Oil pressure issue on 365......UPDATE

[txturbo]

1956 365. Looks to be a rebuilt motor, but I suspect it has little to none in the oil pressure department. Will confirm tonight when I get off work. Is this issue common on these motors or is there some common trouble area on these motors I should check into up front ?

[walt chomosh #23510]

txturbo,
  The rocker arms under the valve covers are the last mechanical part in the motor to get oil,and if pressure is low(or if the motor is 1quart low),it will tell you!(clicking) I rebuilt my 1955 331 and have never been pleased with my OP. With straight 30W on a hot day,it will drop near 5psi. Motor will still be quiet though. I bought a oil pump kit(gears and relief spring) and it didn't seem to help much,if any.....walt...tulsa,ok

[txturbo]

Thanks Walt. I don't expect it to have pressure like a modern motor. 5 to 10 psi would be fine at idle. I have run it several different times now and would expect the lifters to have quieted down by now. Going to pull the valve covers this afternoon and see if any oil has been to the top. Also going to hook up a gauge and see what I get.

[Dave Shepherd]

Oil pressure is always a function of internal clearances, cam bearings are overlooked and many times they are not replaced when rebuilding. Makes sure to use a known accurate gage when checking press.

[txturbo]

Motor is real clean inside but under the valve covers it's dry. I'm spinning the oil pump shaft and oil is being pumped up to the area around the distributor drive gear on the cam. If I keep spinning the pump that whole area fills with oil to the point it almost comes out the distributor hole.something has to be missing in there.All the oil is coming out somewhere in there and never going any farther. I'm trying to make out the lubrication diagram in this copy of the service manual but it's to fuzzy to make out details.

[txturbo]

Removed the plug at the back of the motor that plugs off the end of the vertical oil passage. My gauge just barely shows a few pounds of pressure but after spinning it for a couple minutes I have a little oil coming out around the left rear end of the rocker shaft. Then my battery went dead on the drill. I need to find my electric drill and just let it spin for awhile. At this rate it will take 30 minutes to fill up the whole system. Does the distributor block off a passage or something when it's installed?

[curly]

The rocker shafts have to be correctly installed to allow oil to flow into the rocker shafts itself.  If the engine is real clean up top, could it be because someone did some work and installed the rocker shafts on the wrong side?  There are index marks on the front end of each shaft, viewed from the front of the engine, the right (passenger) side mark is at 4 o'clock and the left is at 8.  The marks are 'v' shaped indents on the front of the shaft.

T Lewis

[txturbo]

Thanks.....I'll check that out.

[Jay Friedman]

After a valve job a few years ago my '49 331 showed lower oil pressure than before the valve job.  It was at about 25 psi when running at 40 mph and 5 psi or even less when idling after warming up.  Before the valve job it was 35 psi at 30 mph and about 10 at idle.  To make a long story short, I eventually discovered that one of the rocker arm stands (what Cadillac calls a bracket) had cracked, causing a leak of oil from the interior of the rocker arm shaft and the drop in pressure.  I took the rocker arm assembly apart, replaced the bracket and the oil pressure went back to normal. 

Other rocker arm problems causing poor top end oil circulation and lower oil pressure I've encountered over the years are:

1. Dirt and gunk clogging up the lubrication holes in the rocker arms, which is relatively easy to deal with.  Take the rocker arm assemblies completely apart.  (I suggest one at a time, so you can use the assembled one as a guide to put back together the one you take apart.)  Each rocker arm has small holes through it for oil circulation at the round part which mounts on the shaft and at the end where the push rod seats .  If these are clogged,  a good tool of just the right diameter to clean them out is a straightened out paper clip. 

2. Dirt and gunk clogging up the interior of the shaft.  This is harder to clean unless you remove the plugs at either end of the shaft, but I've always been concerned that I wouldn't find a new plug and that the old one wouldn't stay in place after putting it back.  The easiest solution is to buy a new shaft from Terrill Machine in TX for $38.  A cheaper solution is to soak the arm in WD 40 or other solvent for a day or two, then push a small chain into the interior and shake the whole thing till the dirt comes out the holes.
 

[txturbo]

Thanks Jay. I may have this problem also, but I also have some other reason for low oil pressure before it even gets to the top end. I hooked my gauge where the pipe plug is on the back of the motor. I don't even have 5 psi there because I'm losing pressure somewhere between the oil pump and the top of the block in the vertical oil passage. There has to be a missing plug or a crack that is allowing the oil to gush out near the rear of the cam. I may have to pull the intake and valley pan to see what's happening in that area.
Does anyone have a clear pic/scan of the oiling diagram from the service manual?

[Coupe Deville]

I think I have a lubrication diagram of the 56 365. Will check my 56 book later today and let you know.

-Gavin

[txturbo]

Thanks Gavin. I found one today but it wasn't anymore helpful. Since my last post I have done a little more work. This a pic looking down into the distributor hole with the cam on the left and the oil pump shaft at the top. I think that hole in the center is a drain back hole and the one on the bottom right is the hole that gushes oil when I spin the pump. Does anyone know if that hole is suppose to be plugged or does something connect to it?

[J. Gomez]

Dan,

The small hole should be for the cam shaft bearing/distributor gear lubrication lube diagram attached.

Good luck..!

[txturbo]

Stopped by a machine shop on the way home yesterday and grabbed an assortment of plug sizes. 7/16 is to small, 9/16 is to big so I went with the 1/2" one. The guy at the machine shop told me I would never get that plug in without pulling the motor. I made a tool and it went right in. I out the cordless drill in the pump shaft and spun it up and I'm now getting 35 psi on the gauge.... But I'm getting some leakage from around the plug. Tonight I'll try a couple of ideas to try and stop the leakage and put the distributor back in. We will find out if the plug stays in during the cam break in. There is room to put another plug in there. I may do that also....two plugs have got to be better than just one.

[txturbo]

Couldn't get a second plug to stay in. So I put it back together and now it seems I have too much oil pressure. When I first start it it has 20 lbs at idle and it drops to about 10-12 when it heats up. That's fine....but if I rev it I get insane pressures. On one rev I pegged my oil pressure gauge and the maximum reading is 100psi. So I guess that's better but still not right. It should be ok for now since it will be another month or so before it can even leave the driveway.

[Jay Friedman]

It sounds like the oil pressure regulator valve in the oil pump is not working.  This valve, which is a piston and spring inside a cylinder, prevents excessive pressure by bleeding off oil over a certain number of rpms.  As the pressure builds up, it presses the piston against the spring, the piston moves up to a point where it uncovers a hole in the side of the cylinder and some oil flows back into the oil pan rather than into the oil galleries.

One possibility is that if there is gunk and dirt in the pump the piston can't move, so is stuck in the down position.  Another possibility is that if you bought a kit to rebuild the pump, the replacement spring provided by the vendor is too stiff and, again, doesn't allow the piston to move up enough.

To fix it, you'll have to take off the pan and remove the oil pump.  It's fairly easy to take apart the pump, clean it out and free up the piston.  If the problem is that a replacement spring is too stiff, re-install the original spring.

[txturbo]

That's what I was thinking also. The motor was rebuilt back in the late 90s before I got it, installed but run very little. I'm waiting to see if the transmission is going to work or not before I go any further with the oil pump. No need to waste time pulling the oil pan in the car if the transmission needs rebuilding. Might as well pull them out together if needed.

[Wayne Womble 12210]

Thanks Gavin. I found one today but it wasn't anymore helpful. Since my last post I have done a little more work. This a pic looking down into the distributor hole with the cam on the left and the oil pump shaft at the top. I think that hole in the center is a drain back hole and the one on the bottom right is the hole that gushes oil when I spin the pump. Does anyone know if that hole is suppose to be plugged or does something connect to it?

I always qualify my answers by saying , I have no specific knowledge of later Cadillacs, but i do have experience in other lines. This is no exception, and it may not be relevant in this case, but, in Chevy engines this feed hole uses the distributor case to redirect the oil flow to the upper part of the engine. If it is not installed, there is no oil to the top end. So when you spin the pump without the shaft installed, you get no oil to the top, you just see it gushing out the hole. If you stop this hole with a plug, the pressure would skyrocket, but you will still not get any oil to the top.

[txturbo]

I looked at that possibility and could see no way the distributor housing could do that. I had a dead cylinder and pulled a valve cover to check the top end for oil and bent push rods and I can see I'm getting oil to the top end and that I need one push rod.