Running a cut crank

[RadDsm]

I'm in a predicament right now. I've got 3 cranks, and they all need a bit of machine work, one only needs to be cut .010.

Has anyone ran a cut crank? I'm looking to make 450whp on this motor, and I don't want the crank to be the weak part or failing after the last 13 months of saving to build the car.

If someone could give me some insight about it, I'd greatly appreciate it because I'm tired of buying cranks, and this is the only thing holding me back from getting everything put back together.

 

[Redwidow]

You are not going to break the crank. Even if it is cut with oversized bearings, it will be just fine. My buddy is using a cut crank in his 491 hp 2g with no problems. you will be fine.
-Andy

 

[dsm-onster]

http://www.dsmtuners.com/forums/newbie-forum/324141-6-bolt-crank.html

Guys outputting ALOT more than your goal have run cut cranks just fine. Comes down to quality of the machine work. Even the service manual says two different things only a page away. So there's no real solid word from mitsu that you cannot cut the crank. Further, nitriding is a surface treatment so it only hardens the .03" depth of the journal alone. Cutting into it wont compromise the overal strength of the crank. And if you do just .01" under like I did, you still will have plenty of nitriding left on the journal. I've been runing mine like this with the holset and substantial logged flow for a while now.


ALWAYS ALWAYS ALWAYS magnaflux a crank that needs to be cut. I mag cranks that are in good shape even. If it has to be cut to be used there could have been enough heat developed to cause microfractures. Guys who've split cut cranks probably never magged the crank. Mag it before the polish. The polish work can sometimes hide the fractures.

 

[BIGBLAZE79]

I spun the number 2 rod bearing at 107K miles with no crank walk. Had the crank rod and main journals ground, nitrided then micro polished. My bottom end has held up just fine.

 

[dsm-onster]

Meh, so did I. Brand new block and fresh uncut crank. I spun the number 2 rod as well actually . . . Doesn't mean full .03" of nitriding would have helped you. Like I said several have pushed the cut crank to 700+ whp. . . Examples referenced in my link. Even the factory recomends cutting the crank if there's scores. I linked proof. There's too many variables in your situation to prove it was the fact it was cut alone that caused the issue. If everything was done right and you have proof the crank measured within spec (at certain points), then machining was done wrong. Like I said you need a proven machinist who knows what they are doing.

. . . . EDITh fvck Im a retard. . .

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I see what you mean. You're agreeing that a cut crank works fine. . . I fail.

 

[cyclonekid77]

I had my crank cut when I had my engine built and I never had any trouble with it at all.

 

[sschambers]

Just to add to the list, before I sold her I ran a cut crank in my motor. Held up prefectly fine without a single problem. Was only around 260hp but I know it would've held much, much higher than that.