I am building a 470 stroker in a 400 low deck block for my 1969 Road Runner. I have a 440 forged crank that has been machined for this application but was never nitrited surface hardened. Is this a must do on a forged crank?
Hmmm. You’ve got me wondering what kind of machining was done? Hopefully, the block has been align-bored to 440 main size. To cut the crank to 383/400 size weakens it significantly and is not the hot ticket. At any rate, any time a crank is cut, and will see serious performance use, surface hardening is a good idea, I always insist on it. As far as must-do? If the engine will see only mundane, cruise-type use, it should be OK without.