The Stovebolt Site Forums The Shop Area Engine Shop 216 oil Pressure Mystery

I am pulling the 216 on my 1951 1 Ton to do a rebuild. When I put the truck on the road ten years and 40K miles ago, I did an in place rebuild. At the time I didn't have the space to pull the motor but now I do. Over the years I have replaced the main bearings and the cracked head. The motor has worn cylinders but runs well. One of the cylinders has been honed out some by a previous owner and so there is some piston slap in that cylinder. I plan to have the block bored and tanked. I will be putting aluminum pistons in it.

Now here is my mystery. Right from the start the oil pressure reading was nearly pegged when cold or at least well over half scale. After about twenty minutes of driving it will read 7 lbs on the highway and around zero at idle. I have replaced the oil pump and the oil distribution valve. The feed to the rockers has the proper restriction. When I replaced the main bearings I shimmed them so the clearance was at minimum and this made no difference in the pressure. The only thing that I haven't attended to is the camshaft bearings. So when I have it apart I will be looking to see if there is a cause of this low oil pressure.

As a contrast the oil pressure in my 1938 Master 216 has always been excellent. Even when the main bearings were really sloppy after I bought it, the oil pressure was excellent.

Truckernix said "I have replaced the oil pump" in reference to work performed on his 216 engine.

I'm still in the novice phase of building a 216 knowledge base. Which likely explains my curiosity with comment above. I've seen the rod dippers and squiters in the oil pan on my truck, I thought that was the source of the engines pressurized oil.

moparguy,
the 216 had an oil pump that fed oil directly to the main bearings and the camshaft bearings. There was also a feed to the "oil distributor valve" which opened after the pressure built up and it fed both those rod sprayers and the rocker arm.

The 48 216 in my 3100 gives around 14psi cold and drops to around 6 or 7psi warm. At idle it's around 6psi and at speed around 7psi. I run 15w40 oil.
I'm guessing your mains are less than 0.003" clearance? If so it's definitely possible the cam bearings are worn. Did the new oil pump make any difference? You might try testing the pressure with a another oil pressure gauge to verify the pressure.

moparguy, the 216 and early 235's have pressurized oil to the crankshaft main bearings, cam bearings, front timing gears, dipper nozells and the valve train. The dippers on the rods provide lube oil for the rod bearings and the subsequent oil mist lubes the cyl walls, pistons, cam lobes, dist shaft and all internal surfaces of the engine.
You might find this video interesting (once it gets past the opening lol).
Riding the film

moparguy,

Your terminology is correct regarding the squirters being pressurized oil (the rod-dippers "accept/receive" the pressurized open-stream oil), but that is the "open pressure" part of the low-pressure lubrication in the 216 (and the same system in the early 235) engine lubrication system. Many people mistakenly call this a splash oil system - it is not.

The "source of the pressurized" oil is the oil pump.

If you have not already done so, read the Engine section of the Shop Manual. Here are some key pages:
http://chevy.oldcarmanualproject.com/shop/1948_51truck/51ctsm0605.htm
http://chevy.oldcarmanualproject.com/shop/1948_51truck/51ctsm0614.htm
http://chevy.oldcarmanualproject.com/shop/1948_51truck/51ctsm0615.htm

Volfandt,
thanks for your response. Yes my mains were set for .001 to ,002. I was very careful because I was trying to get good results from a new rear main seal, and I did. I am thinking my cam bearings are probably quite worn and of course they will be replaced and maybe the cam if it is worn. I am wondering if there are any other places to look for the problem. I actually replaced the oil pump twice and it made no difference. I use the Rotella 15W40 and I understand it still has some good additives in it. I think I will parallel a new oil pressure gauge and see if they agree.

Correction, the 216 in my 3100 is a 49 not 48, must have been a combination brain and finger phart LOL.
Fred, In thinking more on your oil pressure situation, I'm being drawn to the R&R of the oil distributor. The TSM shows it broke down pretty good. When you've pulled the engine and disassembling it, pay attention to how it's assembled. IIRC it's primary job is to limit oil pressure to the top end until sufficient oil pressure is flowing to the mains. Did you replace this due to the pressure situation you're now experiencing?

One other thought, Are you running a by-pass filter? I am and have often thought about taking it out to see if I can gain alittle more oil pressure.

Good luck
Dave

Dave,
I replaced the oil distributor valve with a new one thinking it may be the problem, but no luck. I am running a by-pass filter but things didn't change when I added that.

I think your parallel gauge idea is a good one. May just be getting a bad reading.


You've pretty much eliminated everything but the cam bearings. Good reasoning.

The oil distributor only comes into play when the oil pressure is below 15 PSI if it's working properly. Its function is to direct most or all of the oil flow to the lower end of the engine in hot idle and/or other low oil pressure situations. The rocker arms can survive a lot longer with little or no lubrication, compared to the rod, main, and cam bearings. When the oil pump is supplying sufficient pressure and volume to the rotating assembly, then a little oil can be bled off to keep the rockers lubed. I think the high volume pump modification I'm developing might be the answer to a lot of worn bearing problems on the low pressure engines, if I can ever get back to it!
Jerry

Jerry,
I have often wondered exactly how that little valve reacts. Chevrolet does comment on it in a number of manuals, but the detail is not great. There is a need to keep the dipper troughs full at all times. So I would think the valve has a proportional response to the main pressure. In other words I don't think it is an all or nothing type operation.
Fred

Are you going to use longer gears in the pump or a new gear/rotor design? In the foggy remains of my rapidly dimming mind I recall a tractor or some heavy equipment pump that they used a Blanchard ground and pin located <> 1/2" spacer and longer bolts so longer gears could be used to give more volume. With the whiz-bang kids now they could just make up some 3D printed patterns to make a new mold to give a longer housing---probably quicker than it took me to type it out. A spacer plate could be plasma/laser/water cut quicker than what it would take an old fart to set up a mill. IIRC the gear bores in the housing are just overlapping circles so machining the new spacer wouldn't be complex. I used to love speed, now I'm getting to hate it.

I'll be using small block V8 gears in the stovebolt housing (they're the same diameter) and a surface-ground spacer plate about 1/4" thick to accommodate the longer gears. I'm guesstimating about a 20% increase in volume with a minimal amount of reshaping of the inlet and output tubes. I made the first spacer plate on a lathe with a 4-jaw chuck and turned a pair of overlapping holes at the right center to center spacing, then hand-trimmed the outside shape of the plate to match the shape of the pump housing. Once it's working on the prototype pump I'll use it as a pattern for a reverse-engineered CNC mill program that my son-in-law can write. Then they can be mass-produced as needed. He's a tool room machinist for Remington Arms in Huntsville Alabama.

Fred, from a purely subjective viewpoint, it looks like the spring-loaded disc in the oil distributor is designed to restrict oil flow to the head until there's enough force exerted on its surface area by the oil pump output to push it off its seat and allow some oil flow into the through-block oil line to supply the rockers. As the engine speeds slows and/or the oil thins out due to heat, it will require more pump volume to push the disc off the seat. That will direct more oil to the lower end to protect the bearings. I've seen several references to 15 PSI as the starting point for flow to the head.
Jerry

Can I ask you guys as you seam very knolagable in this area,I can't seam to get an oil supply up to the rockers on my 216 ,I removed the copper pipe and brass fitting from the block from in the push rod area, I start the engine and the oil bearly dribbles out .
i have replaced the oil pump cleaned and blown air everywhere I can to try and clear any oil ways have you any suggestions what I could try next

Unless the engine is running above idle speed and fully warmed up, a dribble is all you're likely to get. The "oil distributor" we're discussing is the roughly triangle-shaped part near the oil pan rail on the carburetor side of the engine. Its function is to restrict oil flow to the top of the engine until sufficient oil flow and pressure is present to assure the connecting rods, main bearings, and cam bearings get lubricated. The copper line that is attached to the oil distributor goes through the water jacket at an angle and ends up under the pushrod cover. You will destroy the line if you try to remove it. Fortunately, there is a replacement kit available if you discover that the line is restricted.

Try disconnecting, or at least loosening the line at the oil distributor and run the engine to see if there is sufficient flow there. You'll probably have to speed the engine up a little to get a good idea if there's enough volume. It's possible the line is restricted with sludge and will have to be replaced.
Jerry

Fokay,
I am assuming that your 216 has the little plate on the driver's side of the block and a small loop of copper tubing that loops out and into the block, just behind the plate. If you removed the front connection of that tube, that is where the oil for the rocker will come from. The plate has a device called the oil distribution valve behind it. That valve is responsible for sending oil to the rocker arm when the oil pressure has built up. There is a small feed hole that goes from under the plate area to that feed. It is quite possible for that hole to become partially blocked. Also expect to see the flow when the RPMs are up high enough to see good pressure on the gauge.