318 crank in a 340? Will it work?

[khenrichs70]

OK so a 318 and a 340 share the same stroke but will the cranks interchange? I really can't think of why not inless the 318's had a weaker crank shaft? One guy said yes and the 318 steel crank is lighter than a 340 crank. I'm really am not sure. Also what 318's got steel cranks?
Thanks Kyle

 

[SGBARRACUDA]

OK so a 318 and a 340 share the same stroke but will the cranks interchange? I really can't think of why not inless the 318's had a weaker crank shaft? One guy said yes and the 318 steel crank is lighter than a 340 crank. I'm really am not sure. Also what 318's got steel cranks?
Thanks Kyle

You can use the 318 crank but the rotating assem. will need balanced.

 

[grimreaper]

If you don't already have a crank look for a 318 truck crank. They were forged and hardened. We used to find them regularly in military vehicles. P/N2843885

 

[2 Darts]

The short answer is yes, if you re-balance for the 340 rod/piston assembly.

The old poly 318 (61-66 US/67 CDN) crank is forged steel as is the 64-67 273. All are 3.312 stroke cranks balanced for light duty rods.

The 340 (and 360) used heavy duty rods. In the case of the 340 crank, this is where the balance issue comes in.

 

[rumblefish360]

As a side note, the back of the crank may or may not be drilled for a 4spd use. If such is the case that you have a 4spd manual, do check this before you go any further.

 

[khenrichs70]

I though this would work and the fact that it is lighter is even better. I plan on using afermarket rod and light pistons.
Thanks for all the imput Kyle

 

[SGBARRACUDA]

As a side note, the back of the crank may or may not be drilled for a 4spd use. If such is the case that you have a 4spd manual, do check this before you go any further.

Also i have found out in the past that the back of the cranks where the converter hub goes is a different size from 65 ish back and later.