Ok... When the engine is running at low rpm and the throttle is wide open, AND the engine cannot GAIN rpm.. The engine gets the largest possible explosion trying to push the rod into the crankshaft.. BUT the crank is not speeding up.. due to the? hill? large tires? tall gearing? heavy tow load? So the rod is giving the most push and choking out the lubricating oil.. over and over again.. never having relief for cooling from a gush of cool oil into the bearing surfaces. Or a lessening of the throttle position which would allow less torque on the rod bearings.
I learned this with that new 63 Ford and a mobile home. Changing the gear ratio alowed the little engine to turn more rpm at less throttle.. which equaled less torque on the rod bearings.
New bearings were installed at 2500 miles, 4500 miles and then never again.. all the time towing the same mobile home.
Big Jim
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