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Bearing Clearance

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Old Apr 20, 2008 | 01:19 PM
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Default Bearing Clearance

Getting ready to install the crank in my 383 build. Main bearing clearance with Plastic gauge is between .0015 and .002. To tight? Good to go? Thanks, George
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Old Apr 20, 2008 | 02:12 PM
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that will work. check crank rotation for block or cam interference. check again with rods on. good luck
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Old Apr 20, 2008 | 04:35 PM
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Sorry to disagree, but IMHO anything less than 0.002" is just too tight, and you could end up having to run such thin viscosity oils to keep pressures within reason as to create other problems. You can gain 0.0005" by using 0.001" thinner upper shells in the rods or lower shells in the mains, which would put you in the 0.002-0.0025" range. Don't consider the leftover shells as a waste, rather a small price for doing this right. Oh, and don't mix brands.
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Old Apr 20, 2008 | 08:15 PM
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.001" for every inch of crank journal diameter for a street motor
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Old Apr 20, 2008 | 09:24 PM
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When I read the caps they matched the .002" marks. The crank had wider areas falling between .0015 and .002. How reliable is plastic gauge? Should I have it checked with a set of mic's? Thanks
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Old Apr 20, 2008 | 09:26 PM
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I would not build a motor with plastigauge, you need a dial bore gauge and mics to do it properly
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Old Apr 20, 2008 | 09:55 PM
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Originally Posted by TheSkunkWorks
anything less than 0.002" is just too tight
x2
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Old Apr 20, 2008 | 10:37 PM
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Originally Posted by MotorHead
I would not build a motor with plastigauge, you need a dial bore gauge and mics to do it properly
If you don't have access to these tools, take the block/crank/rods to a machine shop and have them mic it, well worth the added $$
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Old Apr 21, 2008 | 12:08 AM
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Originally Posted by MotorHead
I would not build a motor with plastigauge, you need a dial bore gauge and mics to do it properly
I've built a number of OEM engines over the years with plastigauge and found it an acceptable CHECK for a machine shop that you know can hold a clearance.

For any type of performance engine, it's not enough I agree. As a side note, cheap micrometers and a set of snap guages are better than nothing. In my experience, these work well if kept calibrated. I have a real el-cheapo set I got at a swap meet that I use on my bench, and they've really held up quite well. The economy bore gauges are close enough as well until you get into big-dollar engines. All IMHO, of course

http://www.goodson.com/store/templat...b58fc626f7732e

http://www.goodson.com/store/templat...b58fc626f7732e

http://www.goodson.com/store/templat...b58fc626f7732e
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