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Discussion Starter #1
Im looking at 2 bbc cranks, both are 4inch stroke. One says must use stock rod length the other says must use +.25 rod. This is not a kit ,no rods or pistons involved. What would be the difference in the two cranks to need two different rod lengths? Theres also 50 bucks price difference. What am i missing?
 

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Discussion Starter #3
So basically there is one for talldeck to use the longer rod and the other is standard deck height? The weight is listed as the same for both.
 

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just a ski boat with bark
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Im looking at 2 bbc cranks, both are 4inch stroke. One says must use stock rod length the other says must use +.25 rod. This is not a kit ,no rods or pistons involved. What would be the difference in the two cranks to need two different rod lengths? Theres also 50 bucks price difference. What am i missing?
Most likely the bobweights are different, typically a longer rod means lighter pistons. I'm just guessing and I didn't look this but a stock replacement deal probably has a bobweight of around 2500gms where the one for the +.250" rods is probably around 2300gms. The only issue is if your bobweight is heavier than the crank you bought the machine shop will have to add heavy metal to balance and that cost more.
 

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Discussion Starter #5
Thanks for the replies. The way the specs were worded just threw me off and i guess i should have thought it through the whole way. thanks
 

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Most likely the bobweights are different, typically a longer rod means lighter pistons. I'm just guessing and I didn't look this but a stock replacement deal probably has a bobweight of around 2500gms where the one for the +.250" rods is probably around 2300gms. The only issue is if your bobweight is heavier than the crank you bought the machine shop will have to add heavy metal to balance and that cost more.
Not exactly Carnalride. The REQUIREMENT for the longer rod is due to a larger diameter counter weight like Flat Screwed said. The reason for the larger counter weight is not due to a lighter or heavier piston, its so you can internally balance the crank without mallory metal. It also allows the manufacture to remove the big ass pork chop on the flywheel flange, that really act like nothing more than an external weight. If you don't run .250 longer rods, the piston will crash into the counterweights.



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