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this is one of the things I found when we opened up my motor to change the rear main Seal .These are federal mogul .010 Under bearings With about 1000 miles on the motor.The crank surface is smooth and Undamaged and all the rest of the main bearings are in good shape.Anyone care to read these bearings and give options on what went wrong and how to remedy it ? This is/was a completely rebuilt motor .030 over bore.factory reconditioned rods and supposedly align honed. No need to bash my engine builder I’ve moved on from that . Thank you
As Mark said measure the crank journal for taper. If the crank is ok, put the cap on and measure the bore for taper. Put a used good bearing in the main and measure it for taper.
How does the pictured bearing insert measure for thickness comparing worn side to good side? To the eye it would be expected the worn appearing side to be thinner, is it? The chances of one defective insert is slim to none but...
Examine the cap, bearing saddle and the backside of the bearing for a miniscule piece of debris causing an improper seating.
Are the caps numbered? Wondering if by chance main caps were installed in the wrong position.
Examine the main cap bolts to see if any are damaged or bent.
Probably going to find a crank taper issue though.
I numbered the caps when I first opened the motor up from its original state and they are all in their proper places . I don’t have any high end measuring devices but my buddy does who will be coming on Wednesday to have a look and I’ll talk to him about the above mentioned stuff . The right thing to do would be to send it off to a olds specialist but I’m strapped right now . That line in the bearing surface indicates to me there was at least at some point a piece of grit or something that caused that gouge. Thanks for help I’ll post what we find.
On reassembly plastigage all the way across that main looking for an even "squish". I'd also plastigage it in at least two positions. Do it once, clean it up, do it again after a 1/4 turn of the crank.
Please keep us posted...fwiw, I had something like this on a non-Olds motor, got lucky it was the bearing insert. My money is still on Mark's guess of a tapered journal.
#4 Bearing I guess . The next to last at the back on the engine .we will plasti guage it as well ( can you believe I have to order plastigage? They don’t carry it anywhere near me in parts stores )
#4 Bearing I guess . The next to last at the back on the engine .we will plasti guage it as well ( can you believe I have to order plastigage? They don’t carry it anywhere near me in parts stores )
Being number 4 it could also be a balance issue. I’ve seen that before. But question, you're showing what should be two upper halves, where’s the lower for number 4?
The one on the left was on the top and the one on the right was on the bottom
I was under the impression those were FM 108 mains? If so then the full groove goes on the top with the partial grooved half going in the cap.
Or are they Clevites?
Notice the clarity/precision difference in the markings on the bearing backs, by itself that's nothing but it makes we wonder about other standards followed in the manufacturing process/quality control.
Notice the clarity/precision difference in the markings on the bearing backs, by itself that's nothing but it makes we wonder about other standards followed in the manufacturing process/quality control.
Those are the cheap FM’s. They’re full groove just like Clevites. 108M is the race bearing that’s 5/8-3/4 groove.
Nonetheless you have issues.
Yeah I always seem to get the junk because I can’t afford the top of the line stuff so I’ll have to deal with it one way or another. Have a good mind to just replace the bad bearing and beat the hell out it and have some fun while it last . Thanks for the responses I’ll let you all know how it turns out .
Have a good mind to just replace the bad bearing and beat the hell out it and have some fun while it last ..
Jeff,
That is not going to solve a thing and if you keep driving it you take the chance of doing plenty of damage. It looks to me like there was not enough clearance. The wear on the bearing goes almost all the way around. It should only be about 3/4 of the way on each half. Have you pulled another cap to take a look ??
I would pull the engine and take it apart and find out what is wrong. There is no way to properly measure the main journals with the crankshaft still in the engine, period.
By the way there is nothing wrong with the Federal Mogul bearings. They are as good as any of the other major manufacturers.
Bill , the engine is out of the car and and all other bearings are in great shape . The bad bearing only has the damage on the One side . I agree its probably a clearance issue . My theory is whatever made that deeper scratch in the bearing was either the cause of clearance issue or was caught in there long enough to cause the wear . I have a new bearing coming today and we will plastiguage it and see what that tells us . We will also measure the journal to see if there is any variance from one side to the other . If all checks out it will be put back together . the crankshaft was Sent out and turned .010 under and my machinist said he double checked it and it was perfect .we will see . Thanks for the response
My theory is whatever made that deeper scratch in the bearing was either the cause of clearance issue or was caught in there long enough to cause the wear .
Jeff,
That one deep groove was caused by a piece of dirt left in the engine during assembly. It had nothing to do with the wear on the rest of the bearing. It will be interesting to see how the crank measures.
Jeff,
That one deep groove was caused by a piece of dirt left in the engine during assembly. It had nothing to do with the wear on the rest of the bearing. It will be interesting to see how the crank measures.
I disagree. Once you start losing bearing material anything can happen, ie it can roll up and get caught just about anywhere.
However I agree that just replacing this one bearing is a gamble at best. I believe the problem will continue unless diagnosed and fixed properly.
Thanks.
I disagree. Once you start losing bearing material anything can happen, ie it can roll up and get caught just about anywhere.
However I agree that just replacing this one bearing is a gamble at best. I believe the problem will continue unless diagnosed and fixed properly.
Thanks.
If the crank measures properly and the clearance is good on the bearing what else would I do to diagnose and fix properly ?
If the #5 bearing is set up with more clearance than the other four (which is highly likely), then any imbalance at the rear of the crank will manifest itself in the #4 bearing. Imbalance could definitely come from improper rotating assembly balance (as cutlassefi said); in the engine I saw, it came from a torque converter that was out of balance. This caused minor wear on the #5 bearing, but it completely obliterated #4. It also caused it to pump oil out of the rear main seal (rope seal). It also had caused the front pump seal in the trans to leak, as well as wiping the bushing in the pump.
After waiting since last Saturday for my 2 day shipped bearing to arrive it finally came in today . I’m the proud owner of a Clevite rod bearing $&@“@&$(!Napa auto parts finest !
Finally got the bearings i needed ,so decided to play with the plastiguage til my help comes with his measuring equipment.The plastiguage shows just a tiny bit more than .001 clearance on the newly installed bearing which seemed to be a bit tight so i checked #1 and #2 mains and get nearly the same clearance.I went through some of the notes jotted down by the machine shop and it shows .002 on the rear main and .0015 clearance on the rest.He listed side clearance as well 1/2=.014 3/4=.011 5/6=.010 and 7/8=.016 (no idea what these numbers mean but thought i would throw them out there.
Side clearance is the space between the sides of the big ends/crank of the connecting rods. 1/2=.014 means between the #1 and #2 rods there is .014" clearance. This is measured with both rods installed and a feeler gauge between the two rods. That clearance is where the old oil exits as the new enters under pressure through the crank.
About crank bearing clearance at .001 plus to .002 it sounds ok, maybe slightly snug on the .001 plus though. Let's see what some of members say that build many engines
I’ll say it one last time, that engine needs to come apart and be machined properly. Or you can keep throwing band-aids at it like you’re doing. Your call.
I’ll say it one last time, that engine needs to come apart and be machined properly. Or you can keep throwing band-aids at it like you’re doing. Your call.
ill assume this means you dont like the clearances?I would sure as hell like to ship this motor off and have it completely checked ,but as stated above i dont have the funds for that.If i have even a small chance i can repair it with a new bearing and get some use from it ill roll the dice.Otherwise, it will sit in the garage torn apart and rusted till i get back to it ,like the 1000"s of motors are doing right now.I do appreciate everyones advice.
I’ll say it one last time, that engine needs to come apart and be machined properly. Or you can keep throwing band-aids at it like you’re doing. Your call.
Pay attention to what he is saying!!! If it’s not fixed correctly it will cost you more time and money. This is a perfect example of the old saying “if you don’t have the money to do it right, where will you find the money to do it over??”
You will probably get the same amount of use from it as you got this time . . . . 1000 miles. Did you figure out why the rear main was leaking ??
The only thing i saw with the seal was it had excessive permatex right stuff all over the seal surface that makes contact with the crankshaft .That may or may not have had anything to do with it .It did not leak a drop for the first 500 miles.Another 1000 miles might buy me enough time to do it right if things improve financially.
May 31st, 2020, 08:29 PM
!Napa auto parts finest !
