knife edged crank

[overboostmotorsports]

anyone have pics of a 2.2 crank they havbe knife edged ? i plan on doing mine but want a reference point to make sure it was done right.

Norm

[RoadWarrior222]

General info, non 2.2 specific...
http://www.turbomagazine.com/tech/0610turp_castillo_crankshaft_service/photo_02.html

[A.J.]

Wouldn't this be a moot point if you have a crankcase evac set-up pulling a vacuum?

A.J.

[turbovanman²]

Wouldn't this be a moot point if you have a crankcase evac set-up pulling a vacuum?

A.J.

No, because the oil is still being whipped and this also lightens the crank, :thumb:

[RoadWarrior222]

IF you're not bothered about lightening it too much, you can just knock the edges off it a bit, easier to balance up again. I'm just gonna do that to my spare 3.0, and add a scraper.

[zin]

Just a side note, if you're doing it yourself, the trailing edge is the most important aerodynamically speaking, and definitely have the rotating assembly re-balanced!

Mike

[RoadWarrior222]

Good point, leading edge really only needs to be rounded, back edge feathered as thin as possible, and keep it symmetrical or it will create a sideload thrust against your bearings.

[Directconnection]

All of the top end cranks I see at work have the leading edge radiused, and the trailing edge knife edged. Think of an airplane wing :thumb:

The circle jerks really go nuts with weightloss in the reciprocating system. Crower Maxi-lite cranks are kick arse, too. Sacalloped, radiused/knife edged, rod journals drilled, etc.... even the flange is machined for lightness.. (profiled)

Side note... lightened up too much is a bad thing. We turn down the counterweights on a few... and on one toyota 22re the crank had almost zero counterweight and it ended up cracking. The counterweights in an inline engine are also used for dampening.