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Extra Clearance Bearings, Use One half, Top or Bottom?

General engine tech -- Drag Racing to Circle Track

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n2omike
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Extra Clearance Bearings, Use One half, Top or Bottom?

Post by n2omike »

With extra clearance bearings, I know you can use only one if only half a thou is needed. I believe I remember it being said it's best to use the extra clearance bearing in either the top or bottom... but cannot remember which.

So, do I put the looser bearing shell in the top or bottom... or does it really matter?

Thanks!
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Re: Extra Clearance Bearings, Use One half, Top or Bottom?

Post by engineguyBill »

Bearing manufacturers recommend installing the thicker bearing shell in the lower position for main bearings and the upper position for rod bearings. However, I and many others have installed the thicker shells in the upper position main bearing location and the lower position of the connecting rod with no problems.
In summary, I recommend going by the bearing manufacturer's recommendations . . . . . . .
Bill

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n2omike
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Re: Extra Clearance Bearings, Use One half, Top or Bottom?

Post by n2omike »

engineguyBill wrote: Thu Feb 06, 2020 11:41 am Bearing manufacturers recommend installing the thicker bearing shell in the lower position for main bearings and the upper position for rod bearings. However, I and many others have installed the thicker shells in the upper position main bearing location and the lower position of the connecting rod with no problems.
In summary, I recommend going by the bearing manufacturer's recommendations . . . . . . .
Thanks for the reply, Bill. I appreciate it!
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Re: Extra Clearance Bearings, Use One half, Top or Bottom?

Post by BlitzA64 »

I have used them both ways myself, never saw an issue either way on disassembly. I guess like Bill said go with the bearing mfg suggestion, I always saved the extra bearings to use rather than use half a set then throw away the rest
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Re: Extra Clearance Bearings, Use One half, Top or Bottom?

Post by needforspeed66gt »

BlitzA64 wrote: Thu Feb 06, 2020 1:29 pm I have used them both ways myself, never saw an issue either way on disassembly. I guess like Bill said go with the bearing mfg suggestion, I always saved the extra bearings to use rather than use half a set then throw away the rest
Yep - I've done this too many times to count, never a problem and they look exactly the same on teardown.
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Re: Extra Clearance Bearings, Use One half, Top or Bottom?

Post by modok »

I was taught to use the thinner shell in the cap.

I can imagine some situations where the reverse would work better, tho it would be a rare case.
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Re: Extra Clearance Bearings, Use One half, Top or Bottom?

Post by BILL-C »

We have used the thinner halves in either location in several hundred race engines with no issues.
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Re: Extra Clearance Bearings, Use One half, Top or Bottom?

Post by PFC1 »

Maybe the bearing companies recommend only using certain halves in certain locations so you'll waste more bearing/thus they sell more. Just a thought. I regularly use them both ways w/o issue.
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Re: Extra Clearance Bearings, Use One half, Top or Bottom?

Post by EDC »

Would it really make a difference?

As long as the "thick" shells were installed on one side and the "thin" on the opposite, how would the crank/block know?

We're talking a .0005" delta?
"Quality" is like buying oats. You can pay a fair price for it and get some good quality oats,
or you can get it a hell of a lot cheaper, when it's already been through the horse.

Nil Satis Nisi Optimum

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