Quote:
Originally Posted by rotorwrench
Ford allowed more clearance on the connecting rod big end bearings than they did the mains. My old Mercury manual lists .0005" to .003" for rod big end bearing clearance and .001" to .0026" for main bearing clearances. Side play on the rods is .006" to .020" for two rods on one crank pin.
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Most bearing books have a maximum, and minimum for any given crank. On say a 2" crank, the actual minimum size should be .002 thousandths, and plus, one more .000-50 for a maximum.
If you set a 2" crank clearance to .000-50, or even a .001, the crank when hot will expand about .002 thousandths. So what happens is the crank pushes bearing material out of the way until it has the clearance it wants to get enough oil to the bearing to cool the bearing, and stop its expansion, so why waste bearing material, and taking a chance on smearing a bearing.
Depending on how fast the car is driven, most of the time will determine what the bearing clearance will be when, Cold, or Hot.
Herm.