Evaluate my crankshaft main bearings

pburchett

Member
Since this is my first tear down I was surprised to see the wear pattern on the bearings. Anything I need to look for when I put it back together?

The front is seemingly wearing good.
mvphoto32922.jpg


The middle has worn through the coating…
mvphoto32924.jpg


The rear has worn through the coating near the oil passage.
mvphoto32926.jpg
 
So have you measured the journals for diameter and out of round? My guess is that the one with the copper showing is out of round. The only way to know for sure is to measure it. If any of the journals are out of spec you will not be able to get proper clearance. With out proper clearance or out of round journals you will get to redo them in a short time. If you run the engine that is.
 
In my opinion, 'Ideal wear' would be three different bearings that look like the top picture.

Looking at pictures doesn't tell much. You need to get the crank measured with a micrometer. A good engine shop should be able to do the job for you and tell you how badly the crank is worn and if it needs to be re-ground under size. And they probably can help you with bearings as well.
 
what engine is this? and what do the rods looks like? could have plastiguaged those to get an idea of clearance. and hrs or years since last overhaul. what are you doing to this engine? nothing abnormal.
 
640 Ford 134ci red belly engine. Been in the family since 1979. Nothing done to it since then. Thought it was time to freshen it up a little. Started to fix the rear main leak and re-ring it. Found the bearings in this condition and didn't know if this was a sign of a bad issue. Got everything apart and semi cleaned up. Will put the plastigauge to it and get some specs soon.
 
moonlite, I agree. Looks very typical as for wear patterns, exceptionally clean.

Usually there will be circular scratches and embedded particles. It has been well maintained.

Main bearings never wear all the same. Variances in machining, alignment, clearances , balance all create varying wear patterns. Usually the front bearing will be worn on top because of the belt pulling upward. The middle toward the bottom because of downward pressure, the rear will be either downward or wallowed all around if there was a balance problem.

Still the crank needs to be checked with a micrometer just to be sure, but I suspect it will go back standard looking at the bearings.
 
They should all look the same id the block checked /
line bored and the crank checked / polished turned .
When I tore down my 66 4020 in 2003 all the
bearings were stamped 1966 and all looked like first
one in your picture
 
I would guess the one showing the wear is the bottom. I would spin a set of new bearings in and plasigage them. Then the rods the same way. Unless you have reason to need more done. Typical wear pattern for mains. For the rings check your bore taper and then go from there. I would check the bore taper before the bearings in case you have to have the block bored or sleeved.
 
Thanks guys.

Since I am in unknown territory with my lack of experience I am unable to evaluate the internals of the engine.

I truly appreciate the comments and help as it guides me with this project.
 

They all look like normal ware to me and its good you went for the kill are you may have never stopped the leak from a worn crankshaft... A crank kit will settle the issue just make sure you check and clean the new crank...

Make sure you leak test the rear seal before you nail the pan on...



https://forums.yesterdaystractors.com/viewtopic.php?t=1046518&highlight=soap

Read up on rear seals they are a booger and will eat your lunch...

https://forums.yesterdaystractors.com/viewtopic.php?t=1311710&highlight=rear
 

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