Newbie question on cranks

[Ramon]

Sorry for the newbie question but what exactly do you grind on the crankshaft and does it somehow increase performance (e.g. hp) or is it just to have a smoother running machine?
Thanks
Ramon

[Bigdog]

Ramon - the surfaces where the crankshaft rests in the bearings will wear and develop grooves after years of running. Those surfaces are re-ground to a smooth surface and specific smaller diameters so that new undersized bearings can be used. Good oil pressure is dependent partially on the tightness of the fit of the internal components of the engine. As the components wear, oil pressure drops which reduces the effectiveness of the lubricating system. That reduced effectiveness will increase the rate of wear so it is a viscious cycle. Grinding the bearing surfaces of the crank and installing undersized bearings is an alternative to buying a new crankshaft and bearings which would be prohibitively expensive.