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Discussion Starter #1
What is the difference between two similar sbc cranks, both with a 2.10 journal, 3.75 stroke, the only difference is that one is for a 6.0 rod and the other is for a 5.7 rod? Does it have to do with the balance or something else?
 

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I think it has to do with the size/shape of the counterweights. Picture when a piston is at bdc the 5.7 rods pin is closer to the counterweight.
By the way, this is just my theory.
 

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Crankshafts aren't rod length specific only minimal length required to clear the counter weights. If one tried to use 5.7" rods on a 6" minimum crank, the pistons will hit/smack/drag the counter weights.
 

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AND ALSO,
oftentimes a shorter rod can be made to fit, where a longer rod is originally specified...

....BUT OFTENTIMES THE CRANK COUNTERWEIGHT IS ALSO THINNER IN THICKNESS..
or not JUST the FRONT counterweight is thinner...
so,
OFTENTIMES YOU CANNOT JUST .....
make the flat spot area of counterweight smaller to be able to clear the piston with the shorter rod...
BECAUSE IT WILL NEED tungsten heavy metal to be able to be balanced correctly...
SINCE the counterweight is less weight, because it once again is "thinner" in thickness...

dont take a shortcut like this to try and think that you are saving money only to later find out that the counterweight is not "heavy" enough and that you have to spend 200 dollars more to get it to be balanced properly...

not all cranks are like this,

..but many are..

......and you cannot "tell" with your experience just by looking at it...

AND YOU HAVE TO OBSERVE ALL of the six or eight counterweights on the crank....

not just the FRONT counterweight.

if it says to use a six inch length conn rod.. THEN DO IT....!!!!!
 

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Discussion Starter #6
Spoke with someone at Callies this morning. All I seen were cranks with a 3.75 stroke and a 6.0 rod so I asked if they had a crank for a 5.7 rod. Their answer was no, but they could turn down the counterweights for a 5.7 rod but it would most likely require a couple slugs of heavy metal.
 

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What pistons are you using? What rod are they made for? Like "builder" said you are going to be $200 or more easy in grinding and balancing the crank.
 

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Discussion Starter #8 (Edited)
Nothing set in stone. This is a new build and I'm working with a clean slate. I wanted to stay with a 5.7 rod, but a longer rod isn't out of the picture. six of one, half dozen of another....
 
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