Dwight - with all due respect, there is only one method and that's to look at what it says in the NHRA classification guide, see that it says 7.65 @ 411 and to abide by it. No need for a calculator.
Now if anyone feels the 7.65 was put in the guide by error, then take it up with NHRA and hash it out. In the mean time, this combo should be raced at 7.65 with a HP rating of 411.
Quote:
Originally Posted by Dwight Southerland
According to the class guide, the P/W factor is 7.65. That is SS/D.
The confusion may have started because of the two different methods to determine class when replacement heads are given a different power rating.
Method 1: If you say that the calculation is based on shipping weight, then the classification for the aluminum head is calculated by the different power rating divided into the shipping weight and results in a new P/W factor not listed in the Class Guide. (65 Corvette 396 shipping weight is 3022 lb / 411 = 7.35 or SS/C. The car can run in SS/B, C or D. This may be how Jimmy is getting the car classified in SS/B.)
Method 2: If you say the calculation is based on the P/W factor listed in the Class Guide, then the classifications stay the same as indicated in the Class Guide, but the weight changes. (65 Corvette 396 P/W factor is 7.65 SS/D so it runs SS/C, D or E. The minimum weights for the classes is based on the power factor with aluminum heads aluminum heads.).
I have had this ongoing conversation with people from NHRA tech for several years and the opinion/answer changes. The last statement from them was number 2.
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