Like to hear thought on main bearing crush when its out a .0002 loose?

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user-23911

Re: Like to hear thought on main bearing crush when its out a .0002 loose?

Post by user-23911 » Mon Apr 09, 2018 6:07 am

If you look up the rate of expansion with temp, you might find that measuring 3 inch diameter at 0 deg C then measuring again at 20 deg C will give a change of 0.00066 inch.Maybe a bit less depending on the material.

So that's 3 times your error over 20 deg.
Or to put it another way a change of 7 or so deg will give a similar error to what you've measured.


Is it worth worrying about?


If you like to play with fancy tools you need to play with them in a controlled environment.

user-23911

Re: Like to hear thought on main bearing crush when its out a .0002 loose?

Post by user-23911 » Mon Apr 09, 2018 5:25 pm

Maybe I worked it out wrong?
Would anyone here know?

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Re: Like to hear thought on main bearing crush when its out a .0002 loose?

Post by Warp Speed » Mon Apr 09, 2018 6:00 pm

joe 90 wrote:
Mon Apr 09, 2018 5:25 pm
Maybe I worked it out wrong?
Would anyone here know?
It's your story..........

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Re: Like to hear thought on main bearing crush when its out a .0002 loose?

Post by MadBill » Mon Apr 09, 2018 6:08 pm

The thermal expansion rate of steel is 7.2 ppm F., so a 3" diameter specimen heated from 32 to 68° F. (0-20° C.) will expand by (7.2 x 3 x 46)/1,000,000, or almost exactly one thous.
Felix, qui potuit rerum cognscere causas.

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Re: Like to hear thought on main bearing crush when its out a .0002 loose?

Post by NXBOY » Mon Apr 09, 2018 6:22 pm

I asked more then one question at first [-X and for the record I was going to run it like it was. I do realize that most people I know just make sure mains are within spec and trust the Bearing company for crush. I should of just said was a tiny bit out of spec and I always thought and read on the big 3 inch mains with fairly high RPMS and nitrous use, you need all the crush you can get. I always in past been fine or had aligned bored and been in the middle of the eight 10 thousandths window it gives. I always thought going to tight side from loose side of spec, would make some difference on holding bearing , understand align honing isn't as good as Boring and will be looser /bigger the worst the bore is out. So sound like alot of you guys are saying close to spec is good enough. I AM NOT worried about .0002 , on the edge of spec would be no difference. Atleast I learned to measure crush and thats better then trusting bearing company.

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Re: Like to hear thought on main bearing crush when its out a .0002 loose?

Post by statsystems » Wed Apr 11, 2018 6:34 pm

Run it. If .0002 kills it there is something else wrong.

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Re: Like to hear thought on main bearing crush when its out a .0002 loose?

Post by superpursuit » Wed Apr 11, 2018 10:46 pm

statsystems wrote:
Wed Apr 11, 2018 6:34 pm
Run it. If .0002 kills it there is something else wrong.

I've got to agree with this. :D

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Re: Like to hear thought on main bearing crush when its out a .0002 loose?

Post by gnicholson » Wed Apr 18, 2018 5:27 pm

Heres another question: how much does removing and reinstalling a visually perfect used main bearing affect crush? Or put another way ,is it safe to reuse?

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Re: Like to hear thought on main bearing crush when its out a .0002 loose?

Post by pamotorman » Wed Apr 18, 2018 5:35 pm

gnicholson wrote:
Wed Apr 18, 2018 5:27 pm
Heres another question: how much does removing and reinstalling a visually perfect used main bearing affect crush? Or put another way ,is it safe to reuse?
i reused rod bearings if they looked good when doing a re ring and never had a problem

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Re: Like to hear thought on main bearing crush when its out a .0002 loose?

Post by cgarb » Wed Apr 18, 2018 6:04 pm

If the bearings look good, and still snap into their respective bores like they should...I reuse them all the time. I had a set of coated bearings I ran on 2 different sets of rings...4 seasons of brackets in my 355. Just started to take the coating off on the last time I pulled it apart so I tossed them.

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Re: Like to hear thought on main bearing crush when its out a .0002 loose?

Post by IDT-572 » Wed Apr 18, 2018 6:05 pm

High side is the max allowed factory tolerance. .0002 over that is fine, your talking fly crap in the pepper shaker.

Stock block 460 Fords I build with Chinese 4340 cranks (Scat, Eagle) I always line honed to 3.193 high side. The cranks are ALWAYS big and now the main bore is true and with main oil spec at .0034 to .0036 with a standard bearing, they live no problems.

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