The knife edge crank main purpose is to swish through the oil in the sump easier resulting in less load on the engine, the other major result is the reduced rotational mass of the crank form removing the metal to reshape it which helps the engine accelerate quicker. Some people are all for them but others don't see the benifits. I probly wouldn't go to all the way on a crank if you want it to last or if your an engine breaker but definatley getting a mild lightening and reshaping wont hurt it if your going to race or whatever

When you had your crank balanced Gary, was there much mallory metal required? I've broached the subject with my old man about knife edging a crank in his lathe, and he has concerns about balancing issues if there is too much material removed from the counterweights. I now have a stuffed crank from an A15 that threw a rod to practise on, so I'd quite like have a go.

Morgan, I was doing a sponsors day for the car club that I'm in and the track was basically a speedway track with mainly right hand corners with a couple of left handers thrown in, I knew the oil level was a little lower than I normally run it and didn't give it to much more thought, the end result I spun a big end bearing on no.4 journal. I dropped the sump and thought I could just change the big end bearings - a complete waste of time, new bearings got me around the block and that was it.

I pulled the motor out and stripped it down and took the crankshaft to Crankshaft Engineers here in Brisbane, I got the phone call from the repairer saying that the crank was bent and that the big end on the conrod was egg shaped, thankfully the crank wasn't cracked.

The crank was straightened and all journals were reground and the conrod re-sized.

Very impressed with the repair job.

Bart, When I machined this crank a few years ago I made sure I machined everything thing as true as possible with balancing in mind i.e whatever I did to one side of the crank I made sure I did to the other, even to the amount of turns that I screwed in the grub screws for plugging the oil galleries.

When I had it balanced the guy was very impressed with how little amount of metal he had to take of to balance it, basiccally it was just a small amount of linishing of each diagonal corner.

It's not a hard job to do to machine them it's very time comsuming, if you have a spare crank i'd recommend you give it a go.

I have a buggered one to practise on, as well as plenty of spares to try for good. I was just over at the old mans for Xmas breakfast, and I showed him this thread, and the picture of your in your album. No doubt he'll be able to do it. He suggested that he'd need to go quite slow, due to it not being a continuous cut. (Being all offset) And that that could cause some vibration) Although the crank isn't very long. And he's unsure whether or not it may damage the journal to try run a steady on it.Did you do much to the sides of your crank? Or just radius them? Do you have any more pictures of it?