Chicken and Eggshells

The engine has been torn completely down now, and the bottom end has two big problems. The #3 main bearing is completely wiped out, which explains the low oil pressure. The crankshaft is also bent, which is odd since it was new this spring and we had several strengthening and blueprinting processes performed before it was installed.

So which came first? Did the bearing collapse, allowing the crankshaft to flex too much by taking away its central support? Or did the crankshaft bend (or crack) and then destroy the bearing? A chicken and egg problem, but at least the connecting rod didn’t cross the road this time.

The crank and the engine block will have to be checked for cracks and thoroughly measured first. A crack in either one would answer the question while permanently retiring that part. Accurate measurements should tell us if the crank can be repaired and if the block can be reused. It would be disappointing to say the least to have to scrap the second engine in two seasons.

(In case you’re picturing a crankshaft folded in half or twisted like a pretzel: It doesn’t take a very dramatic curve to render a crankshaft unfit for use. It still looks like a good crankshaft to the unaided eye. To check for straightness, you place the crank in the engine so that it is only supported by one main bearing at each end. A very precise measuring tool is put in contact with the center main bearing journal on the crankshaft, and the crank is slowly rotated. In this case, the center main bearing journal is 0.0025” off center. Not exactly a banana, but that’s much worse than the maximum allowed 0.0005” measurement.)