Crankshaft knife edging.

[Preen59]

I Knife edged a 202 holden crankshaft for a friend of mine this week.. So here's some pics..

On the left is a crank i was told to use as a guide, it has been done by a performance shop in Sydney.. For the purpose of this thread i won't mention the name of it, let's just call it RAG (Rough As Guts) Engineering. On the right is the crank i have done.






As you can see, the "professionally done" crank is absolutely horrid. I can't believe someone actually charged a guy for it.

I also had to put in a steady and drill and tap the end of both cranks (easy job).

Anyways just thought i'd throw up some pics.

[gerhard]

How much does that process put the crank out of balance?

[Preen59]

How much does that process put the crank out of balance?

Shtloads. You have to re-balance the crank after you perform such an operation.

[schoona]

What's the "purpose" of "knife-edging" a crank Chris?
And then re-balancing the crank, is that a matter of spinning it on a lathe for 24 hours like turbine generators or ???

[gareth_oau]

nice looking work Preen. however, I suspect this sort of quality workmanship would typically come with a cost attached?

[Preen59]

What's the "purpose" of "knife-edging" a crank Chris?
And then re-balancing the crank, is that a matter of spinning it on a lathe for 24 hours like turbine generators or ???

It reduces the parasitic drag from the oil mist in the crank case. So basically it cuts through the mist and less oil condenses on the counterweights. All these kind of things cost horsepower. If you look at REALLY expensive race cranks, they'll be fully polished.

Balancing involves a proper electronic dynamic balancer. You either drill out the heavy side, or in some cases you drill out the light side and fill it with mallory (like copper).

I'm not a whiz on that stuff so i can't really go indepth on it but a lot of different tuners do it different ways.

nice looking work Preen. however, I suspect this sort of quality workmanship would typically come with a cost attached?

Yes. This kind of stuff isn't cheap. I did it cheap-er for my mate because he's a mate. It took about 3.5-4 hours from set up to clean up. Very painstaking work actually.

[Oneofthegreats]

Nice work as usual Preeny.

Wouldn't expect anything less.

I'll add some info to this as well.

Not only does it decrease parasitic drag from turning through the oil, oil mist & oil draining back down into the sump ie from cam journals, lobes, lifters, cyl. head drain holes & piston oil squirters etc it also shaves a substantion amount of weight of the crankshaft too. Depending on the application can be approx 1.5-2+kg's.

The decreases weight basically means the engine revs up faster & slows down faster as well.

Also when adding a sump windage tray & crank oil scraper brings the parasitic drag loss' even further.

There are other things that you can do to take advantage of the lighter crank incl. lighter flywheel/clutch combo, pistons, rods, valvetrain gear.

The best thing you can do when balancing a crank is do it as a rotating assembly eg. you balance the crank, crank pulley's/harmonic balancer, flywheel/flex plate, clutch as one!

Then you match weigh pistons, then the complete rods & you can also match weigh the rod ends eg. the big ends & mains.

If all this this is done right, the engine will run as smooth as silk even at 7+K

[Jarred]

Great work Preeny. I know who I'll be calling to get my diesel crank done

[GoLfMan]

wow they REALLY hacked into that first crank

nice work as usual, I'd love to learn how to do this, will corner you and ask you next time I see ya

[Preen59]

Just remember i don't work for free.

It's not that hard, Josh.. If i worked it out i'm sure you are capable of it too.


Thanks for adding that info, Tim. When i replied i didn't have time to go that in depth. Always good to give people more info.