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Measuring tools for main journals

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Old Feb 25, 2007 | 11:30 AM
  #1  
meyer30's Avatar
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From: Oklahoma
Car: 1992 T/A
Engine: 5.7l 355
Transmission: 4L60
Axle/Gears: 3.42
Measuring tools for main journals

I took my block to a machine shop and he told me my journals were not round. He used some sort of egg shaped tool with rollers on each end. He stuck it in the journal and turned it by hand and said they were .0004" off. I was looking at buying some tools but I can't seem to fine that one anywhere on line. Does anyone know what it would be called? And I already have my rotating assembly purchased so if the main journals have to be line honed will I be able to get different sized bearings so I can use the crankshaft I have? Appreciate the help.
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Old Feb 25, 2007 | 11:51 AM
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F-BIRD'88's Avatar
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From: Ontario, Canada
Car: 1988 Firebird S/E
Engine: 406Ci Vortec SBC
Transmission: TH-350/3500stall
Axle/Gears: 7.5" Auburn 4.10 Posi-Traction
The tool he used is called a Bore Gauge.
To restore the crank main journals in the block.
The machinist will shave a small amount of metal off each main cap. Now the main journals and no longer round and are smaller than stock. Then The caps are reinstalled and torqued to spec. then the main saddles are "line honed" back to a perfectly round hole that is within the stock spec tolerance.
Your connecting rods big hole is reconditioned in a simular fashion. The new bearing is the same outside diameter as stock but if the crank is machined down underside .010-.020" etc then a matching undersize bearing (inner diameter) is used. Both the rods and main saddles holes must be perfectly round and within spec or the bearing will spin.
The block main saddles must also be in near perfect alignment along the length of the block.
generally if the crank is installed in the block with proper main bearing and it will spin freely when spun hard by hand the block main saddle alignment and crankshaft are straight. If the crank will not spin something is out of wack. Could be the crank or the main saddle alignment. Align honing, or in extreme case alignboreing will correct the mains. A bent cast crank is rare and generally trash. (cheap to replace) A $Forged crank$ can be straightened.

Last edited by F-BIRD'88; Feb 25, 2007 at 12:04 PM.
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