Let me clarify. I guess by "better" I should have said strongest tensile strength than a 4340. Meaning it will handle stress better. The 5140 cranks do not have the other alloying metals like the 4340 which is a "moly" because it has a significant amount of Molybdenum which among strength (hardness, not tensile) it also allows for better machinability-it can be turned or machined easier than a 5140. Chromium is the primary "hard" material used in crankshafts which the higher the %, the stronger it is-albeit at the expense of making it easy to machine, etc. Molybdenum used as an alloying metal with a slightly lower % of Chromium which allows other metals to be alloyed with it to produce varying characteristics like increased scuff resistance and even MORE resistance to scaling and corrosion at higher temps. It really depends on the purpose of the motor being built as to what crank serves the best purpose. An alloyed 4340 crank is the most popular but it is not the "tuffest" crank imo-I'll put it that way-but the extras that are forged in make it worth the money. -Jabin