2.4 OEM crank is it okay to turn it .10

[garputo2]

I have posed pics on my other post. I was told from english racing do not turn the 2.4 OEM crank its not a good thing to do I think the logical thing to do like jusmx said turn the crank .10 throw new bearings on and go at it. I was thinking of turning them all .10 throw new acls on and main bearings also going thru everything else to ensure there was no other damage from the pos oil squirter. I plan to be running around 6-800 hp to the wheels right now I am at 500 so therefore I dont need a crank to break or other issues. This is my baby and I dont think I can come to terms to sell it just cant do it. But I am running low on funds I own 4 other dsms that are going to be sold.

http://i291.photobucket.com/albums/ll305/garputo/crankissue-1.jpg

 

[ALP584]

While my power level is no where near 500 hp like yours, I have a 6 bolt 4g64 2.4L that has the mains and rods both turned ten under with ACL aluminum bearings. 10,000 miles later no problem, I think the the oil clearance is going to be important rather than whether you turned it or not. My oil clearance is set to the factory clearance of a 2.0L motor.

 

[Strm Trpr]

No, it's definitely not ok to turn any crankshaft journals down .10".

Although frowned upon, but many do it anyway, it is ok to turn the crankshaft down .010".

 

[1fastlaser]

Its always hear say this and that. My personal opinion is no. I had a 2.4 and the machine shop insisted on cutting it, I said ok...5k later the crank broke. It might not of been that but ever since it makes me scared.

I got lucky with the brand new piston and rods I had in there. Got a fresh crank micropolished balanced and got it all back together, and have not had one issue with 700+ hp at the crank.

 

[huafist]

I've never had a problem doing it, just make sure whomever does it maintains the fillet radius on the journals. IMHO inattention to this detail is is why cut cranks fail.

 

[dsm-onster]

Cranks break from microfractures caused from heat from the previous bearing contact. They do not break from having less nitriding surface. Nitriding surface treatment penetrates only 0.03" deep. It cannot remotely increase the rigidity of the crank. And if it did contribute to a harder crank significantly, it only causes it to be more brittle, NOT what you want for a crank. That is why it is good that it is only 0.03" deep.

Further, going .01" deep means what about 0.03" deep nitriding? Simple math . You don't *need* .03" deep nitriding. It just fortunately penetrates that deep. If you cut into a nitrided journal at any depth, you still would need a turn down, no matter the depth of the nitriding.

If your crank requires turning, then 1) its the machine shop's responsibility to properly magnaflux the crank To find microfractures. As well, 2) a crank can be improperly cut, as mentioned above. A good shop can turn your bad crank into a good crank for under $130. A shop that misses the target in one of these two areas can further exasorbate the situation. So ask them how they find the possible heat fractures, at least. If they cut it wrong, then you can see that with a measuring tool, if you take the time to measure properly. . . Ideally, you should just go to a shop who has a good reputation for cutting cranks. My machine shop does not cut cranks in house, but ships them to a top rated crank cutter, who has the best reputation in his sprawling area.

My turned 0.010" under crank has survived 52lb/min pulls. and 128mph trapspeeds with full weight T/E/Ls. Been in several setups running strong.

And in anticipation of likely future responses. . . The Factory Repair manual on one page says not to turn the crank because of the surface treatment, But literally turn the page over and it says, when scored, undercut to the proper size.