Forum » General Engine Building Discussion » Opinion on Knife-Edging a Crankshaft

Opinion on Knife-Edging a Crankshaft

General Engine Building Discussion

Forum Posts



Tech Articles

Talk about engine building here. New products, tricky questions or showcase your work - If it's engine building related it's welcome here.

= Resolved threads

Page 1

Knife-Edging is a process of 'sharpening' the counterweights on a crankshaft and is claimed to promote the process of cutting through the oil in the pan .

Can any experienced engine builders / machinist verify the claim ? I'm not sure if the gain outweigh the reduction in fatigue lifespan of the crank.

I found that "cutting edge" technology worth doing back in the mid-1980's (of course I was using a dry-sump, so it was only cutting air). The only change today, is that now we can run more vacuum with the dry sump, so there is less dense air to cause drag. Still, if you have the time to do it (dont's forget to have the crank re-balanced) it's probably worthwhile.

If you really want to know if it's worth it, you will need to either prepare two crankshafts and swap them for back-to-back dyno runs, or do a baseline, prep the crank and re-assembe to test the gain.

Good Luck with your project!

It also lightens the crankshaft a little, I know of several builders who knife-edge as a lightening process, rather than the other way round.

As to the benefits, some swear by it, some think it a waste of time and some figure it can't hurt if you're already reworking the crank.

Heck, some connecting rods are designed with a 'knife edge' supposedly to reduce windage losses.

Regardless, least you can do is have the crank' crack tested and checked for straightness and journal wear and, personally, that is generally where I would leave it - but I'm not a race engine builder.