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HotRodMan 07-22-2010 10:09 PM

Excessive main journal wear?
I just recently rebuilt a 232 6 cylinder engine out of a 73 Javelin. I changed the oil and filter every 4000 miles and never ran the engine hard. The engine had about 125,000 miles on it when I took it out of the car. I used standard 10w40 oil.

When I took the engine apart everything looked good except the crankshaft. The front and rear journals and bearings looked real good but the main journals and bearings toward the center of the crankshaft were worn so bad the crankshaft had to be replaced. The rod bearings and cam bearings looked good.

Does anyone have an explanation as to why the main journals and bearings toward the center of the crankshaft were the only area of major wear in the whole engine?

Do you think switching to synthetic oil and a higher quality filter would prevent this from happening in the future?

cobalt327 07-23-2010 12:18 AM

The 232 you had is a seven main bearing engine, and has a good reputation as far as durability goes. If the crank was ground off center on the journals that were damaged, that could account for it. Possibly an imbalance of some sort could have set up harmonics that might have caused some kind of wear problems- but that is admittedly a long shot. Otherwise, given the use and maintenance it was given, I cannot come up w/any other reasonable explanation.

There are some real sharp Rambler/AMC guys here, hopefully one or more will have a comment that will be of some use to you.

Was the crank salvageable or did you just replace it outright?

HotRodMan 07-23-2010 08:17 PM

Cranckshaft was replaced with another unit
The machine shop replaced the crankshaft with another unit, and ground it .010. I think they made the correct decision because it looked really bad.

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