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Old 12-16-2013, 07:35 AM
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eating up main bearings

i got my old engine torn down and was quite surprised at what i found , engine only has about 3k miles on it , everything looked good except for the main bearings

center 3 lower halves




center 3 top halves



bottom half front and rear main ( flash washed out the copper showing threw but it was dead center on both)


im curious as to what u guys think is the cause
#1 to much power and its trying to run over the crankshaft
#2 not enough clearance
#3 oil starvation
#4 other ?

the rod bearings were pefect , no other signs of distress in the engine except for those 3 lower mains ( even the crank doesnt have a mark on it )

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Old 12-16-2013, 08:20 AM
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My vote is #3
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Old 12-16-2013, 08:22 AM
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Originally Posted by MouseFink View Post
My vote is #3
i had some ppl suggest that as well but wouldnt most all of the bearings show signs ?
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Old 12-16-2013, 08:52 AM
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I'd lean more towards an alignment issue,or,a warped crank.If it were oiling,it would be showing up elsewhere as well.
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Old 12-16-2013, 08:58 AM
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I'd lean more towards an alignment issue,or,a warped crank.If it were oiling,it would be showing up elsewhere as well.
we put the crank in a lathe , and it spun true on the mains, ill have to get a machined piece of roundstock and run it threw the main bores and see if any are out of line

this engine is getting freshened and then put in my truck so i wanna see if i can find the source of the issue
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Old 12-16-2013, 09:13 AM
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To me it looks like a block alignment issue,not the crank (not concentric in any manner), and its too localized to be oiling. I'd like to know what you find on the issue though.
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Old 12-16-2013, 09:16 AM
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To me it looks like a block alignment issue,not the crank (not concentric in any manner), and its too localized to be oiling. I'd like to know what you find on the issue though.
soon as i can get my hands on a piece of stock big enough to machine down to fit in the main bores ill see what i can find
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Old 12-16-2013, 09:21 AM
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Main saddle not parallel would be my best guess.....
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Old 12-16-2013, 09:25 AM
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how much power do u think it takes to start making an oem block flex around?
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Old 12-16-2013, 09:32 AM
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Quote:
Originally Posted by Project89 View Post
i got my old engine torn down and was quite surprised at what i found , engine only has about 3k miles on it , everything looked good except for the main bearings

center 3 lower halves




center 3 top halves



bottom half front and rear main ( flash washed out the copper showing threw but it was dead center on both)


im curious as to what u guys think is the cause
#1 to much power and its trying to run over the crankshaft
#2 not enough clearance
#3 oil starvation
#4 other ?

the rod bearings were pefect , no other signs of distress in the engine except for those 3 lower mains ( even the crank doesnt have a mark on it )
For starters there is evidence of a lot of trash moving with the oil. Some of that could be the top plate being removed from the bearing and circulating with the oil. But that is usually babbit which is pretty soft. Are the rod inserts scratched up like the mains?

The three lower middle inserts wiped but no their matching upper nor the end inserts upper or lower are showing distress in the center of the engine. This can one or more of several causes:

- The lower inserts are different size than the uppers. An example could be the uppers are standard while the lowers are +.001.

- The caps are not correct for their location mixing up the center caps as to location is not that uncommon. This throws the register off for any specific cap.

- The block is warped, but one would think the block is bending upward through the center which is opposite of what one usually finds in such cases where the middle of the block sags a few fractions of an inch.

Bogie
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Old 12-16-2013, 09:38 AM
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Originally Posted by oldbogie View Post
For starters there is evidence of a lot of trash moving with the oil. Some of that could be the top plate being removed from the bearing and circulating with the oil. But that is usually babbit which is pretty soft. Are the rod inserts scratched up like the mains?

The three lower middle inserts wiped but no their matching upper nor the end inserts upper or lower are showing distress in the center of the engine. This can one or more of several causes:

- The lower inserts are different size than the uppers. An example could be the uppers are standard while the lowers are +.001.

- The caps are not correct for their location mixing up the center caps as to location is not that uncommon. This throws the register off for any specific cap.

- The block is warped, but one would think the block is bending upward through the center which is opposite of what one usually finds in such cases where the middle of the block sags a few fractions of an inch.

Bogie
unfortunatly i didnt build this engine but the caps are marked , still doesnt mean they werent mixxed up

the rod bearings had a few gouges but other then that they were perfect
whatever was in the oil was soft because it only left marks in the bearings and not the crank, the crank came out looking like it was freshly polished
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Old 12-16-2013, 01:08 PM
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Micropolishing the crank in the wrong direction will cause an identical effect, on a microscopic inspection you would see polishing create tiny scales on the surface of the crank...this tends to wipe the overlay off typically on the caps only but it can happen to both halves.

The crank needs to be polished in the same direction of rotation as occurs in the engine, I used to work for a certified Ford engine rebuilder and seen this first hand as a number of engines came back with wiped bearings just like yours. The crank grinder who did the cranks for those engines was putting the cranks on the grinder reversed and polishing them backwards.

It took a long time to figure out how it was happening since the problem wasn't obvious and was on a microscopic scale which required a work flow study and review of polishing cork used etc.

What he was doing was grinding the cranks first and stacking them, then chucking the tail later to polish them. Engines turn clockwise so the micropolishing belt would be rotating against the grain of the previous grinding operation if you do it this way.

Usually it doesn't affect clearances until it wipes the copper off and only affects the Babbitt during starts when the crank is touching the bearings, first sign is low oil pressure...next is cold knock...last is a constant tapping making it hard to diagnose.

One more thing to check, it's very hard to prove unless your there when your machinist chucks the crank to polish it.
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Old 12-16-2013, 01:14 PM
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Originally Posted by 4 Jaw Chuck View Post
Micropolishing the crank in the wrong direction will cause an identical effect, on a microscopic inspection you would see polishing create tiny scales on the surface of the crank...this tends to wipe the overlay off typically on the caps only but it can happen to both halves.

The crank needs to be polished in the same direction of rotation as occurs in the engine, I used to work for a certified Ford engine rebuilder and seen this first hand as a number of engines came back with wiped bearings just like yours. The crank grinder who did the cranks for those engines was putting the cranks on the grinder reversed and polishing them backwards.

It took a long time to figure out how it was happening since the problem wasn't obvious and was on a microscopic scale which required a work flow study and review of polishing cork used etc.

What he was doing was grinding the cranks first and stacking them, then chucking the tail later to polish them. Engines turn clockwise so the micropolishing belt would be rotating against the grain of the previous grinding operation if you do it this way.

Usually it doesn't affect clearances until it wipes the copper off and only affects the Babbitt during starts when the crank is touching the bearings, first sign is low oil pressure...next is cold knock...last is a constant tapping making it hard to diagnose.

One more thing to check, it's very hard to prove unless your there when your machinist chucks the crank to polish it.
wow i never would have thought that something like that could be harmful, learn something new everyday thanks for posting that
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Old 12-16-2013, 05:20 PM
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Quote:
Originally Posted by 4 Jaw Chuck View Post
Micropolishing the crank in the wrong direction will cause an identical effect, on a microscopic inspection you would see polishing create tiny scales on the surface of the crank...this tends to wipe the overlay off typically on the caps only but it can happen to both halves.

The crank needs to be polished in the same direction of rotation as occurs in the engine, I used to work for a certified Ford engine rebuilder and seen this first hand as a number of engines came back with wiped bearings just like yours. The crank grinder who did the cranks for those engines was putting the cranks on the grinder reversed and polishing them backwards.

It took a long time to figure out how it was happening since the problem wasn't obvious and was on a microscopic scale which required a work flow study and review of polishing cork used etc.

What he was doing was grinding the cranks first and stacking them, then chucking the tail later to polish them. Engines turn clockwise so the micropolishing belt would be rotating against the grain of the previous grinding operation if you do it this way.

Usually it doesn't affect clearances until it wipes the copper off and only affects the Babbitt during starts when the crank is touching the bearings, first sign is low oil pressure...next is cold knock...last is a constant tapping making it hard to diagnose.

One more thing to check, it's very hard to prove unless your there when your machinist chucks the crank to polish it.
All of this is true as I have seen it on marine engines where one turns backwards.. If the grinder doesn't know, the problem can pop up.. But it will show on all journals..

I would say the caps are wrong or the line bore is way off. The assembler should have noticed the bearing drag.

Heat is what causes the mains to move this much. Not horsepower.
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Old 12-17-2013, 09:27 AM
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Looks like the caps are wrong. Looking at them in the picture, the top main is wore the most. The other 2 are wore more on one side, than the other. That means mis-alignment. If you take the inserts out, and bolt up the mains, you will see that the matting surfaces do not match.
You can also see this on the uppers. Caps wrong.
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