The Stovebolt Site Forums The Shop Area Engine Shop 1955 Bearings, WTH : )

So yesterday I pulled the rear main cap to do a "sneaky pete" rear seal install. When I pulled the cap and looked at the crank journal I was just not happy. See pics. I decided to pull all of the caps. Only the rear main bearing was like this. The rest were shiny and smooth. I measured the rear bearing surface on the crank in the block (Used a decent vernier caliper, not ideal. I get it) and it measured very close to spec. Not sure if I was in a high spot or in a groove. Don't remember the numbers but I'm not sure what I had for breakfast. Seems the crank needs a grind. Didn't pull the rod caps yet so nothing there. While I know this is a problem, what would cause just the rear bearing to wear like this? So exciting, can't wait until tomorrow... Thanks!

Oh, and note that the bearing material squeezed (?) out in one of the pics.

Yeah, with the insert down to the copper, you're going to need to renew the inset at least. I'll bet a shop will say your crank needs to be ground.

Is this an engine with babbit rods or inserts?

If you fill out a signature with your truck and engine info, it would show up on all your posts and be helpful to those who are trying to help you.

Are you able to roll the upper bearing shell out of the block? There are two designs of upper main bearing shells- - - -one has an anti-rotate tab at the parting line where the cap meets the block, (1955-62) and the other (1954-early 55) has a locating dowel similar to the lower bearing in your first picture. The later model upper bearing with the parting line tab can be rolled out and replaced by loosening the other main cap bolts a couple of turns and tapping the bearing shell out. The doweled upper bearing requires the crank to be lowered almost an inch before it can be removed.

If the upper bearings can be removed, you might be able to replace all the main bearings without a full teardown, after doing a "shoeshine" polish on the crankshaft with a strip of emery cloth. Just be sure to do a thorough cleanup of the sanding grit. The doweled upper main bearing sets are almost impossible to find these days, particularly in certain undersizes.
Jerry

Look closely at the rear main cap to make sure it matches the others in grain texture and color. Could be some one change the cap due to damage or being misplaced, and found one that fit, but not quite right. A line bore may be in your future.

Well the whole truth is that I did change the seal. Also thought I'd just let the bearing ride since it was a running engine before I took it apart. After a bit of clarity I decided that leaving it as is would be a bad idea. When I installed the upper part of the seal I did drop the crank about 3/8", maybe more, to get the new seal in. While doing that the upper bearing did move and I had to slide it back into place.

I'm GUESSING it's not the doweled variety. Block is dated H55 (August '55?), So I'm GUESSING again that between the movement of the upper bearing and the date it's not a doweled bearing. Thoughts?

The casting number confirms it's a later 1955.2 low water pump position block, so the upper bearing shell should easily rotate out as Jerry said. Your stamped serial number (presuming one is present) will confirm what the engine was originally installed in. Check out the screenshots below for decoding info on the serial number. The first pic is for "truck" engine codes. The second is "passenger car" engine codes, as both engines used the same block casting number.

I agree with your assessment that leaving it as-is is probably a bad idea. A visit to a machine shop I think is in order.

OK, here's an update. I pulled the upper bearing no big deal to get out but there is a protrusion like the lower bearing, see pics of the bottom and top. Non-Dowel or Dowel bearings?

Measured the rear crank journal, was not correct in my earlier post. Going from memory is always a bad idea : ) Measured it in 3 places and was 2.765". Chevy spec for an out of the factory crank is 2.7765-2.7775". So it seems the crank has been cut .010", right?

Also did my best to take the info from the stamp on the back of each bearing. Numbers are:

6954 CAP U 6954 CAP L
D.A.B. 8(3?)-17 and D.A.B. 8(3?)-17
86 86

That's definitely a doweled bearing. The other type would have a notch and tab setup like the attached. (This is a rod cap, but the mains are set up the same way.)

If everything else is the same dimensions, a notch could be cut in the block and caps and the tab type bearings used. Might take some head-scratching to figure out.

Yes, that's the doweled upper bearing. Finding a replacement for that one is going to be difficult, if not impossible. My Federal Mogul shop specifications manual confirms that you've got an .010" undersize crankshaft. That bearing is in terrible shape- - - - -definitely Do NOT try to reuse it.

The Federal Mogul part number for the bearings with the upper dowel is 853M-10. If the engine is completely disassembled to a bare block, the later style bearing set, 960M-10 can be substituted by filing grooves at the parting line for the locator tabs for the later model bearing set. Those bearings are expensive, but at least they're still available from most sources.

www.ebay.com/itm/203613474956?

Sealed Power uses the same numbering sequence as F-M
Jerry

As Jerry says not cheep https://www.ebay.com/itm/1983690593...meta=01KXKH8429QXNHF7WAF1GTZ8HZ&hash

Aye Carumba!

Well, buy once, cry once. When working on a 70 year old vehicle, I'm generally thankful to find parts available at any price.

I agree, they exist so I'll be pulling out some old fillings to get them : )

On another note, When I looked at the ebay link that Jay posted (thanks for that) I decided to see if their "Does it fit your vehicle" function matched my late '55 block. It says "This parts does not fit your vehicle". So, I scrolled down to the part number that the ebay seller had listed for this bearing set. It is MBS1175-010. I just put that number into a google search and came up with this on the Summit racing site https://www.summitracing.com/parts/kaa-mbs1175-010#overview

Same info, same part number, same pics, same "it does not fit your vehicle". They look correct, any confirmation votes on these before I pull the teeeth?

Thanks so much for all the help, priceless!

Oswald - Just out of curiosity, when you checked the other main bearings, did you happen to look at the upper half bearing shells to see if they had the notch and tab design suggested by Kevin above?

Just grasping at straws here to see if maybe in the engines past someone used the mix and match parts method to replace an original bad bearing, or maybe as Joe H suggested, the rear main cap got swapped with something that wasn't checked for proper fit???

Jerry (HRL) can probably answer better on what may have caused the odd wear on the rear main lower shell, but if it was just me noodling the situation, I'd wonder if the rear main cap maybe wasn't properly shimmed for the crank/bearing/cap clearance as one possibility. The concentrated wear towards the rear of the bearing to me seems to indicate the rear main bearing surface either wasn't the same front to back, or the rear main cap wasn't checked/matched to the crank or maybe was improperly shimmed for proper bearing clearance.

Just trying toss ideas out in case it may be of some help.

Oswald - On another little back track question, what's the stamped serial number on the pad directly behind the distributor hole? The stamped serial number should confirm if the engine is a '55.1 or '55.2 series design

Since 1955 was a transition year with both First and Second series, It could be that your engine casting still used the earlier 1954-55.1 Series main bearing retention design that seems to be in play here.

No, there are none of the notches in the block, caps or bearings. See the pics. Also see the pics of the stamp pad. As noted in a earlier post the casting is H55 which I believe is August of 55. Quite late for a '55 block. The serial number is quite high as well indicating late. I'm guess ing this is a block caught up in the transition from one bearing design to another.

Oswald - The "F55Y" indicate the engine is a Flint built 1955 Model year 235, but originally in a Powerglide automatic transmission in a passenger car. It would originally have had a hydraulic cam and lifters. I haven't found anything yet to confirm when the passenger car engines transitioned to the newer style upper half tang retained pieces.

If you are going to have to have the cranked turned again, you'll need to source .020 under bearings for the mains, which appear to be "In-Stock" at Summit.

If you can get the tab style bearings for cheaper, It's really pretty easy to notch the block and caps for them to fit. I did that on my 235 crank conversion on my 216.

Bearings ordered. Will update when I get moving forward. Shim thread coming soon... Stay tuned

BTW, that's not my computer. It's my head...

Just to add a bit of uncertainty to the mix, some of the high water pump 235 and 261 blocks were machined for the locator tabs at the parting line. John's 261 that we built for "Charlie" was that way, and I had ordered the early style main bearings, believing it was a 1954 production block. The casting date indicated 1959, which would have made it a replacement block- - - -early water pump position, and late style main bearings! I ended up drilling divots in the block webs to accept the bearings we had on hand!
Jerry

Yes .... Watching Jerry take a drill to free hand those divots was somewhat ... nerve wracking ...

So then was the dowel not in the hole and caused the issue?

There was no hole for the dowel to fit- - - - -we had to make our own. The block was machined for the later type bearings, without dowels on the top. There was a mismatch between the bearings we had, and the ones we needed, with about a week ordering time for the correct bearings. Easier to make the block fit the bearings we had ordered!
Jerry

HRL, quick question. What grit emry cloth do you recommend to "shoeshine" polish the crank? I have 120 but I suspect that would be too coarse.

I start with 220 and finish up with 320 or 400.
Jerry

OK, seems I have hit a wall. As HRL noted the doweled bearings are impossible to find. No hits on the 853M-10 bearings with the dowels so I orderered the set that jay d posted, the MBS1175-010. They promptly arrived but were incorrect. The thrust bearing was way too wide. I didn't take them out of the packaging so they could be returned but measuring them wrapped up they were about .200" too wide. They're being returned so no problem there.

The MBS1175-010 were from Kanter Auto. I called them and they confirmed that these were incorrect and gave me the correct number, MBS1690.010. Searched that and found a set in St. Louis but they won't ship, in person meet up only. Since I'm in NY that's not practical. No other hits on that number

Anyone here in St' Louis?

Also called Egge, they have them in STD and .002" only and basically told me they were unlikely to be reproduced in the future. Their number was MS1690. no hits on that either.

So as far as original doweled bearings I'm apparently out of luck. HRL and klhansen mentioned modifying the block to accept the bearings with the tangs, going to put up a seperate post on that. This horse has been beaten down. Thanks to all!

The bearings with the wide thrust flanges are for a 216, not a 235. The correct 235 bearings only had about a 3 year production run, some 53's with Powerglide transmissions, 54s and early 55s. The late 55 through 62 235s have the tangs on the upper bearing shells, not the dowels.

It's possible to machine 216 and 235 blocks and crankshafts to use small block Chevy 400 V8 main bearings, but it takes some pretty sophisticated machine work, including line boring, to do it.
Jerry

Odwald - I sent you a PM. May be able to help with St. Louis acquisition.

Get back via PM please.