was no oil pressure? Are you using a gauge, watching oil pump up to the valve train, or just relying on the dummy light that kicks on when less than 7psi? If relying on the dummy light could be a cut wire or bad sending unit. I like to screw a pressure gage into the back of block and watch the pressure. If I remember correctly these are standard 1/4" NPT thread and you can get a gage for about 10 bucks at the hardware store.

- did you prime the pump by putting oil in the filter support bracket per shop manual instructions.

- and most importantly, did you make sure that relief valve (piston) slides freely inside that cylinder?  If there is any debris in there it has to be cleaned out.

[mark]

Thanks for all the suggestions. I primed the pump before I put the filter bracket on and a new filter. If it was plugged it would have high pressure. Oil pickup tube is spotless. After using the pressure light (with a new sending unit) the first couple of times I disconnected the wire and was using an ohm meter for the next three of four times. Then I put in a mechanical gauge for the rest of the time. I've tried another housing that looked better than mine and two pump covers making sure the piston was free and clean. The new gears came with a piston and spring. There is only one relief valve. The hood is off so out comes the engine.

[E Masters]

Maybe as a last resort try a thicker oil making sure the filter has oil in it too.

[dn010]

If you were down to a bare block and at this point after all you've checked off your list of possibilities so far, I'd suspect a blocked oil passage. Perhaps some critter got up and made a nest, I know mud wasps down here in Florida make all sorts of nests in the tiniest of places. Perhaps try going in with some compressed air or oil gallery brushes to see what happens.