Rod bearing failure

[soaked]

Can a cub oil pump pick up tube get loose, or crack, allowing the pump to suck in air, along with oil? Wondering if maybe foamy oil/vapor cavitation, along with low pressure.
Just thinking out loud

 

[casecollectorsc]

I've seen similar on an engine that had not been run in a long while. I blamed it on acidic oil etching the bearing. Probably wrong, but I thought so. But don't recall only 1/2 the bearing being affected.

Had bearings fail on a 360 engine in my 74 Dodge 4x4 40 years ago that looked like worm wood. Machinist that ground the crank blamed it on the Pennz oil I was using...said it was too acidic and had others with the same problem.

 

[cushman]

Overloaded before it got oil when first started.

Repeated high reving a splash oil system engine to high on startup will cook the bearings in no time.

The cub is a pressure lubed engine,the design does require priming the pump,as it is on the back the cam,way above the oil level.

 

[Dick L]

I am working on a Farmall Cub I just bought and am having to pull pistons. Every piston has a top rod bearing that is delaminating. The bearing appears to be flaking apart, but only on the road side and not the cap side. The rod journals show no signs of wear or damage and look to have either been turned recently in its life or a new crank put in. Someone has overhauled this motor pretty recently (hrs wise anyway) and there is very little wear going on anywhere else. I have never seen a top rod bearing so this and am wondering if this is a manufacturer defect or if someone else can tell me what has happened here.

Thanks
Steven

You need to check the crankshaft journal with a micrometer for both diameter and out of round. then check the bearing insert to see if is the proper fit. That can happen when you do not have proper clearance. I have seen that on the Allis engines on the caps were not shimmed properly. Usually on a slightly out of round rod journal. When the crankshaft (looks good) by a calibrated eye ball.








allis

 

[docmirror]

I vote junk material from new. Bearing material made with pot metal, and that is the side that gets all the pounding.

Mic the journal.
Get the right bearings(std, or under) from a QUALITY source.
Use plastigage to test fit dry.
Lube the journal when new bearings installed.
Pull plugs, and run the engine until there's some modest oil pressure on gauge.
Install plugs, and run in.

 

[John Deere D]

I am working on a Farmall Cub I just bought and am having to pull pistons. Every piston has a top rod bearing that is delaminating. The bearing appears to be flaking apart, but only on the road side and not the cap side. The rod journals show no signs of wear or damage and look to have either been turned recently in its life or a new crank put in. Someone has overhauled this motor pretty recently (hrs wise anyway) and there is very little wear going on anywhere else. I have never seen a top rod bearing so this and am wondering if this is a manufacturer defect or if someone else can tell me what has happened here.

Thanks
Steven

"Previous owner syndrome"
Individual was not aware of Bearing Crush?
Was bearing crush ever checked?
Micrometer used?
Bearing running clearance checked as to manufactures specifications?

Are these Connection Rods designed to be installed in a Specific orientation?
Was the HEAD planed,and or incorrect Pitons installed?
Correct thickness of head Gasket?

 

[13fx]

I highly doubt that bearing crush was ever checked. What I can tell you is that the cylinders were honed improperly, the piston rings were installed wrong on at least 2 cylinders and, the carb wasn't adjusting right. Oh and apparently I must have lost my micrometers in the divorce or the cabin fire because I can't find my set

 

[Dick L]

I highly doubt that bearing crush was ever checked. What I can tell you is that the cylinders were honed improperly, the piston rings were installed wrong on at least 2 cylinders and, the carb wasn't adjusting right. Oh and apparently I must have lost my micrometers in the divorce or the cabin fire because I can't find my set

Details, Details and more details. I rebuilt an engine for an old Allis Chalmers C in 2009 that still starts and runs with power yet. I took photos to show that used parts (in spec) are fine without buying all new. It does not have the information I posted with the pictures. I was short sighted and was not thinking about the future views. Clicking on the engine building above has details on matching the filing the bearing shells that would not be needed on you Cub but gives the importance of checking the fit.
https://public.fotki.com/DickL/allis_chalmers_engi/allis-chalmers-c-st/