The Stovebolt Site Forums The Shop Area Engine Shop 216 oil pressure

For some time, I've been tinkering with stovebolt oil pumps, trying to figure out how to solve the problem of low oil pressure that seems to be a chronic problem with 216 engines, particularly ones with a few miles on them. The 216 presents a unique set of circumstances, since the connecting rods aren't oiled by passages drilled in the crankshaft. Streams of oil are squirted across the block just below the crankshaft, and dippers on the rods intersect the stream at the bottom of the piston travel when there's a minimum amount of load on the Babbit bearings. At idle, the rods are lubed by dipping into troughs that are filled by the squirt tubes. The clearance of the rods has nothing to do with maintaining oil pressure. The oil pump is tasked with lubricating the main bearings, the camshaft, timing gears, and the upper end of the engine- - - -rocker arms, etc. An "oil distributor" prevents any oil from going to the top end unless there's at least 15 pounds of pressure to the crankshaft. That's probably why worn rocker arms and shafts are found pretty frequently, and why the top end of some 216's looks pretty dry - - - -not enough pressure to open the oil distributor valve.

A 216 oil pump is a tiny thing, with very short gears. The full-pressure 235's use a similar pump, but the gears are about 1/4" taller than the 216 has. The most popular 235 replacement pump is the Melling M-45. I've found that with a little creative machining, the M-45 gears can be fitted to a 216 pump housing. The gears are the same diameter, but a spacer about 1/4" tall needs to be fabricated to take up the extra distance between the pump housing and the base plate when using the taller gears. Slightly different plumbing might also need to be done due to the height difference. There are other modifications, but nothing that a well-qualified machinist can't handle. The modified pump should flow about 20% more oil, with a corresponding rise in pressure.

Moving on to the 235- - - -a Melling M-55 pump for a small block V8 has gears about 1/4" taller than a 235- - - -once again- - - -the gears are the same diameter and pitch, and fit the 235 housing. A spacer and a new driven gear pivot shaft needs to be fabricated, the same as with the modified 216 pump. The output volume increase should be similar with the bigger gears in the 235 pump.

Then there's the final step- - - -I'm just about to see if there's a way to build a fixture that will allow a complete small block V8 pump to be bolted onto either a 216 or a 235, and be driven by the bottom of the distributor shaft. That would require a little creative plumbing and some test-fitting to be sure there's adequate room between the side of the oil pan and the crankshaft, but I think I've got the drive system just about planned out on paper before I start whittling on steel! More to come!
Jerry

Jerry (Hotrod Lincoln) : you have very well thought out and consistent reasoning in your premise !
Now....as a newbie here, please let me say I truly have a respect for your knowledge about these old stove bolts, and I am by no means an expert on them ....
but, well I think I might politely wonder on whether a stock 216 (or a stock hi-torque 235) needs a bigger oil pump output (in terms of gallons perminute) than what was provided by GM as stock. I think the spec stock pump was well overrated for fluid pumping capacity, so much that it needed a blow-off plug&spring for times of excess pressure (>40-65psi)

Would you agree that those 216 & hi-torque 235's with the combined (aka 4-way) engine lubricated systems are NOT true low pressure (psi) engines, but instead relatively hi-flow (gpm) in lubricating oil?
Would you also agree that the oil pressure we read on our gauge is a major product of engine rpm and oil viscosity ?

The problem with 216's with a little wear is that the oil pressure gets so low that the upper end parts don't get lubed. Every time the oil lubricates a part such as a main bearing, cam bearing, etc., a little oil leaks away. That leaves a bit less volume to lube subsequent parts down the line. There needs to be sufficient volume to get to the end of the line, so to speak. Oil pressure builds up when there's more volume than the bearings and other pressure-lubed parts require. It's theoretically possible to get adequate lubrication with zero oil pressure, as long as the last item in the circuit receives enough oil, just as the pressure disappears. In practical terms, a minimum pressure of 20 PSI or a little more is needed with the engine at normal operating temperature to assure there's enough reserve volume for consistent lubrication of all the parts. Most tired 216's can't manage that feat, and a little more pump volume will remedy the problem. All oil pumps that I'm aware of have relief valves- - - -they're there to prevent mechanical damage when the oil is cold and thick.

A bit of trivia- - - -when the small block Chevy V8's started getting enough miles on them to need overhauling in the late 1950's, a "normal" in-the-frame overhaul consisting of rings, rod bearings, and a valve job didn't work well- - - -the oil pressure warning light would flicker at hot idle, particularly on automatic transmission cars. That pressure light switch turned on at 7 PSI. The culprit was excessive oil leakage at the cam bearings, resulting in idle oil pressure low enough to trigger the low pressure light. Dad stopped doing in the frame rebuilds after that because high-volume oil pumps for small block V8 engines hadn't been invented yet. That happened about 20 years later!
Jerry

Jerry: I think I see what your saying , but that 216 oil circuit is far from a closed loop. It is by nature 2 main branches and the oil pressure gauge only does a moderate job of showing psi in one branch of the circuit.

In the 1950's garages sold a little plunger-like tool to ram pressure up the 216 oil tube to the head to try and unclog dirt and sludge from that line.That engine plaque is what aided in starving those rockers. Wouldn't increasing oil pump volume just cause more blowby elsewhere if the clog would not come loose?
That stock pump on a stock 216 is well balanced to provide just right flow to vital parts. It's not low pressure as it reads on the gauge, its just right.
Are you saying that if the main bearings and cam bearings are worn so much that the oil psi reading is low, then a higher capacity pump will cure that wear?
Will that hi-capacity pump need a different oil distribution valve and setting?
What effect will the increase in capacity have on the flow from the target nozzles in the oil pan?

Arguing semantics with you is getting a little boring. More oil volume doesn't fix anything- - - -it just gives the valve train a little better chance of surviving when the pressure to the oil distributor drops below the level needed to route the oil to the top. I used those ram jacks back in the 50's to temporarily de-sludge oil passages. Using one involved removing one head bolt and filling the hole with motor oil, then smacking the top of the dowel with a BFH. A whittled-down broomstick would do the same job if a guy was too cheap to buy the tool off the Snap-On truck.
Jerry

Jerry,
I am genuinely sorry that you find my conversation with you a boring argument in semantics.
I honestly found that you were pursuing an interesting path, and since I worked R&D at GM many years ago, I didn't think that path was booring, nor a matter of semantics.
I'll leave this thread now as I truly meant not to offend.
Mea culpa....

Some things never change in the automotive industry. Chevy, and GM in general, builds parts to the lowest common denominator. It would have been possible to design just a bit more capacity into their oil pumps instead of making parts that would barely get a vehicle through the warranty period, but it would have been rejected by the bean counters. The deficiencies of the 265 V8, oil-wise demonstrated the same lack of concern for longevity that the 216's inadequate pump had years earlier. Fast forward 50-sdomething years, and the downsized 100 amp alternator used on the late-1980's GM vehicles with the too-small Torrington roller bearing in the back- - - -the one that resulted in locked-up alternators and the occasional underhood fire that totaled vehicles speaks volumes about the ongoing obsession with using parts that are barely adequate.

When my brother was doing computer modeling of parts for GM, Ford, and a few other car manufacturers in the early 2000's, where he would design a part on a computer, then simulate running it to failure to predict its lifespan, he encountered the same obsession- - - - -"How cheap can we get away with making it?" Some things never change. Do I need to mention the Corvair engines that leaked oil from brand new cars on the dealership showroom floor, or the Vega, with its high-silicon aluminum cylinder walls and pistons plated with cast iron? Honing a cylinder and replacing a piston on one of those engines was impossible, because there was no way to acid-etch the aluminum away from the silicon in a dealer's shop. The block had to be bored for flanged sleeves and conventional aluminum pistons installed. I made a good bit of pocket change machining those blocks after dealers wanted their customers to pay for complete replacement engines on out-of-warranty cars .

The oldtime mechanics I grew up around in the 50's had a saying that I learned to appreciate- - - - -"Fords break- - - - -Chevvies wear out!"
Jerry

Hey Hotrod. Gonna bump this thread up hopefully you're still active. I'm dealing with a 216 out of a 49 3/4 ton pickup and cannot seem to find or figure out the oil distributor and how it works.
We've got no oil pumping out of the top (rockers) despite all lines being clear. Oil pump seems to push good and visually looks fantastic considering age.

I'm stuck on how the distributor valve works. Is it replaceable? Doesn't look like it is. With the pan down and an electric dril on the oil pump, it just seems like all the oil is dumping back out the tube that goes into the rod 'dipper' trough's, rather than going up to the rockers, essentially I think it is 'bleeding' off the volume so not enough pressure is going up top.

Would love any advice you could offer or explaination to help us figure out this distributor... So far your explaination and posts here are the only things I've found that make any sense to function!!! The other stuff I've read all seems to say distributor doensn't allow oil into the rod-dipper troughs until the top end sees good pressure.... which seems to be the opposite of what we have going on.

Nope, that's backwards- - - -the oil distributor restricts the oil flow to the rocker arms until there's at least 15 PSI in the lower end. That's intended to sacrifice the rocker arm shaft if necessary in order to keep the crankshaft and camshaft lubed. The oil distributor is a 2-section item consisting of an inner piece with a spring-loaded valve and an outer cover that bolts on over it. It's located on the outside of the engine block on the driver's side, near the oil pan rail close to the exhaust pipe, and it has a roughly triangular sheet metal cover. The line that enters the block beside it goes to the pushrod cover on the other side of the engine, passing through the water jacket. That's how the rocker arms get their oil. At idle (or spinning the oil pump with a drill motor) there probably won't be enough pump volume to push the distributor valve open and lube the top end. Fortunately, at cruise speed, the pump will deliver more volume (and pressure, hopefully) and push a little oil to the top end. As the main and cam bearings wear, they have more clearance and require more oil volume, which can seriously reduce the oil flow to the cylinder head.

Another possibility is that the copper line that transits the water jacket diagonally to supply oil from the distributor valve to the pushrod valley can get clogged or broken. I've seen those lines break under the pushrod cover and just dump the oil back into the pan instead of lubing the rockers. Try disconnecting the line at both ends, at the center of the rocker arm shaft and down by the oil distributor, and give the line a good shot of carburetor cleaner and some air pressure. If it's in one piece, that might clean it up. The line can be replaced, but you'll need to drain the cooling system first. Removing the line destroys it, so have a replacement kit on hand before trying to take it out.
Some of the resto-ripoff places have a kit to replace that line and its associated fittings. It's made of 3/16" OD copper tubing and that's a little hard to find, along with the fittings needed to replace it. DON'T use 3/16" steel brake line- - - -it will rust out and let coolant get into the crankcase and oil into the radiator!
Jerry

When I reworked my oil lines, I went to a refrigeration supply house and picked up the copper tubing there. Trade name is cap (capulary) tube.
Jim

Capillary tubing is used in some refrigerators and other cooling devices instead of an expansion valve or other type of flow control device for the refrigerant gas. Be sure it's not the type with a very tiny pinhole inside instead of a full-diameter tube with about .015" wall thickness. 3/16" copper tube is also available in short lengths on Ebay. It takes about 3 feet of tubing to make the run through the water jacket and up to the rocker arm oil connector, and some special-design brass compression fittings are also needed to seal the tube at both sides of the water jacket.
Jerry

I'll vie for this kit . It was complete with everything needed to replace the line from the oil distributor to the rocker shaft center section except the side pan gasket, valve cover gasket and someone to do it for you.....

Good luck
Dave

Yep, and it's also got those hard to find compression nuts that crimp down on the tubing the first time they're tightened. That makes the tube a one-time installation. Do it right the first time or start over with a new kit.
Jerry

Hello, olddog here, back with another question, I now have a Six Cylinder Chevy engine with serial # on pad beside distributor, # stamped on pad,
92227
KAAI6I705. Stamped as shown on pad. Can anyone help with this engine number? Again thank you for any knowledge shared.
Olddog.

According to this site:
http://chevy.oldcarmanualproject.com/models/engine.htm

KAA is a 216 from a 1952 passenger car. Does it have a pushrod cover that also overlaps the cylinder head, and a sheet metal oil distributor cover near the oil pan rail on the driver's side? You might also want to look at the casting number on the block.
Jerry

Amazing and detailed replies. Thank you!!
I put a gauge on it, and at top speed on the drill most I can get is 12 PSI. Oil just starting to barely dribble into the rocker shaft and out of the return pipe in the supply tube on the rocker. Coincides with your saying valve is opened at 15 PSI. Based on what I'm seeing I'd imagine it starts to open around 8 PSI and is maybe fully open at 15PSI? Though currently there's variables/unknowns to that guesstimate haha .
Ran the truck with valve cover off and got the same result. Once warmed up the gauge fluctuates a little with a slow dip to about 3 PSI then back to 10-12.
running at fairly high idle (no load) pressure doesn't really increase much. This is with 20w50 dino oil.

I think I'll remove and inspect/replace the distributor valve next, though based on what I've read and now know it seems like 10-12 PSI isn't bad at all for this old girl. have to wonder if replacing the line is going to make a lick of difference.
And we did spray and clean the tube out, though I'm sure doing it a few times isn't going to hurt, so we will take that advice and redo it again in the hope the line is just partially restricted.

other thoughts/ideas:

* Is there any realistic way to replace the line externally on the 216? That was one thought I had. I could drill and mount a fitting into the valve cover and put a flex line on the underside to hook up to the Supply tube on the rocker. Then obviously on the external side it's straightforward, right into the outlet of the Distributor valve. In this method I could monitor PSI to the top end separately also.
*Another idea I had was to run a second electric pump (if the issue ends up being not enough volume from stock pump + some bearing wear). This would require some R&D to ensure a low enough volume pump and restriction as needed so the top end doesn't get too much oil, which would be easy to do!