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Main bearing clearance

General engine tech -- Drag Racing to Circle Track

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needforspeed66gt
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Re: Main bearing clearance

Post by needforspeed66gt »

Outlaw383 wrote: Thu Feb 13, 2020 9:39 am It was 2.6440 to 2.6450 after the machine work on every journal after machine work.
Did they even cut the caps before honing???? That's WAY WAY over spec, you need to have that fixed so bearing crush isn't compromised regardless of where you can get the oil clearance at with -1 bearing shells.
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Re: Main bearing clearance

Post by BillK »

Outlaw383 wrote: Thu Feb 13, 2020 7:57 am Yes I measured it and micd the crank journal how could I come up with the clearance without doing that ?
Plastigage ?

You would be amazed at how some people check it. I had to ask :)

Outlaw383 wrote: Thu Feb 13, 2020 7:57 am It was 2.6440 to 2.6450 after the machine work on every journal after machine work.
That is pretty ugly :( :(
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Re: Main bearing clearance

Post by Outlaw383 »

Lol BillK yes I know what you mean theres some pretty "creative" folks out there.
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Re: Main bearing clearance

Post by Outlaw383 »

Nate,

No they did not cut the caps. It basically needed one cap cut and the hone run through it and he got it back with all of the mains as I listed.
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Re: Main bearing clearance

Post by modok »

Why is the question about clearance?
Thread should be titled, "bearing loose in hole"
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Re: Main bearing clearance

Post by Outlaw383 »

Not sure why it matters about the title but it came from the fact that I asked the pro builders their thoughts on .004 of clearance between the main bearing and the journal of the crank.
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Re: Main bearing clearance

Post by tenxal »

If the bearings have sufficient crush, why not simply use a set of .001 or .002 under main bearings?
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Re: Main bearing clearance

Post by Steve.k »

I second the above?
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Re: Main bearing clearance

Post by BillK »

tenxal wrote: Fri Feb 14, 2020 7:56 am If the bearings have sufficient crush, why not simply use a set of .001 or .002 under main bearings?
If the bearing bores measure what he stated then the bearings will definitely not have enough crush.
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Re: Main bearing clearance

Post by Baprace »

BillK wrote: Fri Feb 14, 2020 10:04 am
tenxal wrote: Fri Feb 14, 2020 7:56 am If the bearings have sufficient crush, why not simply use a set of .001 or .002 under main bearings?
If the bearing bores measure what he stated then the bearings will definitely not have enough crush.
BillK, has it correct.
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Re: Main bearing clearance

Post by Old School »

Something is not adding up. The main diameter specs from GM are 2.6406-2.6415 range. If we use the 2.6440 to 2.6450 you have and use the median main diameter of 2.6410 we have .003-.004 loose on the main bore. Yet you have .004 clearance with the bore way out of specs.

If the block is corrected to 2.6410 then your clearance will be .00-.001. Is that correct? What was your clearance before you aligned honed the block? Sounds like your crank may be on the high side.
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Re: Main bearing clearance

Post by Outlaw383 »

Thanks for the help everyone he got another block and had the caps touched up and a hone run through the mains (By a different machine shop) Put the main bearings in it and we now have right at .0025 to .0028 clearance. He understood what I was saying about not trusting the old block and it's getting close to the season starting so he said he didnt have time to straighten the other one out right now so we will deal with it on another build.
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