has anyone had there crank knife edged on a 4x4 cosworth????if so what do u think ????????

 

there seems to be more and more norther monkeys poping up on the board, as for the knife edged crank i dont have a clue

 

its not something you can really notice tbh
it just gives less resistance as the crank hits the oil in the sump . but you probably allready new that

 

i done mine on my 2wd saff

I did it as a matter of course when i built the engine!!!!!!!

I think every little helps

 

cheers folks

 

oi rudey
read my thread for you
i had knife edging done on my shaff , but i think they have to be carefull not to take too much off or it becomes weak

 

It is much more common on NA engines than on turbo ones.

Personally I"d worry more about having the rotating assembly dynamically balanced than I would knife-edging the crank....but as always, YMMV

 

the crank arms (or lobes) are machined on the edges to make the crank cut through the oil better. Also less weight

I think thats correct

Well i know what is done and whats it done to, hard to explain, but im pretty sure thats the reason aswell

 

dont bother on a cossie, for one simple reason

ave a look where the oil is on a cossie and where the crap swings

 

Time to show these pictures again for the "it makes the crank cut through the oil faster" believers Gareth


(my own work )



I beleive it's done so you have less recipricating (SP?) mass i.e. it makes it rev faster

 

Fit a crank scraper if you're worried about knife edging the crank, that's assuming anyone has made one for a Cossie?

 

Really not the best idea IMO to be removing lots of meat from the crank.. esp when it is taking such a large ammount of power all in one go...
Knife edging is done mainly on N/A engine to help them rev harder... this isnt needed or applicable on a turbo charged engine and is therefore of no use..

 

Useful on high revving motors where the crank is buried in the sump.
Cant see the point on a cossie though.

It will NOT make the crank more likely to fail though, less material doesnt always equal weaker, and in fact you only have to look at smoothing metal off like con rods (ie really heavy polishing) and you can see that often less metal is in fact stronger.

 

I saw an experiment in a magazine back in the late 80s early 90s and they put a perspex window in a sump so you could seee what was going on and the crank acted like an egg whisk, with alot of oil trapped in the rotating assembly like when you whisk an egg.
Knife edging will make it more aerodynamic so in theory is should cut through the air/oil/blowby gasses or whatever else is there more effectively.

 

you can only make a dramatic improvement in terms of not churning up the oil too much if it does it in the first place though of course!