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Old 06-01-2017, 09:51 AM   #1
OC_Nooby
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Join Date: Feb 2012
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2003 WRX w STI V8

Default Crank roundness, quick question

Hey,

When checking to make sure the crank is not out of round do you only measure the center main journal or all of them?

I measured all (2 bearings on the case halve) and worst was 0.0009 #4 or 5 (if I recall correctly)

Thanks
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Old 06-02-2017, 07:22 PM   #2
OC_Nooby
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Guess its not so quick.

Spec is 0.0014
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Old 06-02-2017, 09:28 PM   #3
jw4902
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I know just enough to screw it up, but from what I've read each journal has to be measured twice at ninety degrees from the first measurement. But I've also read that very few reuse Subaru cranks because factory new cranks are such a bargain for the vast majority of uses. Its cheaper than having a good machinist bring it up to snuff. I've also heard that U.S. made V8 motors are not that way. Good luck.
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Old 06-02-2017, 11:42 PM   #4
OC_Nooby
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Quote:
Originally Posted by jw4902 View Post
I know just enough to screw it up, but from what I've read each journal has to be measured twice at ninety degrees from the first measurement. But I've also read that very few reuse Subaru cranks because factory new cranks are such a bargain for the vast majority of uses. Its cheaper than having a good machinist bring it up to snuff. I've also heard that U.S. made V8 motors are not that way. Good luck.
One is to measure the journal, another is to measure the journal while rotating the crank. Make sure it's not bent. My previous crank was at 0.0030! Weird as it was in my running car, I think something may have happened at the machine shop. But I could be wrong (was good prior to the old build).

Just wanted to know if you measure the middle journal or all, I did all which is within spec.
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Old 06-03-2017, 07:20 AM   #5
jw4902
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Yes I think main journal condition (round or not, smooth, etc) and crank straightness are different things. I'll check the faqs and do some research to see what I can find. It seems like either a good machinist okays the crank after inspection or you buy a new one. But then the block has to be declared okay or line-bored or line honed, so I guess that's why we have professional engine builders. But I like to learn about our cars so I'll check into this and pm you in a week or two.
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