460 main bearing issues

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460 main bearing issues

Post  achey on July 22nd 2012, 10:11 am

Hey motorheads I am new to this for Big Block 385 seris stuff and have stumbles upon an issue. It is going into a 71 Cheetah MFG jet boat, Berkeley drive. Couple months ago I tore it down hoping to just but a rebuild kit into it. Well...... bored .030 over, balanced, new pistons, marine cam and lifters, crank .010 grind, well you get the picture. Now on reassembly I have an issue with main bearing clearances, rods check out. I have .006 on the mains. what happened I used (Cb816p8-10;11-818p8-10) bearing kit from the "best motor builder at NAPA". I don't know what way to run with this. It is my understanding that bearing sets come in .010 increments. Or is there a .015 set out there? Any advice would sure be appreciated. Thanks to all

Craig

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Re: 460 main bearing issues

Post  LivermoreDave on July 22nd 2012, 10:31 am

Welcome Craig, glad you stopped by!

As to your bearing issue, if possible measure the crankshaft's main journal diameter to validate the dimension. If the dimension is valid, measure the torqued main cap with bearing halves in place. If that dimension seems odd, measure the torqued main caps without the bearing halves. Consult your machinist and/or return the bearings to the store.

Dave.

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Re: 460 main bearing issues

Post  achey on July 22nd 2012, 10:36 am

Thanks Dave, I have already talked to the machine man and he is getting my the grind sheet. I will get the measurements and compare.

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Re: 460 main bearing issues

Post  bbf-falcon on July 22nd 2012, 12:11 pm

Stick the old bearings back in and check what kind of clearance they had. It might give you some insight.

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Re: 460 main bearing issues

Post  Paul Kane on July 22nd 2012, 12:34 pm

Exactly how are you attaining your bearing clearances? With Plastigage? Or via micrometer/bore gauge?

Paul


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Re: 460 main bearing issues

Post  kim on July 22nd 2012, 1:02 pm

also where, there is greater clearance at the cap parting line, less cap to block bulkhead, seems like a no brainer, but some people where never told.

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