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Old 10-09-2010, 09:10 PM
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Tapping the Back of Crank

I was wondering what is the process when a builder hits the back of a crank with say a small hand-held type sludge hammer. Just wondering because I've seen this act more than once and was just wondering what exactly what this was accomplishying.

If you are a little lost, the short block is built, then the builder hits the crank a few times. Does this help the parts settle better or something?

I know silly question, but I had to ask. I've seen my builder put a 2-3" long steel sleeve on the end of the crank and wack it a few times along the outer edge (diameter) of the sleeve. I have also seen an iron block tapped on the back a few times.

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Old 10-09-2010, 09:22 PM
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some people feel that doing that helps seat the trust bearings on the crank. wether the method does anything good, anything bad, or anything at all seems to still be quite a debate. some say it hurts, some say it helps, some say it doesnt make a difference whatsoever.
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Old 10-09-2010, 09:24 PM
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crank and hammer

It is to center the crank before checking the crank end play.
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Old 10-09-2010, 09:28 PM
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If the engine being built does not have a pin or other method of locating the crank main thrust bearing (some Chevrolet). The thrust must be set by tightening all main bearing caps to spec except the thrust bearing. The thrust bearing cap is tightened enuff to set" the cap. Then the crankshaft is moved back and forth to properly locate the thrust. Then torqued to normal specs..

This method can also be used to increase/decrease the thrust clearance.

To try this after the mains are torqued/engine assembled, is a waste of time.
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Old 10-09-2010, 09:29 PM
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wouldnt it be a bad thing if you had to slam the crank with a lump hammer just to get it to move enough to check end play? shouldnt the crank move fairly easily, both rotating, and side to side? the reason i ask is ive never heard of this before and i wonder why would you need the crank centered to check end play?
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Old 10-09-2010, 09:30 PM
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I've seen this done with the motor completely assembled.
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Old 10-09-2010, 09:32 PM
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Builder evidently is not fully aware of the proper procedure
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Old 10-10-2010, 07:40 AM
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Quote:
Originally Posted by BOBCRMAN@aol.com
If the engine being built does not have a pin or other method of locating the crank main thrust bearing (some Chevrolet). The thrust must be set by tightening all main bearing caps to spec except the thrust bearing. The thrust bearing cap is tightened enuff to set" the cap. Then the crankshaft is moved back and forth to properly locate the thrust. Then torqued to normal specs..

This method can also be used to increase/decrease the thrust clearance.

To try this after the mains are torqued/engine assembled, is a waste of time.
Both of the performance engine building videos I have show it being done the way and for the reasons Bob explained.
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