Bent crankshafts

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Model T Ford Forum: Forum 2011: Bent crankshafts
Top of pagePrevious messageNext messageBottom of page Link to this message  By Val Soupios on Monday, December 26, 2011 - 06:49 pm:

While redoing the motor in my '14 I found that the crank was sprung .007. I was able to get it back to less than .001 but as an afterthought I checked three other cranks that I have standing on end in my shop. The journals on all three measure up standard and they are not out of round yet one of them is sprung .010 and the other two are sprung .007. Are all T cranks bent? The crankshafts are so flexible that you can move the center main .004 with just a moderate pressure from one finger so I am wondering how much of an issue it is if the crank is brought back into alignment when the center main cap is on and it rotates smoothly without binding on what would be the high spot.


Top of pagePrevious messageNext messageBottom of page Link to this message  By les schubert on Monday, December 26, 2011 - 07:29 pm:

Val
.007" which I am assuming is the total dial indicator reading actually means your crank is only .0035" bent. I would not have any concern about it.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kerry van Ekeren. (Australia) on Monday, December 26, 2011 - 07:53 pm:

You can only have run out within the oil clearance, 1.5 thou, anymore then the crank will pull babbitt.


Top of pagePrevious messageNext messageBottom of page Link to this message  By les schubert on Monday, December 26, 2011 - 09:47 pm:

Kerry
I must disagree. As he indicates, moderate pressure with his hand takes all the bend out. Consider the loads when the engine is running and this is greatly less. So no real problem.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kerry van Ekeren. (Australia) on Monday, December 26, 2011 - 10:30 pm:

Well, if still using the flogged centre bearing that matches the run out in the shaft I agree, vibration would be the issue then and eventually a snapped shaft, but if running a new set of babbitt I think would be a problem from get go.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Val Soupios on Tuesday, December 27, 2011 - 10:43 am:

For what it is worth, before straightening, when the crank was set in the block with only the front and rear main caps installed the crank would bind at the center main. With the center main cap also installed there was no binding which I assume is a result of the cap pulling the crankshaft back into alignment. Once the crank was straightened there was no binding in either case and bluing the mains showed better than 75% coverage at all three journals.


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