Noble/Rossion Engine Failure

Inn our last story, we received the results from the oil analysis for the Noble M12 3.0 L Ford Duratec V6 motor. Now that we had the pistons, rods, and crankshaft disassembled, it was time to look at the main upper and rod bearings.

Common Causes of Engine Failures:

• Broken connecting rods and/or crankshaft (catastrophic)

• Crankshaft flex

• Detonation (fuel pre-ignite in the engine’s combustion chamber)

• Oil starvation/Improper lubrication

• Spun rod or main bearing (metal shavings in engine’s oil)

We consulted with a bearing specialist from a reputable bearing manufacturer. The upper main bearing appears to 

show a heavy amount, but still leaving the coating intact at the bore reliefs (parting lines) which should not carry

significant load. Similarly, looking at the rod bearing, it appears to still have the machining marks in certain areas from machining the substrate before overlay plating. Typically, when there is some sort of oil starvation, the overlay will have some darkening from it overheating (this is not the case).

After a little bit of more investigating, we contacted a consultant for NASCAR. It was determined that high cylinder pressures or high RPMs can cause wearing on the edges of the bearings (metal - to - metal)  instead of the front or center of the main bearings. As a result, crankshaft flex is the cause of failure for this engine. 

Note: The bearing furthest away from the oil feed/oil galley will look worse than the others if there is low oil pressure.