318/340 cranks ???

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limelite70

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will a 1970 318 steel crank work in a 72 340 block ??

im thinking the stroke and bearing size are different.
 
put a (good running ) 340 in the swinger last weekend.
runs strong but has a wobble .???
steel crank has many markings and holes plugged etc.
so i dont know what i got.
tried 70 and 72 balancer.
still no good.
looks like it has to come out.
 
Just as they said, it will work but you have to rebalance the assembly. Pistons are different weights.
 
They do interchange, however, the #1 & 2 and #7&8 journels (318) do not have the 5/8th hole drilled thru it to compensate for additional weight of the 340 rod.
This in theory makes the 318 crank stronger.
It may need to be rebalanced internally, due to this.
I used to run the 318-3 truck steel cranks for the added strenghth.
 
I have a 318/3 318 steel crank in my 340.

Seems that a PO had put an aftermarket converter on it and failed to put the balance weights on it. Shook it so bad it broke the crank in the #1 main bearing. Sorta like taking a bottle of beer in your hand and shaking it as fast as you can with your elbow strapped to a table.
 
i think i will take it apart , bring the entire assembly to R.A.D in ludlow and have donald try to fix it.
thanks for the help.
 
Yep 318 crank (steel or cast) will work in the 340 block. Back in the day, it would be necessary to re-balance a 318 crank to account for the HD rods in the 340. Now, it is necessary to take into account the pistons as well.
 
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