Сonnecting rod bearing damage.

oneman

Member
Hi guys, I found a problem, on 2 different engine, we got severe bearing damage. And they are the same.
damage in the upper of the connecting rod, I think this is the most loaded place, but why did it start to crumble?

The engine were used by different people, with different components. But why did it come about?
 

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flattop1

Dawg 89
although oil type and viscosity is a concern . with the current oils , my opinion is that is not as much of a concern as it was say in 1970 .

Ignition timing over advanced with a high load .
contributing factor out of round with poor surface finish .
tight clearance and debris can not be ruled out .
 

oneman

Member
We are using Castrol racing 4T 10w30 we change the oil every 1.5-2 moto hours.
This is the wear that has occurred during a run of 6-7 motor hours.
Bearing clearance is acceptable, as indicated in the ARC connecting rod manual. I specifically measured it before installation.
Engine speed 8000-8500.
I have an ignition advance of 28-30, on one engine it is a key with an offset of up to 30. And on the second there is a PVL flywheel.
We use a standard 54mm clone crankshaft.
 

oneman

Member
29.965 -29.950mm

crankshaft journal size is normal, within acceptable limits no scratches or damage.
 

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