Lightened, knife edged crankshaft [Merged 6-8]

[GSTdOff]

What exactly do they mean?? And how do they benefit your car??

 

[dsm1kenobe]

Read this:

http://www.bjscylinderhead.com/klcranks.php

 

[GSTdOff]

Cool,,, does that increase the redline as well?

 

[dsm1kenobe]

Originally posted by GSTdOff
Cool,,, does that increase the redline as well?

Nope, but you'll get to redline faster.

 

[Defiant]

Hm. Maybe. The line on the tach won't move, but the _real_ maximum velocity in most engines is determined either by a) valvetrain float or b) crankcase ventilation by connecting rod portion impingement.
It'll more effect how quickly you get to redline than where the redline is.

 

[turbo90gsx]

All i can say is it sounds sweet! 7 pounds off the crank, damn!

 

[GSTdOff]

Definitely sounds sweet. Would it be worth the money/time to have it done to a stock bottom end??

 

[Cheks_Talon_TSi]

Does someone knows something about Lightened knife edged crankshafts???

I really know what it means but what I want is to know more info about this ... how much extra HP's will my car get? who can make this kind of jobs? does it is recomended or will it be dangerous for my engine?? ... any kind of info will be very useful.

After making some research on this forum, I found Bj's was selling these kind of modified crankshafts but I haven't been able to enter to his web page. I guess it is www.bjscylinderheads.com ... but right now it isn't working

I am rebuilding my engine and I was thinking on buying a Lightened-knife edged crankshaft, but before that I want to know as much as I can about it...


Thanks in advance.

 

[alex99gst]

When a crankshaft has the counterweights kinfe edged, the large heavy kinda-flat pieces are chopped off and smoothed out to where an edge is "sharper" so that it in turn is able to slice through the oil with less resistance because the surface area hitting the oil head on has been reduced. It also in turn lightens the crankshaft, therefore creating less rotating mass inside the engine, both of which are positive performance wise.

The first two pictures are of a knife edged crankshaft and the last is a stock crankshaft with the counterweights still in stock form instead of chopped off.

 

[JessesTalon]

You will notice along the lines same gains as if you were putting a lightweight flywheel on...

rev quicker a guy who did this afterwords said he felt his engine was MUCH smoother running after he did it...

 

[Cheks_Talon_TSi]

Thanks for the info... seems to be a good mod for my engine... BTW, Will it be difficult to get the crankshaft correctly balanced after the knife edged job????

Any negative issue about doing this mod???

let me know

thanks

Sergio G.

 

[brute]

well the only thing i can think of in terms of negative effects would be the slight drop in torque. when you reduce rotating mass, you free up hp's but also reduce spin weight and therefore torque. so when one installs a lightened flywheel, the engine is able to rev faster, but less torque for stop launches. a reduction in rotating mass is generally for the highway-runners because, as stated before, one can rev faster. the knife edge reduction in torque may not be a bad thing if you never launch from a stop, you must make the choice yourself

 

[Defiant]

When a crankshaft has the counterweights kinfe edged, the large heavy kinda-flat pieces are chopped off and smoothed out to where an edge is "sharper" so that it in turn is able to slice through the oil with less resistance because the surface area hitting the oil head on has been reduced.

The crank on a running engine won't hit the oil. It does cut down wind resistance, and might be good for a few horsepower at high revs.

 

[Defiant]

well the only thing i can think of in terms of negative effects would be the slight drop in torque.

It won't affect torque. It does affect the amount of mass you've sped up, and therefore reduces the amount of stored inertia which saves the inept from stalling on takeoff.
Real-world benefits won't be nearly what those selling the procedure, nor those who've paid for it, think it will be.
Balancing procedures won't be affected.

 

[Cheks_Talon_TSi]

It won't affect torque. It does affect the amount of mass you've sped up, and therefore reduces the amount of stored inertia which saves the inept from stalling on takeoff.
Real-world benefits won't be nearly what those selling the procedure, nor those who've paid for it, think it will be.
Balancing procedures won't be affected.

My idea is to get some extra hp's and get a better time on the 1/4mi drag races... so will this mod help me ???WTF

Thanks in advance

SErgio G.

 

[gamingguru]

It should. Having the lightest possible rotating mass in your engine is usually the goal when building it.

 

[luvmygst]

To me it seems that if you look at (money invested/hp gained) it is not worth it on a street car. You can get close to the same results with a lightned flywheel. On a all out drag car it would probably help once you have done everything else. I would spend that money on other things for a street car. Just my .02

 

[gijoe985]

I just wrote a long post about, where do I find out about machining tricks for engine building. I then realized that knife edging is the only one I am not familiar with. I know what it is, but where can I learn how to do it effectively. I've rebuilt a bunch of engines and have done porting work, but never anything on the crank. I am assuming you do the knife edging and then you get it balanced? Please fill me in, or maybe point me to a tutorial.

 

[Supa Dexta]

I want more information from defiant on this. You say it won't hit the oil, or slap it on its down turn, but how so? The oil isn't that deep in the pan when running, since the oil is out doing it's business around the engine... So the blades would exit the oil pool and then have to reenter it again.. I would think anyways, if I'm picturing where the crank sits, and guessing how deep the oil would be anyways.. Now I know your leary of a lot of things that go on (many for good reason), but I would like to know more about this, if you have facts to post up.

 

[crimsondragon]

If your crank was actually hitting the oil, it would cause the oil to foam. Foaming in oil is air mixed with oil. If air gets pumped into the lines, kiss your seals goodbye.

 

[DougR]

Www.ffwdconnection.com butchercrank
These guys make a very nice peice,

 

[gijoe985]

I'm still curious how this effects balance? If I start hacking away at my crank (not saying I am going to or would) do I just get it balanced after I am done?

 

[fourreGsixty3]

YOU don't knife edge the crank, you send it to a specific engine shop that offers knife edging as a service, and they cut the crank, and balance it so its all good when you get it back.

 

[1992awdlaser]

I'm still curious how this effects balance? If I start hacking away at my crank (not saying I am going to or would) do I just get it balanced after I am done?

Read the link that is in post 21. These are a couple things you might be interested in reading from it.

"Lastly, each crank is then fully balanced for race operation. We're talking around .1 ounce/inches of tolerance when we balance these Butchers. To put that into perspective, "RACE" tolerance is .2 ounce/inches (the industry standard) set by Stewart-Warner Engineering. "STREET" tolerance is .5 ounce/inches. What does all this jargon mean for you? By the time we're through with playing spin doctor, you will be able to safely spin these cranks up to 15000 RPMs. Can you handle it??"

"The Butcher crank made to order! Take note that our "reconditioned" cranks are not undercut, welded on, or anything stupid. Pure virgin stuff. We wouldn't run a sub-standard crank...why would we want you to?"

 

[EagleTSIawd]

when i bought my car it came with a 1g swap and with the knife work done to it.

here are some pics of it (thought i share)

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looks like previous owner knew his stuff well

the only difference ive noticed so far is that my car revs up a bit faster then my bros. Hes got his motor fully built just no knife work done to his and we are both using the same flywheel