Best Rear Main Seal

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Originally Posted by johnneilson

Terry,
from the sounds of the caustic quench and subsequent anneal it almost sounds as if it is just to harden the surface. I do not know, however, I can tell you from cross drilling a few "C" cranks that the heat treatment is pretty consistent all the way thru the material.

I concur with your thoughts John. Several years ago I received couple of aftermarket Model-A crankshafts that apparently were not properly heat treated and failed within a short period with insert bearings. In discussions with the manufacturer this point was mentioned that the hardening process was just on the surface only based on the factory print however in my discussions with others who had drilled original cranks for pressure, their opinion was the original crankshaft hardening went much deeper than just the surface as indicated.