bearing clearance

hi

but how can you know how much measure clearance do you need please? or is it a standard clearance size? the measurement of bearing clearance

The rule of thumb is that you need 0.001 inch of clearance for every inch of crankshaft journal thikness. For instance if your main journal is 3 inches you would need 0.003 inch bearing clearance on performance engine bearing in mind that it depends on the power level per cylinder. The more power you get per cylinder the bigger the clearance should be as the crankshaft journals bend out of shape because of the torque they face...