How is bearing clearance calculated?
For these reasons, bearing clearances are specified as “vertical clearance” and must be measured at 90 degrees to the split line. The best method of measurement is with a dial bore gage that measures the bearing inside iameter when the bearings are installed at the specified torque without the shaft in place.
What is normal clearance of bearing?
As a general rule, a ball bearing should have an almost-zero operational clearance, while needle, spherical, cylindrical and CARB toroidal bearings should always have some residual radial operational clearance. Radial clearance is the play between the ball and raceway perpendicular to the bearing axis.
What are the bearing clearances for an engine?
Most of these engines are running rod and main bearing clearances of .001? or less, and they are doing it with low viscosity racing oils such as 0W5, 0W30 and 0W50. These racing oils are as thin as water and are highly friction modified.
What are the disadvantages of closer bearing clearances?
One of the disadvantages of closer bearing clearances is that it can increase both bearing and oil temperatures. That’s no problem as long as the bearings and oil can handle the heat, but if they can’t it increases the risk of lubrication breakdown and bearing failure.
What kind of oil do you need for wider bearing clearances?
Wider bearing clearances do require a heavier viscosity oil (such as a 20W50 multi-viscosity oil or a straight 30, 40 or 50 oil). The heavier viscosity oil is absolutely necessary with wider clearances to maintain the oil film between the bearing and shaft so the bearing isn’t starved for lubrication.
How does inertia affect the bearing clearances?
When the piston reaches top dead center on the exhaust stroke, inertia stretches the rod and elongates the bore on the big end of the rod. This, in turn, deforms the bearings and reduces bearing clearances on the lower rod bearing while increasing it on the upper rod bearing.