VCCA Home Forums TECHNICAL - 1945 AND NEWER 1949-1954 216 spun bearing

I recently acquired my granddad's 1953 Chevy 3100. With the engine running, I could hear a clear knock from the 216 inline 6cly.

I dropped the pan and found lots of metal in the oil. I gave each connecting rod a good tug Found one has some play. Actually lots of play. So I opened up the bottom of the connecting rod and found a spun bearing. The crank journal looks and feels smooth.

If you were in my shoes, what's the next move?
1) Do I attempt to get a properly sized bearing, clean everything up, put it together, and give it a try?
2) Or take this thing to a machine/engine shop and let the pros do their thing?

I'd like to try option 1, and am wondering if there may be a couple of easy checks/measurements I can first take to assess this option? And since these don't appear to be original bearings (they look like inserts to me), I'm not sure how to even order replacement bearings (but I presume that will involve measuring the crank).

Thank you in advance for any advice.

Here's a pic of the spun bearing
[img]https://photos.app.goo.gl/RRydCgdQznsz9bTg7[/img]

That bearing looks like tree bark not a bearing! Nasty!
Option one. At least check the surfaces and clearance of the other 5 and maybe get someone to mic the crank to see if it's tapered and size the bearing insert needed. It's not a race engine. Repair the one rod, clean the pan, align the oil troughs and away you go. Just do a couple really short oil changes to get any shavings out.
You could do a compression test on the remaining 5 just for a feeler but it sounds like it was running fine besides the noise...

Hello Aub1953: insert is toast! First, mic the crank for size and or/out of round. You will to need to know that to find out what you need to do before any fix can be done. Good luck david(POPS)

The bearing inserts pictured are not original. A 1953 216 DID NOT have inserts but rather the bearing material (babbitt) was applied directly to the connecting rod. I suspect it is a rebuilt engine that had the rods converted to inserts. When this was done the crank shaft was usually turned down to an under size so the bearing journal will need to be measured for the corect size. If the insert spun in the connecting rod the rod is probably also damaged.
There should be an oil grove going around the center of the bearing. The lack of that grove probable cause the bearing to fail DUE TO GETTING INSUFFICENT OIL.

As Gene said about the oil groove. I would check the other rod bearings also. Did the cap have the scoops for the non pressurized rods?

Thank you all for the very helpful replies.

At a minimum, I'll mic the crankshaft.

Other items to do include check the other bearings for an oil groove, check compression, clean everything up including oil passages.

I'll get a photo of the connecting rod cap in case y'all might advise me on it's suitability for use, or whether it appears damaged. It seems ok, but I have no experience evaluating those.

Thanks again!

Yes, the connecting rod caps all have scoops for non pressurized rods. I assume that's a good thing?

Yes. That's how the rod bearings get oiled at idle, the dippers dipping into the oil troughs and forcing the oil onto the bearing surface. At high speeds the squirters do that. That brings up a point. Why did the bearing spin? Are the nozzles properly aligned to the dippers? If not, the bearing(s) won't be properly oiled and will fail.

Great info. I'll compare alignment of the squirter nozzles across all of the connecting rod bearings, and see if something looks off about the one that should be lubricating the spun bearing.

Is there a recommended approach to verifying that the squirt nozzles are open and delivering oil? I'm wondering about blocked oil passages as another culprit.

On the flip side of blocked oil passages... while under the truck, I noticed a small break in the line that carries oil from the bottom of the oil filter canister. I'll be replacing that line. But I'm also wondering if that could be a culprit here? Any chance that line leads directly to the squirters for the connecting rod bearings? If that line had intermittent partial loss of pressure, then maybe a localized oil starvation occurred?

To check the "squiters" place a garden hohe to the main feed pipe in the center. Keep the pan fairly level and with low water pressure all should deliver oil equally and stream hitting the same location. The oil line leak would not have caused the problem as long as there was enough oil in the pan.

Aub1953

If your crankshaft has been ground there should be a stamp on one of the counterbalances indicating how much. Also you should be able to look at the back of a rod insert and it "should" indicate PN & size i.e. 010, 020 or 030 if under size (not the one that spun). You really need to mic the crankshaft and the connecting rod to make sure that neither one is out of round. Something had to cause the insert to spin. Either lack of oil, material failure or improper installation.

You also need to look at the oil troughs to see if they're aligned and the same height from the top of the pan. There are tools for precise alignment of the dippers, troughs and squirters but they are rare these days and expensive IF you find a set. I had to pay several hundred dollars for my set a few years ago. You can get pretty close by using the eyeball method above but if you want exact you'll need the tools.

Update.

I checked the oil nozzles. They all appear to squirt water about the same rate and arc. I scrutinized cylinder 2, since that's where the bearing spun, and it looks consistent with the other nozzles.

I mic'ed the crank, at the connecting rod journal for cylinder 2. Also did cyl 3 for comparison. Repeated three times for each, and compared. Came up with 2.277 for both cyl 2&3 journals. So this crank was machined down a bit during a previous rebuild.

Visually, cyl 3 journal is shinier than cyl 2 journal. I would describe cyl 2 journal as hazy. Next I plan to lightly buff the surface of cyl 2 journal with long strips of 2000, 2500, 3000grit wet sandpaper. Will wrap strips around and go back and forth. Then will remeasure with the micrometer. If it checks out, then I'll throw a set of bearings in it and give it a go. Will keep an eye on it and change oil frequently at first.

The good bearing from Cyl 3 connecting rod has the following markings:
3-71 G
CB 503 B

Google suggests that's a Clevite Bearing, number 503B.

Any idea what the 3-71 G indicates? Maybe date of manufacture?

I hope everyone is doing well, and again I thank you for the excellent advice. This forum is a great resource.

Lay a straight edge across the pan and measure the depth of the troughs. They should all be the same. If #2 is further down it's possible the bearing was being starved at idle by the dipper not getting enough oil.

In looking at the 503B on Google. If they were oversize. They would be marked 503B-10 for .010 or 503B-20, 503B-30. Indicating the oversize. This indicated your bearing are standard.

Thank you Keith. That makes sense.

I'm just confused about the micrometer measurements I took from the crank journals, because those journals appeared to have been machined down. I had assumed that meant I have an undersized bearing to fill that gap.

But maybe I was thinking wrong? Does it make sense that the crank journals would have been machined down in order to accommodate a standard replacement bearing that is thicker than the original Chevy bearings? I just don't know enough enough about how these types of bearings would be retrofitted intro these engines.

I'm rambling. Thinking out loud.

Let me simplify my question. Are replacement style standard bearings (e.g. Standard Clevite cb503b) thicker than the original?

I guess I'm about to take more measurements on these bearings and do some math.

The STD rod journal diameter of the 1953 216 crankshaft is between 2.311 inches and 2.312 inches. From above you say that you mic-ed the crank and the diameter was 2.277 (2.311-2.277 = -0.041) so it appears your crankshaft has probably been ground -0.040 under-size and the connecting rods were resized to accommodate the inserts. I would look for 0.040 undersize inserts. NAPA used to have them. And, I know Egge has them. I would re-mic the crank to make sure it is not egg shaped as that insert looks awfully beat up to have not done some damage to the crank other than scorch it but hopefully not.

Mike,
Thanks for your reply. I will carefully recheck for any out of round. Just been busy!

My math came out a tad different than yours.
2.311-2.277 = 0.034

Your math is correct. I can't trust my fingers anymore.

For insert bearings the inserts generally came in Standard, ,002" thousand under size, and .010, 020.030 and .040 under sized.
The rebulders would have used .010" and up.
If it is a rebuilt engine the rebuilder would probably have installed aluminum pistons rather than the original cast iron.. A magnet would be the test here.

Just thinking out loud. Any idea how many miles ago the engine was overhauled? And they could have put standard bearings on an undersized crank. Of course the oil pressure would have been very low with that combo.

Thank you very much for the continued feedback, questions, and thoughts. Much appreciated.

Not sure how long ago the engine was rebuilt. My uncle would know, but he passed away.

Crank journals measure round.

Made progress on the truck today. Realized I had not removed the top half of the good connecting rod bearing, so I popped it out. Lo and behold, it seems to have a code that indicates that I have 0.030 undersized bearings!

For others in this situation, I'll provide a link to two photos and a description of what to look for.
The pics...
One end of the bearing has the part number "CB503B" stamped into the metal
https://photos.app.goo.gl/wn25PnYw4RmJJXiG9

The other end of this same bearing is not stamped, but rather has a slightly worn away printed/painted code that reads "30 U.S."
https://photos.app.goo.gl/d4v5dKNRfYq2pQP38

I'm interpreting that as 30 undersized. And now that I know what to look for, I can faintly see this same code on the lower half of this bearing.

I can now order a new set.

Hope this info helps other folks in this situation.

Well, ordering these bearings isn't so simple.

Anyone know of a good source of cb503b-30 ?

Egge has every other common size, from 0000 to 0.05

I found websites that list this bearing, but they are out of stock.

Didn't find these on eBay.

Any leads appreciated.

Glad you found the .030 on the shells. Have you tried The Filling Station, Chev's of the 40's. Jim Carter. NAPA.