Here is a photo of a cast crank. See any differences . . . anyone?

 

please let us know what you think the best choice is for a performance 100mm crank.

 

Hmmm, I can't see the other picture right now, but is that a Mitsu crank also? I had thought all Mitsu cranks were forged, being that the difference was that only some of the 4G63 cranks were nitrided.

 

The other crank is not a Mitsu crank.

Take a look at these photos (look at the arrows) and someone tell me what difference they see.

 

the two cranks both have lines down the center. the busted cranks line is flatter than the other one.

what would your choice be for a performance 100mm crank?

 

That wide, flat line is a forging line. Cast cranks have a narrow, raised casting line.

This is how one tells the difference between a cast and forged crank.


Many people have used a factory 100mm crank without issues. Broken cranks are typically the result of something other than the crank spontaneously failing. If one wanted to throw money at it, I wouldn't buy anything less than a billet crank.

 

Makes sense.....good eye Ted B

 

I stand corrected.

I noticed that (flatline) but I could have sworn he had told me it was an older cast crank. Anyway, I know as many people that have busted cranks at the #4 main as have been hard on them with no failures. That particular crank was never spun higher than 7500 rpm, no nitrous, just ran on a somewhat tired Red and meth. It was also a long rod motor so running 7500 should have been cake. I suppose it could have had some microfracturing or other unseen problems before it was installed, but I am dubious about it being tuning related. Jake M and Lucas E both busted cranks in motors season before last.

 

There are several things that can contribute to an untimely demise for a crank that don't have anything to do with tune, rod length, etc. If there was a problem with straightness or clearances, a flaw in the metal (have it magnafluxed beforehand), an imbalance, or very possibly, excessive harmonic issues as a result of high torque loads and insufficient dampening (due to a lightweight crank pulley).

I'm not a big advocate of a 100mm stroke crank in these motors, but if I were going to do this and take it out and beat on it, I'd definitely consider investing in a billet crank. If it prevents so much as one such instance of breakage, it's paid for itself.

 

thanks for letting all of us hear the voice of experience Ted B. How long have you been slinging Absynthe. I drank half a bottle of that mixed with some bolinger champange one New Years Eve. I didn't come out of that haze until February!!!

 

I dont have a budget for a billet crank so its either 4G64 or eagle. Ive decided to go for the eagle in any case. Will look into the balancing of it for peice of mind.

 

Read the first few words from my original post.. "Take this for what it's worth" remember that?

Also, seeing as how your friend had/has an Eagle crank, that's not FIRST hand, that would be SECOND hand... Which makes your post about as useful as mine. However I aknowledged this is second hand info.

All I'm saying is that there have been issues with them, and I suggest the OP get it balanced before basing a build around it. Or get a billet or forged K1 crank, and even then I would suggest getting it balanced. It's just a good idea no matter how good the quality is to start with.

Also, aren't there two versions of the 4g64 crank? One forged? One cast?

 

 

do you take it to a fab for balancing? or it something ya do yourself?

 

Dynamic crank balancing is performed by better engine shops, and is a very wise proposition.

As for 4G64 cranks, I have no idea if there are two versions (cast and forged), but if they are, it would easy enough to tell them apart as I illustrated above.