Do I need to turn or polish my crank? - Hot Rod Forum : Hotrodders Bulletin Board
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Old 07-21-2008, 08:29 PM
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Do I need to turn or polish my crank?

A friend of mine just gave me the rotating assembly out of a ford racing crate motor he purchased and turned into a 331. He put about 15k miles on the original assembly before pulling it out. After going over the crank most of the journals are still smooth but a few have some small scratches from wear. None of the scratches are really large enough to catch a thumbnail in but their not perfectly smooth either. How do I know when I can get away with just polishing the crank and when do I need to turn the crank? I will obviously replace the bearings, but I would like to get away with not having the crank turned if possible.

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Old 07-21-2008, 08:43 PM
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mic the crank, if it mics good, clean and polish, mic again. small scatches won't cause any problems.

sam-missle
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Old 07-21-2008, 09:13 PM
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Quote:
How do I know when I can get away with just polishing the crank and when do I need to turn the crank?
Quote:
mic the crank
Couldn't be said better.
ALWAYS MEASURE!
ALWAYS CHECK - EVERYTHING.
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Old 07-21-2008, 09:20 PM
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whats an ok bearing clearance on a ford small block?
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Old 07-22-2008, 06:52 AM
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polishing a crank

If it mic's OK, I polish my with large brown paper grocerey bag strips (if you can find a brown paper bag now days. Just cut it into strips narrower than the throes of the crank. I have remover-ed small rust spots that aren't bad with it.
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Old 07-22-2008, 07:01 AM
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An old leather belt works great for polishing too.
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Old 07-22-2008, 08:04 AM
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Da south,
do check out the Knowledge Base link at the top of the page for any motor's specs....
ex:
http://www.hotrodders.com/kb/ford-engine-tech
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Old 07-22-2008, 11:41 PM
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Ok, I looked in the knowledge base and have done a good bit of searching looking for wear specs, or tolerances on a sbf and I cant really find much. I can find the original part specs, but can't find anything that says what wear is within normal specs and what is excessive and must be replaced. Can anyone guide me in the right direction?
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Old 07-23-2008, 04:01 AM
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Quote:
Originally Posted by DaSouthWon
whats an ok bearing clearance on a ford small block?
For a street motor.....
0.001"/0.002" on the rods, shoot for 0.0015"
0.0015"/0.0025" on the mains, shoot for 0.002"
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Old 02-24-2014, 10:38 PM
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thanks to all who replyed ....

has anyone tried a ruby stone or a arkanasaw stone to micro polish minor imperfections too small for your finger nail to catch and my crank is nitrited on mains and journals I like the paper bag thing and the leather belt thing. I found out about this site from a friend that I met in a post. those stones are used by mold makers and tool makers to polish mold parts. Im a tool maker 32 years trying to do things by my self if I can . thanks again for all who take time to talk to me and share there knowledge.........
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