cutting the crankshaft?

[steve]

Pinknuggit, I wish people would stop pointing pointing at my response to post #1 as in some way related to Cesar's thread hijack.

I think I gave a perfectly good response to the question "what does it mean to cut a crankshaft" I tossed in the issue about the cranks being nitrated to give Race94 something else to think about and possibly research but as I pointed out later I couldn't remember, with the level of confidence I prefer, the specific details so I left it open.

 

[pinknuggit]

no, your post was not wrong in anyway, it was just that your post was pointed to ceasar as an answer to his question when it was clearly not. Ceasar asked if he needed a new crank, and that one guy pointed to your post as an answer, when it really didn't have anything to do with ceasar's question in the first place.

I think it's funny how people give advice to "chunk" the crank if it needs to be turned.

 

[bigjangin]

This thred is so misleading it's not even funny. You do not need to chunk a crank if it needs to be turned (a.k.a, knife edged, cut, whatever you want to call it). You can run it as long as you have oversized bearings. We turned a crank .020" over for a guy here at work who also has a dsm. He put 322whp down on a 20G and has been running the same setup for over a year now.

Saying that someone needs to find a new crank because their needs to be turned is BAD ADVICE. Yeah sure, the stock ones are nitrided, but just because you take that off doesn't mean the crank is junk. Odds are, very few people on here are running enough power to have a need for nitrided journals. There Are plenty of machine shops around the country that can Re-Nitride the journals.
A crank that has been turned has a higher chance of breaking in half vs. one that hasn't, but that chance isn't enough to even make a difference unless you're running ungodly amounts of power. Hell, you have more of a chance of bending a connecting rod than breaking a crankshaft which has been turned.


And i don't know about everyone else, but i'm on ceasar's side. I could not see a clear answer to his question.



He asked: "I should find another?? 6 bolt.
"

Post #3 answered :"Usually that means putting the crank in a lathe and turning the main and rod journals to make them round and smooth again. Your cutting metal off the crank.

Some DSM cranks have a nitrated surface hardening treatment and turning them will remove the hardening.



Post #5 answered :"
Some? Every six bolt does and that's all that matters. If you're rebuilding 7 bolts, well uh good luck



Now is it just me, or do i NOT find a SPECIFIC ANSWER in the replies?!?!?! He asked a question which needed a YES/NO answer. I don't see ANY relevance to his question in those replies. Simply implying that "a turned crank weakens the surface" is Not a very good answer to "should i get another one?" Remember, people on here can Not read minds.
People should also refrain from posting unless they have personal experience with the topic matter. It's obvious that the people who say a turned crank is bad do not have experience with running a turned crank in their motor.

If it were me, I would not run a turned crank in my own personal car. If the car will never see modifications and will never be launched, Im sure it will be fine. But in a dsm with decent mods that will be raced, I wouldnt run a turned crank unless it was renitrated. Oh and turning a crank and knife edging are totally different things, Im sure it was a simple mistake on your part, but if you really dont know the difference you shouldnt be giving advice on this subject.

http://www.teamnabr.com/ubbpub/ultimatebb.php?ubb=get_topic;f=10;t=000542

Just a recent example.

 

[Cesar]

Thanks for the link, but that guy was runnning a solid pulley...

http://www.dsmtuners.com/forums/showthread.php?p=1106385#post1106385

doesn't necessarily mean it was the cut crank at fault.

I'm not disregarding that post, I do take it into consideration; nonetheless, I'm still skeptical. Remember though, I am looking for a standard crank.

 

[Cesar]

after reading the entire thread from the nabr link, I noticed incidents with uncut cranks also...

 

[pinknuggit]

well then educate me: what's the exact definition of "knife edging", and what's the exact definition of "turning" ?

It's easy to say "i won't ever run a turned crank in my car" without running one. I've got plenty of launches and engine use on my old crank which was turned .010". We turned a crank .020" over for a friend, and he has many launches and has ran his engine hard with a 20G for over a year. I've never seen anyone break a 4g63 crank that's been turned. I've seen stock cranks break in half, though.

 

[steve]

"turning" the crank and "knife edging" the crank means the same thing, which is resurfacing the journals.

There goes any credibility you might have on the subject. ( I see you edited your original post. Good idea!)

Knife Edging a crankshaft is shaping the counterweights to reduce the turbulence caused as the rotate through the oil vapor in the crankcase (not oil in the pan). Usually that means the leading edge is ground to a "knife edge" but other more aerodynamic shapes have been used.

Here's an example from ffwdconnection where they knife edge the trailing edge:

You must be logged in to view this image or video.

Steve

 

[pinknuggit]

yeah, it didn't hit me until i re-read what i wrote.

 

[NDgsx]

There is no reason to bother turning a crank. I can get good used 2.0 and 2.4 cranks for $50-150. These things are not made of gold, they are not rare.
There isn't as much worry about fillet radius being correct and no worries about the surface hardness just using a different crank. Why bother risking it and waste time when you can get a sure thing for less?
There a lot of machine shops that nitride cranks? Why don't you call around the country then and tell us what precentage of machine shops actually do. Specialty crankshaft shops nitride cranks. Normally even performance machine shops aren't equiped for nitriding.

 

[Cesar]

There is no reason to bother turning a crank. I can get good used 2.0 and 2.4 cranks for $50-150. These things are not made of gold, they are not rare.
There isn't as much worry about fillet radius being correct and no worries about the surface hardness just using a different crank. Why bother risking it and waste time when you can get a sure thing for less?
There a lot of machine shops that nitride cranks? Why don't you call around the country then and tell us what precentage of machine shops actually do. Specialty crankshaft shops nitride cranks. Normally even performance machine shops aren't equiped for nitriding.

I'll buy a good 2.0 crank from you for 75US. escrow okay? PM me please.

your right, alot of shops don't nitride cranks. But all you really need is one, and I got a good one 20minutes from here.