The Stovebolt Site Forums The Shop Area Engine Shop "Low Pressure Oil System 101"

Awhile back someone posted the the basics of how a low pressure oil system works.(216's/early 235's) I was going to print it out because it was very informative and to the point. But like everything else, it slipped my mind, and now I find myself looking at the copper rocker shaft oil line that I broke off at the block wondering "does that go all the way through the block to the driver's side?" And "what is this little doo-dad under the cover on the driver's side of the block?"

Can someone give a really basic explanation of the low pres. oiling system, and the components invoved? Thank you in advance!

I second this request, and I've always wanted to know what a "babbit" is and why it's so bad

Keith, I'm no expert here, I'm just getting started with my 216 myself. But I do know that when I dismantled my engine I had to cut the copper oil line to remove it from passing thru the water jacket.
I figured I would make up a new one later when I reassemble.
I don't know what the little coverd thing is either. Maybe we can get some help on that.
When it come to babbits. My machinist is just getting into pouring babbits since retro engines are making a rebound. He could have done it for me but I decided to go ahead and bore them out and put in inserts.
Just my 2 cents.

Here is part of a previous discussion:
http://www.stovebolt.com/bboard/cgi-bin//ultimatebb.cgi?ubb=get_topic;f=2;t=008745#00 0010

The oil system in the old 216s is known as a low pressure system because the main pressure when warm and at medium RPMs is around 15 lbs. At idle it is 7 lbs or less.

Babbitt: The rod bearing surfaces are made of babbitt which is formed directly on the iron of the rod bore. These rods are shimmed for clearance adjustment. The more modern rods have insert bearings and they usually have several different layer of different metals, the mating surface being babbitt. Babbitt is a soft material with a high lead content. It has the ability to conform to the crankshaft surface.

The rods in the 216 are not fed with pressure from the crankshaft/main bearings. The early 216s had only dippers on the rods, like most early motors. As everyone else moved to pressure oiling of the rods, Chevy beefed up the old design by providing "rod sprayers" that spray directly into the dippers as the RPM builds past idle.

The 216 main oil system branches out from the pump, to the main bearings and camshaft, and to the "oil distributor valve". This little valve, located under a cover on the driver's side of the block, opens up after the RPM and pressure builds up, to supply oil to the rod sprayers and also the rocker arm. To supply the rocker arm assembly, there is a line that emerges from the block, just back of the oil distributor valve. This line loops back into the block, passes through the water jacket and goes up to the rocker arm , passing through the area of the lifters, under the side cover. Chevy claimed that this was to heat that oil to the right temperature. I think that it was just their way of routing the line.

I sent a PDF file to some of our members here detailing the oil line. Also there is an installation instruction in the Chevy truck manual.

Pakrat,

I was one of the participants in the earlier thread you described. Rather than trying to locate all of the fittings and tubing etc. to replace that line, I just ordered the kit from Jim Carter's. It was a little bit more, but all there, and I didn't have to search all over town to find the parts.

The change is very easy. It took all of about 15 minutes to complete, and yes, it does go all the way through the block. I'm using a 39 block, which is a little bit different than the 46 block I replaced. On the 39, the line comes out under the side cover directly behind the distributor, while on the 46, it comes out further back towards the firewall. None-the-less, I took off the covers, removed the dist. cap. and had the whole thing plumbed in a few minutes. Good luck.

Truckernix and Jed, thank you! Oil distributor valve. That would explain the spring loaded disk. I'm assuming it keeps oil down in the bottom end where it is needed until the rpm's go up, and then opens with the added pressure. If oil was distributed throughout the motor at 7psi, there wouldn't be enough for the rods? Is that the thinking behind this?

As long as all of your fittings are good (with the exception of comp. ferruls) you should be able to replace the line with flexible copper tubing right?

Thanks alot guys, I'm glad you remembered the disscusion I was talking about!

Pakrat,
I haven't worked with this because the 1951 Canadian truck 216 doesn't have that line arrangement. However, that line must be sealed on the outside where it enters and exits the block.

I don't know the exact design reasons for the oil distributor but I think that they worried about the mains first. It was a good rugged motor and performed for many duies. It must however have cost Chevy a fortune to continue making those rods. They have a very thin Babbitt, much thinner than the older Ford motors. They said that the thinner babbitt stood up better.

Yeah, the line runs through a pipe/compression fitting on either side of the block. So the water jacket is sealed. I would think if a fella was in a pinch, he could put a pipe plug in both sides of the block, and run that line any route you wanted to. I'm going to replace as stock.

I didn't realize the Canadian motors were different.

Keith, If you're using a 48 block, you can probably get away with getting some new ferrules and using your current fittings.

In any case, you can use flexible copper tubing, and that's what you'll get if you order the kit. Only difference on the kit, it comes with the sweat fitting already in place.

In the case of my 39 block, I about had to use the "sweat" fitting because I didn't have clearance to make the bend up the side cover and clear the cover itself if I used a comp. fitting and ferrule.

My previous motor (a 46) was a different story. It had regular fittings and comp. ferrules. On the 46 side cover, there was also an outward indention in the side cover that allowed more room for the tubing coming out of the block and bend upwards. It wasn't there on the side cover on the 39 motor.

Unfortunately, as I stated earlier... The lines don't come out in the same place on the different blocks, so I wasn't able to use the 46 side cover.

If you're going to buy tubing, I would suggest that you get between 2.5 - 3 feet of it. You should have plenty extra, but it will give you alot more to play with, and what the heck, it's cheap.

This helped in my case, as on the bend to the oil distributor, I had to bend it differently than the stock bend, as it wouldn't clear my exhaust. I guess that's what happens when you start mixing parts. Good Luck.

Hey Jed, looking back at the previous disscusion on this topic, it seems as though you happened to be in the "right place at the right time"! If not you proably would've pumped all your oil right out, or into the water jacket.

Keith, You're right. That posting came at just the right moment. However, it didn't turn out as bleak as what I thought it was going to be.

I originally thought that the worst would be what would happen. However, the way the fittings seal around the tubing and close off the water jacket, I think would prohibit that from happening. As long as the motor was running, it was oiling everything it should have, and nothing it shouldn't have.

However, when you stopped the motor, it would leak oil out from around the tubing like crazy.

What surprised me the most, was when I drained the block to pull the old tubing out of the water jacket. The antifreeze was green and good as new.

Now if I could just get everything to clear my exhaust manifold and find the time to put it all back together, I could be driving my truck. Oh well, I guess this is my life's lesson in patience.