The Stovebolt Site Forums The Shop Area Engine Shop 235 Main Bearing Availability

Hey all,

When I got my block back from the machine shop about a year ago now, the machinist said he couldn't get main bearing inserts from any of his suppliers. I ordered some back in October from Rock Auto, and they got put on back order and finally got cancelled in February. I've since been looking online, ordered from a Canadian parts source, and the order subsequently got cancelled again.

Has anyone else had trouble finding main bearings? Rock Auto says the ones I need are in stock now, but won't get here till mid July. Hoping to get some sooner. I still have a couple sites to try, but thought I would see if someone can point me in the right direction to save me some time searching.

Thanks,

Mark

Mark,

Since you didn't let us know what "235" you have it may be kinda hard to correctly answer your question.

I checked back in your previous posts and see you mentioned you were working on rebuilding a '55 - 235, but no confirming info on what the block casting number or serial number stampings are.

We need that info before we send you off on a wild goose chase for main bearings.

Another thing to know is what your crank mains measure. Are they stock, or machined down to correct a defect and require corresponding undersized bearings. Your machine shop should have provided you that info so you could order them in the past.

If you can get us up to speed on your block ID information and what the crankshaft main bearing journal dimensions are, we will be better able to try and help you find a possible source for bearings.

Dan

Mark,

After a little more reading tonight, I see you posted many more details about your "235" in your Project Journal just posted today.

The only detail I think left unanswered is what your crankshaft mains are measuring at???

That's "must have info" if we are to try and help you locate the correct sized bearings.

Can you update your info here?

Dan

Olbetsysdad I finally landed minus .002 mains for my full pressure 235 on E-bay. Lot of bearings on there. 40$ fixed it 12,000 miles since 2018.

The mains that are really scarce are the ones for 54 and early 55 235 engines, the ones with the locating dowel pins in the upper bearing shells. That's particularly true for the .030 undersize bearings. There is a way to make the later type bearings for late 55 through 62 engines fit by doing a little simple surgery on the block with a die grinder or a Dremel tool. Drop me a PM and I can outline the procedure for you or your machinist. The later model bearings with the locator tab for the upper bearing shell at the parting line between the block and cap are much more plentiful and less expensive than the earlier type bearings.
Jerry

Hey Dan,

Guess I didn't post the specifics because I wasn't expecting to get anyone to find an exact purchase link for me. More wanted to know if any suppliers were known to have them and I'd source the specific bearings myself.

That said, always happy for as much help as I can get. Made a mistake on my journal post earlier today on the block casting number. It's a 1955 block, not a '54. So was casted on Dec. 28th, 1955. I need .01 oversize.

Thanks,

Mark

Jerry,

Reconfirmed my block. Hadn't looked or worked on it for a while. It was cast in December of 55, so late 55 235. I was searching the wrong year the past few days. I'll go back and search correctly.

Thanks,

Mark

Fixite 7, ordering from ebay scares the [censored] out of me. Found some '235' main bearings there yesterday, but the box in the picture was labeled for a Ford V6 or something.

Mark,

Another thing to clarify. You mentioned you need ".01 oversize". Is that what your machinist told you, or perhaps was the crankshaft reground .010 undersized???

I know it might seem kinda butt backwards, but an "undersized" bearing is one that fills up the space made by regrinding the crankshaft bearing journals smaller than they were originally. It's my understanding that an "oversize" bearing is meant to be used when the block (not the crankshaft) was machined so the main bearing saddle size is larger than stock (no change to the crankshaft main bearing journal sizes).

Jerry may be able to explain this better than I have and I bow to his better knowledge.

Best Regards,

Dan

PS: Getting on the late side here. Will check back in the AM and depending what you reply, will see what may be found for your need.

The bearings for the late model 235 will be Federal-Mogul part number 960M or an equivalent part from another manufacturer. I believe Sealed Power uses the same numbering system as Federal Mogul. If you happen to have the block with the locating dowels in the upper bearing, the F-M part number will be 853M. Those are the scarce ones. It's possible to modify the early block to use the 960M bearings, however.

There are several sets of 960M-10 bearings on Ebay at the moment. For instance:

www.ebay.com/itm/115369880765?

DO NOT RELY ON THE DATE OF MANUFACTURE TO ORDER THE BEARINGS! Physically confirm that the upper bearing shell locating tabs are at the parting line where the main cap meets the block! BOTH sets of bearings have locator dowels on the lower bearing shells.

Yes, a reground crankshaft needs undersize bearings, since the shaft is ground to a smaller diameter to compensate for wear and make it round again.
Jerry

There's a way to modify stovebolt engines to run main bearings for a big block Chevy V8, but it involves some pretty sophisticated machine work, and welding up the first two main bearing journals of the crankshaft. It's definitely not part of a backyard rebuilding job.
Jerry

Mark,

After Jerry's comments about making sure exactly which engine block you have, I would suggest it may be best to not make an assumption based on the "casting date" info you provided, but we need to know the actual "casting code" from the block to be certain which one you have.

Can you provide a picture of the block casting number (or at least report back with what it is) so we can make sure we aren't giving you inaccurate info please?

Thanks!

Dan

If that block was actually cast in December of 55, likely that is a 56 production year block. The factory shut down for about a month starting September 1,1955 to retool for the 56 model year's offerings. A December casting date would indicate a 56 block cast about 2 plus months or so into the 56 production. So you might want to shoot a photo of what the main bearing saddle of your block looks like just to see if we can sort out and maybe confirm the main bearing issue. The earlier 54-55 bearings might be the wrong bearings. Also, might take a look at the distributor pad and see if anything is stamped on the pad. Lastly, when you took the motor apart, was there a rope rear main seal or an orange neoprene seal? When you pulled the crank, were there any thin brass shims between any of the main bearing caps?

Gdads51 There are no oversize bearings (on the O.D.) out there. They align bore the block back to original bore size,which raises the shaft slightly higher in the block causing the pistons to rise above the gasket decks. That is the limiting factor. An undersize bearing has more "meat" ( thicker) to take up what was ground off of the crankshaft as you said.

Nothing- - - - -repeat, NOTHING beats actually looking at the main bearing bores in the block to see which type of bearings you need. This is not idle chatter- - - -I've "been there- - -done that- - - -got the T shirt!" When we rebuilt John's 261 that the seller had described as a "1954 with a high water pump" I sourced main bearings based on the block casting number- - - -the hard to find ones with the dowels in the upper bearing shells. While doing the block cleanup prior to reassembly, we discovered that the block was a "replacement" item cast in 1959, and it had been machined for the later model bearings. So- - - -since the proper bearings were not available locally, I did the logical thing and drilled the main bearing webs to accept the older style bearings. Now the next guy who gets into the engine can use either style as replacements if it ever becomes necessary. It probably won't be me- - - -unless I set some kind of old age record!
Jerry

Fix,

Thanks for correcting my info on the "oversize bearing" statement! Never too old to learn something, right?

Dan

OlBetsysDad Well I know it's kind of a turkey-shoot trusting some stranger out there. My mains were only 40 bucks and he paid to send em. It showed on the box "old weezer " Written on there. When they arrived I could tell they had been installed but never run and "old weezer " right on there. I rolled them in in the truck perfect fit for my 235 and they shut up a bearing noise like I have heard before,not a knock but a noise that when oil pressure hits it it stops. Have run em about 12,000 miles since 2018 smooth,quiet,30 pound gage pegged full time. Keep trying you'll hit some that look right to you,is OK to mix brands if you have to they don't know any better. LOL find it,fix it, go to truckin !!!!!!!!!

Piston deck height isn't the limiting factor on line boring (I've done dozens). It's the fit of the crankshaft and the cam. Stovebolts have a gear drive, so the teeth can bottom out as the crank is raised in the block. Chain drive engines like a Chevy V8 can get a sloppy chain fit and late cam timing after a line bore. There's actually an "engine rebuilder's" timing chain available for some engines that is a TINY bit shorter to compensate for a line bore. Raising the crank more than .002" during a line bore is considered to be a bad practice- - - -most of the machining is done to the main caps after shortening them about .010" in a milling machine.

Air cooled Volkswagen engines do have oversized OD main bearings available, since the two halves of the crankcase form the main bearing bores. I've installed over/under mains on a VW rebuild- - - -oversized bearing OD in a line bored case, with an undersized crankshaft.
Jerry

Gdads51 I'm glad to help out on all of that,in another life I ran the portable crankshaft grinder on those last babbitt rod chevies. Believe me was I glad to stand up at the floor model big grinder !! That shop was an aircraft shop too where you really learn,happy to say we never lost a crop duster jnto the fence row !! They were cowboys at that too ! Powerful radial equipment !!

This is all very interesting. Glad I posted. Didn't realize my block was walking a line. The casting date stamp is L 285 so December 28, 1955. The stamp next to the distributor isn't really clear in the picture, I'll have a look after work. I've always had trouble matching this stamp to info available online due to being in Canada. I'll also post the casting number after work, as it's hidden in the picture, but that's more for interests sake. Pretty sure I've looked up the casting number in the past, and don't remember it pointing to a '56, but that was a while ago. . .

Jerry and others, thanks for the tip on physically checking the bearing. I'll pop a bearing cap off after work. Just for clarity, I assume the positioning tab I'm looking for is the one I've circled in the attached picture?

After reading the info presented in this thread, I'm finding searching for bearings quite frustrating. When I mistakenly searched for bearings for a '54, the 460M part number repeatedly came up. I was under the impression that the difference between the 460M and the 853M was that the 960M was grooved for half the bearing and the 853M was grooved for the full bearing. One website seemed gave a choice between a 960M and an 853M for the '54. At the same time, this is immensely entertaining. Putting problems/puzzles to bed is fun.

As for the bearings being under/oversized, guess that's just a vernacular issue on my part. .01 was taken off my crank. I assumed the extra material on the bearing would result in calling it oversized. I'll adjust to the vocabulary of the pros.

Last thing, bearing cap shims. I honestly don't remember if the shims were there. I am aware of them as the original engine for my truck was a 216 that I stripped a couple times. However, when I mocked the engine up to measure for valve to piston contact and I snugged the main bearing caps, with the original non-undersized bearings, I couldn't turn the crank with the bearing caps not even fully torqued yet and had to back off the bearing bolts. From that, I'm assuming I'll need the shims, and thinking they were there and I tossed them anticipating buying new ones.

On a side note, my machinist told me I could get away with using the original non-undersized bearings if I needed too. I'd rather get the proper sized bearings though.

Thanks,

Mark

One bit of advice concerning machinists. If your guy says you can run standard bearings on a reground crank, you need to RUN- - - - - do not walk- - - - - away from him, and take your engine with you! He's going to cause you untold expense and grief before the job is finished. I was GIVEN a 261 engine that was assembled with standard bearings on a .010" undersized crankshaft. It ran less than 20 minutes after a complete rebuild and ruined the crankshaft.

The tab you highlighted is the one to look for. The design was changed in the mid-1950's to make it easier to change main bearings with the engine in the vehicle. The ones with the big dowel pin in the upper bearing requires the crankshaft to be lowered nearly an inch before the upper shell can be replaced. The one with the tab at the parting line can be rolled out by lowering the crankshaft just a few thousandths. Shims between the block and the cap supposedly were eliminated when the design changed to use the tabbed bearing, but I've seen them used on the later model bearing on rare occasions. If the crank locks up or gets very difficult to turn when the caps are tightened, I suppose using shims will be OK- - - -the idea is to get as close to .0015" oil clearance as possible, either by grinding the crank to fit the bearings, or shimming. Good luck!
Jerry

Jerry,

I'm curious about the engine failure you're talking about. As a hypothetical, let's take my engine. If I torque the bearing caps down, my crank locks, which suggests I'm well under .0015 spec clearance, with the original non-undersized bearings. If I shim the bearing caps, I have control over the bearing to crank clearance, at least up and down. So if I get the clearance to spec (.0015) what's the failure mechanism? Is there a risk that the side to side clearance is so out of whack that oil loss though the horizontal sides of the bearing starves the bearing? But anytime you shim, you're affecting the up and down clearance, so I would think this could always be a problem? Does the torqueing down of the bearing caps snug the bearing all the way around the crank so clearance is uniform?

I do deal with some high HP high speed rotating equipment in my work life. So now curious if idle speed is enough to initiate hydrodynamic lubrication, or whether the bearing is operating in a mixed or boundary condition at idle? And to take this further, how does the reciprocating motion on the rod bearings affect the hydrodynamic condition when it forms?

Looks like I turned up some research to do. I'll still purchase the correctly sized bearings in the end, but looking to understand how these bearings operate better. The constant load/constant rpm stuff I work on is a little bit of a different animal.

Thanks,

Mark

Usually, the crankshaft is ground perfectly round, so is the main bearing bore, and there's a slight egg shape built into the bearings. That can be measured by torquing up the bearings with the crankshaft removed and using a dial bore gauge to check the diameter at various positions around the circumference of the inside of the bearings. They're SLIGHTLY larger diameter at the parting line where the halves meet and there's a tolerance specified for oil clearance- - - -usually something like ".001-.003". In practice, .0015" is the target to shoot for, particularly on the rear main bearing where clearance approaching the maximum tends to cause the rope rear bearing seal to leak from the crankshaft bouncing up and down. We are quite literally "splitting hairs" here, as an average strand of hair is less than .002" thick.

Back in the dark ages of poured Babbit bearings, a new bearing was coated with Prussian Blue, and the bearing material was scraped until there was a smooth blue smear as the shaft was turned, indicating "no high spots"- - - -then shims were added to establish the right oil clearance. The accepted procedure before the invention of Plastigauge was to sandwich a thin slice of shim stock between the bearing cap and the shaft, and add thin layers of shim stock between the cap and the block until the shaft could be turned with a firm tug on the flywheel. That method still works- - - -Plastigauge is for rookies! Shimming stovebolt rod and main bearings is a holdover from the days of poured babbit- - - -as production techniques and tolerances improved (mid-1950's) quality control and machining accuracy eliminated the need for shimming. In certain situations where incompetent machinists get into the mix, a little tweaking with shims might be necessary.

Yes, there's enough hydrodynamic lift on a crankshaft at idle speed to center the shaft in the bearings, as long as sufficient oil volume is supplied. As volume and pressure increases with speed, theoretically there should be no metal to metal contact at all in an engine, even at the camshaft.

The engine failure I referenced was caused by the crankshaft bouncing up and down on bearings with a diameter .010" bigger than the crankshaft- - - -on both rod and main bearings. That's over 3 times the maximum oil clearance. I'm amazed it didn't spin a bearing somewhere, instead of just beating up the crankshaft!
Jerry

Thanks Jerry,

Really appreciate this type of discussion. Also appreciate the insight into how manufacturing techniques/quality control has played a role in design features over the years.

My take away from this, is that if I could fit the original non-undersized bearings to .0015 clearance, I won't have the same failure you experienced. Correct?

Thanks,

Mark

Don't try to reinvent the wheel- - - - -Measure the crankshaft diameter and buy the appropriate size bearings. Use an accurate micrometer- - -not a caliper, even a digital one. A .010" undersize shaft will have the following diameters- - - -four different sizes, getting bigger from front to back:


#1 (front) 2.6735-2.6745"
#2 2.7045-2.7055"
#3 2.7355-2.7365" (Thrust bearing)
#4 2.7665-2.7675"

"Standard" shaft diameters are .010" larger than the above dimensions. If your crankshaft does not measure within the above tolerances. you need to find a machinist who knows what he's doing and get the other guy's mess corrected, even if it means going to the next undersize. NO EXCEPTIONS!
Jerry

Somebody else screwed up the 261- - - -I just inherited the other guy's mess and benefited from his stupidity by getting a free, very scarce "big bore" engine block. It's going to be the base for a 300+ cubic inch stovebolt engine with a stroker crankshaft, H-beam connecting rods, and forged pistons from a turbocharged Buick V6.
Jerry

Jerry,

I've already measured, and all journals are within spec for .01 under. I will be buying new bearings. My 'take away' was a hypothetical, but an important one.

The machinist I used has one of the best reputations in Alberta for building race engines. And this is far from the first 235 he's done. In fact he had one in the shop the same time he did mine. I have every confidence in him, so I'd appreciate it if you'd stop implying that he made a mess of my engine.

As always, I appreciate your knowledge, but please continue to go in depth as you did a few posts ago. That allows me to learn.

Thanks,

Mark

Had a chance to pull a bearing cap off and check other info. The bearing does have a positioning tab, so I'm good with the 460M bearings. Block casting number is 3835911 and the identification number next to the distributor is 1744C. Pics attached.

Thanks,

Mark

If you can roll one of the bearing shells out of either the block or the cap, the undersize should be stamped on the back of the bearing. That's almost as good as measuring the diameter of the shaft. You definitely need to determine what size shaft you're dealing with before buying replacement bearings. If you're doing a full overhaul, the crank has to come out for cleaning and polishing anyway.

If you have confidence in your guy's ability, that's good, but I simply cannot imagine anyone telling a customer that he can use different size bearings than the crankshaft diameter. Maybe I misunderstood that part of your description of the situation.
Jerry

Mark,

Just a follow-up after seeing your info on the block "casting number" and stamped "serial Number".

The casting number "3835911" decodes in my resource book as a '53-'55 235 block car engine backed by a Powerglide transmission. However, that info is based on US made 235 engine resource data. I did come across a comment in a link from an earlier Stovebolt conversation on Canadian 235 identification that listed that casting number as one used for Canadian '53-'55 Chevrolet 235's. It didn't indicate car or truck specifically, nor what transmission may have mated up to it.

As your truck is Canadian made, I can only guestimate that your block is still a '53-'55 configuration which uses the "853M" style main bearing set with the upper half locator pin. Your picture of the upper shell half exposed also helps confirm that. Also, since your truck/engine is Canadian built, the stamped serial number doesn't conform to the US made coding. Perhaps a fellow Canadian Bolter can add some info on the serial number???

Back to the main bearings. I think you meant to say "960M" and not "460M" to mean which bearing set you're "good with", but in this case I think you actually need the "853M" set.

With that in mind, I did some web searching this morning (using the "853M" set and known cross-referenced part numbers for the various manufacturers that made these) and may have found something of interest for you.

Sending that in a PM for further discussion/consideration.

Have a great day!

Dan

PS - Going to be away from my computer for most of the day as I'm heading to a local car/truck show with a nearby Stovebolter. Will check back in later.

Hotrod Lincoln Any blueprint engine builder knows you can buy timing sets to overcome tight timing fit up. Just not stovebolt,have you align bored a lot of stovebolts blocks ??

Dan,

I had thought with the locator tab visible in the picture it was the 960M bearing (yes typed 460 in error). I'll see about popping a bearing out to confirm 100%. And thanks for the PM, much appreciated if it is a 853M bearing.

Thanks,

Mark

Well, rotating a bearing out is easy! No pin, so I'll need a 960M bearing. This can be put to bed, except for having a set show up at my house.

Looking closely at the stamp on the bearing in the picture, it looks like the original bearings were .01 undersized. I had assumed they were not undersized at all. Solves the mystery of why my machinist told me I could use them if I needed to. He must have just polished the crank, which I find surprising. That engine did some hard work in a 1 1/2 ton grain truck, however, it was only for a month out of the year.

I had measured the journals previously and all were .01 under original spec.

Thanks,

Mark

Mark,

Big Congrats on getting it figured out for sure and you didn't need to try and chase those 853M style bearings anymore!

I will blame my "old and unreliable eyes" for missing that little tang in your earlier picture. Also may have had something to do with the fact I was so busy trying to follow the thought trail of the casting number, that I overlooked the obvious.

Best of luck on the hunt for the 960M bearings. Would be glad to offer help if you have trouble trying to locate those.

Dan

www.ebay.com/itm/253418416030

Jerry

Thanks Jerry,

Already ordered them from your previous ebay link.