Cutting Crank

[zachdeagle16]

Can getting your crank cut cause crankwalk in 6-bolts?

 

[blcknspo0ln]

Can getting your crank cut cause crankwalk in 6-bolts?

my educated guess would be no. and please do not cut your mitsu crank

 

[DSM90AWD]

^^ Agree. 6-bolt Cranks are Nitrided from the factory. Cutting down the journals will remove this hardened layer.

As for causing crankwalk, who knows A softer bearing journal surface would be more succeptable to wear, but the bearings themselves are WAYYY softer than even a non-Nitrided crank and the two should not come under contact in the first place if the crank is true, the right bearings are used and the journals are getting proper lubrication

 

[bryanwheat]

Although the nitrating does add extra strength to the crand, it is not 100 percent needed, on a motor that is not goint to be ran over 300 hp, it will be just fine to run cut. The cranks are forged steel cranks , so they are pretty strong without the nitrate.

 

[project_tsi]

I thought that the Nitride Hardening process protruded about .30 into the crank, so undercutting the crank was OK as long as you didn't cut it more than .20 under. Is this information incorrect?

 

[dnhieu]

i just did a bunch of research on this and the nitrate only goes .020 deep into the metal. you can send your crank off to get renitrated but good cranks are too easy to find. if i were you get a new crank its not worth the risk of snaping a crank.

just my .02 tho
david

 

[blcknspo0ln]

Although the nitrating does add extra strength to the crand, it is not 100 percent needed, on a motor that is not goint to be ran over 300 hp, it will be just fine to run cut. The cranks are forged steel cranks , so they are pretty strong without the nitrate.

why would you want/need a cut crank if you're making that kind of power

 

[Defiant]

Per Mitsubishi, the 4G63 crank is a non-serviceable item. When out of spec or damaged, it is to be replaced.
Place your bets, try your luck.

 

[TSIfreek]

There are many reputable shops building motors with cut cranks and have been for many years. The most I would go is .010 on both the mains and the rods. If your making 600HP+ a new crank would be the best choise but other than that a properly cut and polished crank will be just fine. And no cutting a crank will not give and engine more possibility for crankwalk.

 

[treebonker]

i just did a bunch of research on this and the nitrate only goes .020 deep into the metal.
david

I havent come across anything thats actually valid, I would love to hear where this .03 .02 depth came from. Even guys at Hyundai which I would imagine have a similar if not the same nitriding process didnt want to/could not give out such info(FWIW hyundai cranks are nitrided aswell). Will it have the same hardness after grinding .01? common sense tell me no. I would just follow the service manual that states the cranks are not serviceable, whether or not it makes XXXHP. It isnt a hard to find item.

- treebonker

 

[bryanwheat]

why would you want/need a cut crank if you're making that kind of power

Well the only reason for cutting a crank is if the journals are bad, if you don't believe that it can be done, go talk to slowboy, they cut them. You can cut the .010 all day long and not have a problem

 

[nanokpsi]

They can be cut, but I wouldn't go more than .01 down. Buschur has the pricing listed on his page. I would send mine to him before I has a local place do it though.

 

[luvmygst]

I just had a reman- crank snap in two. I spun a bearing about 3-moths ago I needed a quick fix so I bought a crank kit, it was cut .25, or 10 thousandths on the rods and mains. It lasted about 8k miles. I dont know if it was because it was turned or not but something to think about. Everyone says cranks are easy to find. I had a hard time finding a good crank that had not been worked. This may not even apply im not sure if the 7-bolt is nitrided but mitsu. says the same thing, non servicable.

 

[nanokpsi]

I just had a reman- crank snap in two. I spun a bearing about 3-moths ago I needed a quick fix so I bought a crank kit, it was cut .25, or 10 thousandths on the rods and mains

maybe I'm just crazy, but how is .25 = .010? I could very well be taking this out of context though.

 

[zachdeagle16]

I purchesd a remand crank from slowboy, before doing so I had a long conversation with them. They Cut the main and rod journals .010 they also said that they have several cars making over 500 hp on them. Many of there long blocks and short blocks also come with cut cranks.

 

[Defiant]

maybe I'm just crazy, but how is .25 = .010? I could very well be taking this out of context though.

0.25 millimeter = 0.009 842 52 inch

 

[luvmygst]

I went and looked and I was wrong. The crank that broke was cut .25mm on the rods and .50mm on the mains. Mabey that is why it broke??( mabey I should have put mm on the first post.. Sorry)

 

[DSM90AWD]

Just my opinion, but if I was spending a few thousand on an engine why would you want to throw in a weakened crankshaft that even Mitsu does not recommend turning?

Excerpt from Magnus Motorsports whom IMO is the most knowledgable/innovative DSM engine builder on the planet:

Crankshafts - We always use perfect crankshafts, never ground undersized. Grinding a crank takes the factory nitriding out of the crank, this will weaken it. We only start with a standard size crankshaft, not a remanufactured unit that you can get anywhere for 200 bucks

Bottom line is why spend extra money and risk further engine damage on a cut a crank?

 

[luvmygst]

It is my understanding that the nitride coating only pourpose is to harden the bearing surface. It doesent really strenghten the crank. I may be incorrect and if I am please correct me o wise one. Doesn't Sloboy use cut cranks in their motors? I'm just curious.

 

[bryanwheat]

It is my understanding that the nitride coating only pourpose is to harden the bearing surface. It doesent really strenghten the crank. I may be incorrect and if I am please correct me o wise one. Doesn't Sloboy use cut cranks in their motors? I'm just curious.

You are 100 percent correct the nitrate only hardens the bearing surface, not the over strength of the journal, so cutting one .010 is not going to be a big deal at all, like i said i have done it before with no ill effects. It is really just a prefrence thing though, like i said they are a forged steel crank from the factory.

 

[treebonker]

It is my understanding that the nitride coating only pourpose is to harden the bearing surface. It doesent really strenghten the crank. I may be incorrect and if I am please correct me o wise one. Doesn't Sloboy use cut cranks in their motors? I'm just curious.

Yes, it's sole purpose is to resist wear, which the grinding will take away.

What type of nitriding process mitsubishi uses for how long and to what depth it effectively penetrates, nobody knows.

We are left with the service manual stating it's a non-serviceable part and we have the I/he/she/they have been doing it for years without any problems. Pick one.

- treebonker

 

[Defiant]

I think the question has been sufficiently answered (and guessed-at).