Lycoming crankshaft bearing dimensions?

[Valentine]

I want to know crankshaft bearing diameters for O-320 & O-360 engines.
What I am trying to discover how these engines get converted to 200+ hp engines without creating dangerously over stressed cranks.

[deek]

The bigger issue is the length of the nose main bearing. Gyroscopic loads on the nose bearing, and the bending of the crank during acro with heavy props spinning at high RPM are the conditions to worry about.

If using a counterweighted crank then there are other, more complex issues at hand.

[jrs14855]

Most of the failures on Lyc cranks have been flange failures. Some of the machining on the transition radius to the aft side of the flange is very poor quality.