rod big end bore help

 
Old 05-23-2017, 02:14 PM
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Default rod big end bore help

so im still very new at this and this may be a ignorant quwstion but do you measure the bore of a rod with the bearings in or out. and i couldnt find what the difference shuold be between it and the crank journal is. rods where 45.16 with bearings and crank was44.90 does this seem normal.
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Old 05-23-2017, 03:28 PM
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Default Re: rod big end bore help

What are you trying to do?
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Old 05-24-2017, 08:03 PM
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Default Re: rod big end bore help

From what I've always seen is you measure the bore of the rod without bearings, then you mic the journal of the crank for the rod, then you ball mic the bearing halves. Do all the math and see that the difference of the rod bore plus bearing halves (bore size minus bearing halves to get actual bore size) minus the rod journal size to leave the remaining number as the clearance that hopefully you are looking for.

Then when you assemble, you plastigauge to verify your measurements were done right for added peace of mind.
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Old 05-25-2017, 06:31 AM
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Default Re: rod big end bore help

Originally Posted by TomCat39 View Post
From what I've always seen is you measure the bore of the rod without bearings, then you mic the journal of the crank for the rod, then you ball mic the bearing halves. Do all the math and see that the difference of the rod bore plus bearing halves (bore size minus bearing halves to get actual bore size) minus the rod journal size to leave the remaining number as the clearance that hopefully you are looking for.

Then when you assemble, you plastigauge to verify your measurements were done right for added peace of mind.
There's pros and cons to each . . . personally I don't like to measure the bearings without being torqued in their bores as you are guesstimating bearing crush. I check the bore with the bearing in with a 3 point inside micrometer and if there's a problem I then grab the dial bore gauge and measure it in several places.

The only real con I know to measuring it this way is potentially scratching the bearings but realistically you could have that problem with anything, not to mention sliding the ball mic around on the surface.
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Old 05-25-2017, 10:04 PM
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Default Re: rod big end bore help

Originally Posted by Pro-SeriesFab View Post
There's pros and cons to each . . . personally I don't like to measure the bearings without being torqued in their bores as you are guesstimating bearing crush. I check the bore with the bearing in with a 3 point inside micrometer and if there's a problem I then grab the dial bore gauge and measure it in several places.

The only real con I know to measuring it this way is potentially scratching the bearings but realistically you could have that problem with anything, not to mention sliding the ball mic around on the surface.
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