bearing failure

[rarebit]

what would cause rod bearings to fail? only two rod bearings went out. i figured while i was in there, might as well replace all the bearings. the rod bearings wore just a little bit down to the copper underneath. the engine was making a terrible racket. the crank looks fine.

maybe an oiling problem? i change the oil every 3k with synthetic. 2 cranks broke in this same block. i wonder if the block is messed up causing the bearing failures. any ideas?

 

[bezerk]

it''s probberbly a failure in the block.
i had an bearing failure also.

let's explain:

The crankl has an oilcircuit, wich lubricates all the bearings,
if one bearing has an to low clearance, the crank or rod will eat itselve thru the bearing causing an to much clearance.
than oilpressure will be lost, causing an lubriaction failure to the other bearings.

so just throw your block away!
there is a big fat chance that some material was eating out of the maincaps/ main......(sorry don't'know how you call it, but you get it)

good luck

 

[sytydvr]

u can use the block again just need to get it line bored and u really need a new crank make sure you get the oil feed holes chamfered

c ya

 

[bezerk]

u can use the block again just need to get it line bored

if there was a bearingfailure, it is real possible that the bearing spun, scraping material away from the block, how would you bore that??
maybe you know of some new method to do that, but my geuss is that it isn''t worth the risk to try this after 2 failures

 

[myclone]

Rod bearings can fail for several reasons.

1. Lubrication problem which can be caused by any one of the components in the oiling circuit failing or not in spec. Everything from a stuck bypass at higher RPM to a piece of casting flash breaking loose inside the oil gallay(s) and making its way to the pump or plugging a oil supply hole.

2. Excessive RPM. The stock rods arent designed to sustain high RPM at all so if they are subjected to it the big end can and will flex causing the rod bearing clearances to close up. This will cause the rod bearing to over heat and/or sieze on the crank journal which spins the bearing.

3. Milage.. An unmaintained oiling system with a lot of miles will be full of sludge and other nastyness that will eventually cause one or more bearings to fail.

4. Detonation.. Detonation is essentially transferred to the bearing through the rod which can overwhelm the oil film causing metal to metal contact between the bearing and crank journal. Excessive detonation and/or extended periods of it will eventually cause one or more rod bearings to be destroyed.

You asked about reusing the crank. Thats not a problem IF the crank journals are checked for proper dimensions and the journal surfaces are refinished to the proper spec. This can be as simple as a polish for a mildly damaged crank all the way up to welding new material on and regrinding for a severely damaged one. At NO time should you try to use a crank "as is" after a bearing has spun IMO.


bezek,

Spun bearings do not mean a block can no longer be used every time. All that is done to correct the problem if a main bear has spun and damaged the block is the main caps have a few thousandths taken off the block mating surface which essentially makes them shorter. When these are bolted on you no longer have a "round" hole but an oval one so what a machine shop does is bore that now oval hole out until it round again so the main bearings are positioned properly. The process is called "line boring" and is done on a regular basis by most any machine shop. Also, the rods get the same treatment for the most part to rebuild the big end when a rod bearing has spun damaging the rod(s).

Thats an EXTREMELY short version of whats done to correct the proplem but I think you get the idea.

 

[rarebit]

the bearing wasnt spun. two of the rod bearings (not the main) had worn down to the copper underneath. the bearings came easily off the crank. i replaced all the bearings by removing the third member stuff without pulling the engine. the crank appeared to be fine. it did not have any grooves or visual wear. i simply re-installed new bearings.

after replacing the bearings, the horrible scraping sound has gone away. however, the engine doesn't sound like it did before. there's a definite metallic sound coming from the engine area that comes on at off idle/cruise. this leads me to believe something is wrong with the crank. right now i feel like i'm driving a time bomb around. i can't afford to re-build at the moment.

apparently the oil feed line from the side of the block had sprung a leak. the engine was down about 2 quarts of oil in about 4-5 days. i did not notice the leak until i noticed the noise the engine was making. could being down two quarts cause a bearing failure? the oil level was not an issue with the two cranks that broke.

also, does oil pressure have anything to do with crank lubrication? could oil pressure failure cause the rod bearings to fail?

 

[4C FED]

Here's some good info on bearing failures:

http://www.engineparts.com/motorhead/techstuff/bearingfailures.htm

 

[rarebit]

Here's some good info on bearing failures:

http://www.engineparts.com/motorhead/techstuff/bearingfailures.htm

look at the "Distorted Crankcase" pic. two of the bearings look like the 2nd from the bottom in the right column. the wear patch isnt as big. the wear doesnt extend to the edges of the bearing. the wear is pretty much isolated to the middle region of the bearing but not exactly in the center. it's more offset to once side of the bearing. much like the wear in the "Oil Starvation" pic, but without the dark discoloration. the wear on mine are a shiny copper color. not dark. this goes for two of the bearings only the rest look fine.[/url]

 

[bezerk]

About the Line bore:

i know that you can get the oval, round again, but my thinking is that the material between the crank and the mains would get way to big.
and the bearing material beeing more softer than the mains, would cause a oval hole in the bearings again becuase of the rotation of the crank isn''t quite ideal.

but that is just my geuss.

 

[GEN3Typhoon]

About the Line bore:

i know that you can get the oval, round again, but my thinking is that the material between the crank and the mains would get way to big.
and the bearing material beeing more softer than the mains, would cause a oval hole in the bearings again becuase of the rotation of the crank isn''t quite ideal.

but that is just my guess.

HUH? Are you serious?

They line bore only the mains. If you plan to use main studs in your rebuild the shop will need those also when they line bore it. The line boring is done ONLY on the main journals... then each of the rods is checked and resized. This is common practice.. and I will tell you that if you have ANY bearing issues and you don't tear the motor down and replace all the rod, main and cam bearings... be sure you keep the number to a wrecker service with you EVERYWHERE you go. It is just a matter of time before your motor dies... all that metal went somewhere.

 

[Sy769]

About the Line bore:

i know that you can get the oval, round again, but my thinking is that the material between the crank and the mains would get way to big.
and the bearing material beeing more softer than the mains, would cause a oval hole in the bearings again becuase of the rotation of the crank isn''t quite ideal.

but that is just my geuss.

Not flaming you but there is no need to throw out "guesses" when there are plenty of people on here that can answer the question correctly.

As everyone else said line boring of blocks is common and essential when adding 4 bolt mains or repairing a block that has spun a main bearing.
You can even repair a connecting rod that has spun a bearing if it is not to bad. I wouldn't recommend rod repair for any type of performance engine but I do have a Olds Cutlass that has a repaired rod and has been driven daily for years and over 100k since that repair.

A bearing failure in most engines means you should pull the engine and check the crankshaft and all friction surfaces for wear with a micrometer and check for cracks bent rods etc. Especially in our applications there is NO room for error. Even though a journal looks fine there is a underlying reason for the wear and problems not visible to the naked eye.

I've done my share of shade tree rebuilds but they were all low rev old tractors and and equipment. Any performance application will eat itself in short order if anything is wrong.

 

[bezerk]

Atleast, when i throw in a geuss, i get the information that i am wrong.
So thanks for the information, i didn''t know that it was possible/save to do something like that.

look, here in Europe i i never heard about annything like that.
but here we use more throw away engine''s as i may call them.


Sorry for my geuss, and thanks for the info.