Super Stock cranks

[Ed Wright]

A friend of mine is telling me there are new Super Stock crankshaft specs on NHRA's website. I may be blind, but I can't find anything. Anybody know what he is talking about? I can't reach him right now.

Thanks, Ed

[Bub Whitaker]

NHRA clarifies crankshaft rules in Super Stock

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4/18/2007


The Tech Department has issued a list of frequently asked questions and answers on the subject of crankshaft modifications in Super Stock and Super Stock GT. As with any category, engine builders in Super Stock are constantly looking at smaller and smaller details in their quest for horsepower, necessitating periodic clarifications or interpretations of the text contained in the NHRA Rulebook. Input from NHRA Technical Inspectors, engine builders, competitors and manufacturers was used to determine the correct and current answers to these frequently asked questions, and to better clarify NHRA's position on what is and what is not acceptable. The following information pertains to Super Stock (Section 6A) and Super Stock GT (Section 6B) ONLY. For questions and answers on other classes or categories, consult the 2007 NHRA Rulebook or contact NHRA Technical Services headquarters.



1. Can the mains be gun drilled? YES



2. Can the rod journals be gun drilled? YES



3. Can the counterweight be turned down in radius for balancing purposes? YES



4. Can the counterweight be narrowed? NO



5. Can the counterweights be pendulum cut to remove weight? NO



6. Can the leading edge or trailing edge of the counterweight be radiused or bull nosed? YES, because there are OEM cranks that are made in this configuration. BUT, knife edging the leading or trailing edge of a counterweight is prohibited.



7. Can the rod journals and main journals be any size? YES



8. Can a billet crank be used? NO



9. Can a forged crank be polished? NO. The rules state that crankshafts must retain OEM configuration. If a polished crank and a billet crank were set side by side you could not tell the difference by just visual inspection.



10. Can additional oil holes to the main and/or rod journals be added? YES



11. Can additional weight, such as heavy mallory, be installed in the counterweights? YES, BUT only in amounts relative to a “normal balance job”. A normal balance job on a Super Stock engine such as a SBC 350 may involve turning down the counterweights to balance up with the “lighter than stock” piston/pin/rod assembly. A normal balance job on a Super Stock engine such as a SBC 400 that is internally balanced may involve installation of mallory to offset the piston/pin/rod assembly. If mallory metal is used, it may mean too much was taken off the crank. So a small amount of mallory is ok for “normal balancing purposes”. Otherwise, mallory metal means the counterweights were turned too much, beyond that necessary for a “normal balance job”, and would be grounds for disqualification.



12. Is there a method to find out if a particular mfg crank is an accepted part? Contact Technical Services in Glendora. If you have a crankshaft that you would like to have accepted, send a link, catalog, or other information to Jim Skelly in Glendora.


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[Ed Wright]

Thanks!!

Ed