Crank Shaft

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J

jam4ever

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I was wondering if there ir any modification to a LA 318 Block if I was to use the crank out of a poly block? Are there any advantages and/or disadvantages.

Thanks for your time-
 
I am not sure but I don't think you can use a crank from a poly engine in a LA engine! Two different animals completely I think! Maybe someone with expertise will tell us for sure but I would guess that it will not interchange!
 
I have a '65 poly 318 crank in my 340 in my drag car, they bolt right in. If you use a '65 or '66 crank the convertor register is the same as the LA's but somewere in '64 and down the convertor register is smaller so it would have to be machined out to fit a later model convertor. You will have to balance your motor, the poly has different piston/rod weights than the LA. I have been picking these old polys up for years when someone wants to throw them out because they have forged cranks.


Chuck
 
It's a '66 crank. I had heard something about the rods being lighter that La Rods. Any truth?

Jeremy
 
Yes the poly rods are lighter that is why you need to rebalance the LA if you want it to be right. But it will physically both right in if you didn't want to balance it.

Chuck
 
You could but they are full floating and most 318's are pressed pin. Plus the poly pistons are a different weight also. For a basically stock motor there would be no advantage to installing a forged crank. I have never seen a 318 break a cast crank. The reason I installed the poly crank in my 340 was it was a cast crank 340 that had a two spun rod bearings and the crank was already at .020, if I didn't already have the poly crank I would have considered using a cast 318 crank.

Chuck
 
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