[Bill Harris]

You don't have a choice on shipping weight in the regular S/S classes. The NHRA classification guides tell you what the shipping weight is for a particular body style/engine combination, and that's that. You can run the "natural" class, or move up one class, or down one class, by juggling weight. That's it. If the car's natural class is, for example, SS/E, then you can run it in SS/D, SS/E or SS/F. Even if you could take out enough weight to get it into the SS/C territory, it wouldn't be legal.

So, on a '71 Mustang Fastback with a 351/280/305 shipping weight is 3249 lbs directly from the classification guide. That's a HP/weight of 10.65 (3249/305 = 10.65). That puts it in SS/I which is 10.00 to 10.99 lbs/hp. If the car was a Mach I the shipping weight for the 351/280/305 engine is 3296 straight from the classification guide. That is HP/weight of 10.84 (3296/305 = 10.84) which puts it in..... you guessed it.... SS/I. So it doesn't matter if you claim the car as a fastback or a Mach I, you'r still a natural SS/I.

So now you can run SS/I, or go up one class and run SS/J, or down one class and run SS/H. That's it.

At this point, the shipping weight of the car is totally irrelevant. All you need to know is that the shipping weight ALLOWS you to run SS/H, SS/I or SS/J. Now you can calculate the minimum weight for the car in each class. The shipping weight doesn't come into play anymore. The only thing that is important now is the factored HP and the class. For SS/H, the minimum HP/weight is 9.50. So at an NHRA factored HP of 305, the car has to weigh 9.50 x 305 = 2897.5 lbs..... but that's not all.... You ALWAYS have to add 170 lbs for the driver, so the race weight for SS/H will be 2897.5 + 170 = 3067.5 lbs. Using the same procedure, the minimum race weights (with you in the car) are:

SS/H: (9.50 x 305) + 170 = 3067.5 lbs
SS/I : (10.00 x 305) + 170 = 3220 lbs
SS/J: (11.00 x 305) + 170 = 3525 lbs

Those are the minimum weights that you have to weigh when you cross the scales after a run with you in the car. You can be heavier of course. However, you may get an argument from tech if you are claiming SS/H and you go across the scales at 3300 lbs (which is SS/I territory). They might not say anything.. and they might give you ****... hard to tell.

Now, just because a car is ALLOWED to run a particular class doesn't mean that it CAN. If you want to run at the bottom (lightest) of SS/H with the '71 you have to get the car down to 3068 lbs with you in it in a manner that is legal for S/S. Good luck with that.

Stock classes and weights are calculated exactly the same way but using the stock HP factors.

My '71 Mach I with a 429/375/360 runs D/SA at a minimum race weight of 3590 lbs.... (9.50 x 360) +170 = 3590. I could run C/SA at (9.0 x 360) + 170 = 3410 lbs, but it would be really hard to get 180 lbs out of my car legally. Anyway, it wouldn't hook if I could.

Hope that helps.