S.H.P. CRANKS

[NANCY CHARLES]

can some one tell me what the casting # is for the 327/340 S.H.P cranks ? there are # 2680 forged steel being sold as special high perfomance & fuel inj cranks without the snouts drilled & tapped . HOW CAN ONE TELL ? thanks all

[Joe L.]

Re: S.H.P. CRANKS

Nancy----

Generally, the 62-65 SHP crankshafts were denoted with the "2680" forging number. The crankshafts for non-SHP (i.e. 250 and 300 hp for Corvettes) were denoted by the forging number "3782680". I don't know why there would exist "2680" forgings which were not drilled and tapped for the balancer bolt. However, lots of things can happen in SERVICE. It may be that some of the "2680" forgings were used to make-up non-SHP finished crankshafts.

As far as the basic forgings go, they're pretty much the same for both crankshafts. All 327 crankshafts through 1967 were of forged steel construction. Different alloys may have been used for the "2680" versus the "3782680". If so, I'm quite confident that the "2680" forgings that you're referring to are made from the "upgraded" alloy, if, indeed, there was any difference in alloys. It's also possible that the balance weight configuration was slightly different due the differences in weights between the SHP and non-SHP pistons.

The other differences between the SHP and non-SHP finished cranks related to the balancer snout tapping and the surface treatment of the journals. Non-SHP cranks during the 62-65 period didn't have the balancer bolt and didn't have hardened ("nitrided") crankshaft journals. SHP cranks had the snout tapping and generally had the hardened journals.

So, to determine whether the cranks in question are truly SHP pieces, you would need to evaluate the balance weight configuration (hard to do unless you have particular experience in this area), the snout tappings (which, apparently, are not present), and whether the journals are hardened or not.

The hardened journals and the snout tappings can be added to the crankshafts if they are not currently so-endowed. The balancer weight configuration is, basically, moot since if you use a SERVICE crankshaft you should always have the engine custom-balanced, anyway.

So, the bottom line is that even if these crankshafts are not fully configured as the SHP piece, they can be readily "transformed" into the SHP piece if one so desires.