poly crank shaft

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If running an automatic you need to check the converter register. I think the '66 and back are smaller.
 
I have heard that the flange is slightly different, though not sure how. I once had a thought of using a crank out of a 1955 301 (3.125 stroke) in a later 318 block to build a 305, was told I'd have fly wheel issues. Otherwise it will drop in just fine.
 
wouldn't work to good if i couldn't hook it up to the trany. just looking for easy way out. ant body got a 340 crank for sale. i am looking. i can have the poly crank if i want to take the engine out of a 66 dodge .
 
The polly cranks I think have a completely round flange on the back, no notch cut out, but bolt pattern is the same. Just check the size of the register hole for the convertor. Also the front and rear journals are solid, where as the 340 cranks have a hole drilled in them, so it will need to be balanced properly as well.
 
My old man and grandpa stuck an old 301crank into a LA 318 years ago and it worked just fine. They did this because the class they raced in had a 305 ci limit. We still have it..it just needs freshened up. I'm pretty sure it has an 8 bolt crank though...becuz we have an 8 bolt aluminum flywheel for it.
 
The 318 poly had a forged crank. Bearing size is the same as the 340. However, the 318 poly is balanced for light duty rods, not the HD pieces found in the 340.
 
2 Darts said:
The 318 poly had a forged crank. Bearing size is the same as the 340. However, the 318 poly is balanced for light duty rods, not the HD pieces found in the 340.
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Most of the posts on this page are correct. I use the 318 poly cranks when I can get them.

You should ALWAYS balance. Never ASSume on that. The flange is the same for flywheels. Can't say anything on the TQ register. If it is different, any local converter shop can do a replacement converter for cheap.
 
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