Busted rear mains/crank

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Model T Ford Forum: Forum 2014: Busted rear mains/crank
Top of pagePrevious messageNext messageBottom of page Link to this message  By Allan Richard Bennett on Sunday, March 02, 2014 - 10:03 pm:

In a recent thread mention was made of a crankshaft breaking and taking out the rear main bearing. I wonder whether this is the correct sequence of events. I know of three instances where the rear main has been broken/crankshaft broken in pre 1913 blocks. Then I purchased a 1912 bare block and prior to rebuilding it it was chemically cleaned. On not so close examination extensive cracks were found extending across the rear main bearing web. It was about to break right out. Certainly, if the engine had run much longer, it would have broken and probably taken the crankshaft with it.

On a later 1923 block which broke a crankshaft between cylinders 1 and 2, I noticed similar cracks in the rear main webbing. I broke this main out of the block and it was clearly evident from the polished surfaces of the cracks that the the rear bearing was 'working', and would have failed had not the crankshaft beaten it to the punch.

I mention this for two reasons.

Perhaps we should be more diligent when inspecting blocks for re-building, paying close attention to the rear main webbing.

Secondly, if this unfortunate occurrence happens to you, check that perhaps it was the rear main letting go which took out the crankshaft.

I would appreciate your thoughts/experiences gentlemen.

Allan from down under.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ted Dumas on Sunday, March 02, 2014 - 10:38 pm:

Your point is well taken, but on my 24 I don't know which came first, the chicken or the egg. I have a crankshaft that I found in a field that is cracked between 3 and 4 at the same place my 24 crank failed.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Les VonNordheim on Sunday, March 02, 2014 - 11:23 pm:

I have a 17 block that had the rear main web broken out. It was weld repaired using high nickel arc rod. If it were welded using cast iron rod the old way.....I would run it. Otherwise, it's a nice looking block but I would not chance it.


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