Super Stock GT

[Terry Cain]

OK, I know it's prob in the rule book but, at the moment I don't have one in front of me. How are GT classes figured? I know it's rated HP to weight but, What determines the car weight? Can you pretty much get it as light as possible to fit the class or add to move to another class?
Example:
Corvette weighs about 3400 + 170 with a 350 rated HP motor would be 10.2 lbs. Can you, if you could get the car to say 2950 + 170 with a 350 rated is a 8.91 car. Can you do that much moving from class to class?

[1299]

you take shipping weight and divide that by the hp of the eng you choose.

[ALMACK]

Not sure what the NHRA shipping weight is for your car...but, if it is 3400 lbs: then:

Your natural class @ 10.2 lbs would be GT/E

You could go to D @ 3325 + 170.

So 3495 lbs raceweight would be the lightest ?

From the 2013 NHRA rulebook:

DESIGNATIONS

GT/A, GT/B, GT/C, GT/D, GT/E, GT/F, GT/G, GT/H, GT/I, GT/J,
GT/K, GT/L, and GT/M, preceded by car number (manual
transmission). GT/AA, GT/BA, GT/CA, GT/DA, GT/EA, GT/FA,
GT/GA, GT/HA, GT/IA, GT/JA, GT/KA, GT/LA, and GT/MA,
preceded by car number (automatic transmission).
Reserved for foreign and domestic factory-production two-door coupes,
two-door sedans, sports cars, convertibles, or station wagons with any
production V-8 engine of the same make. Year of engine optional. Only
those engines and/or bodies listed in the Official NHRA Stock Car
Classification Guide are eligible for competition. Also see WEIGHT. Cars
will be classified using the shipping weight of the body divided by the
horsepower or performance rating of the engine used. Factory
production rear-wheel-drive cars must have originally been equipped
with a V-6 or V-8.
Front-wheel-drive conversions permitted. Minimum weight with driver:
2,670 pounds. Only engines and/or bodies listed in the Official NHRA
Stock Car Classification Guide are eligible for competition.
CLASS WEIGHT BREAKS
(based on pounds per NHRA-factored horsepower)
A: 8.00 to 8.49 F: 10.50 to 10.99 K: 13.00 to 13.49
B: 8.50 to 8.99 G: 11.00 to 11.49 L: 13.50 to 13.99
C: 9.00 to 9.49 H: 11.50 to 11.99 M: 14.00 or more
D: 9.50 to 9.99 I: 12.00 to 12.49
E: 10.00 to 10.49 J: 12.50 to 12.99
REQUIREMENTS & SPECIFICATIONS
ENGINE: 1
ENGINE
V-8 only; must be same make as body. Year optional. Engine must
be listed in both the NHRA Stock Car Classification Guide and
NHRA Blueprint Bulletins. Corporate engines permitted. Truck
engines prohibited. Underhood modifications for engine installation

prohibited (i.e., firewall, shock towers, frame, excessive cutting of

[Alan Roehrich]

For GT, the car itself used to be assigned it's highest/heaviest shipping weight. That is the shipping weight you had to use, regardless of what engine you used. So, if you were to swap an LS1 into a car that was originally available with an all iron big block, the natural class of the car would have been calculated from the shipping weight with the all cast iron big block, and the GT factored HP of the engine. They may have changed that rule.

[Terry Cain]

So, Shipping weight would be figured using the heaviest motor available for that yr. car. Correct? So say a 68-75 Corvette would be figured using a BB iron head motor but, WHICH motor? HP is all over the chart for these cars and if you try to calculate using the "weight break" number for any of the BB motors none of the numbers will be the same. Why doesn't the online spec sheet just show a shipping weight?

[Dwight Southerland]

If you tab to the right on the excel spreadsheet, you will see the shipping weights.

[Terry Cain]

Originally Posted by Dwight Southerland

If you tab to the right on the excel spreadsheet, you will see the shipping weights.

Dwight,
I'll be damned if I see it anywhere.

[ALMACK]

Terry:

The shipping wts. are on the right on the classification sheets (in the gray shaded area)

These are the shipping wts for Corvette Coupes:

Heaviest Corvette Coupe (big blocks )

1968...3300 lbs
1969...3384
1970...3424
1971...3485
1972...3492

[Ryck Campbell]

shipping weight of the heaviest V8 for the year, make and model of your car; subtract 250 pounds then divide by the factored horsepower of your engine to calculate the lighter class OR add 250 pounds then divide by the factored horsepower of your engine to calculate the heavier class. You should come up with between 3 to 5 classes that your combination can run. THERE IS NO SUCH THING AS A NATURAL CLASS FOR GT. An example could be as follows:
1973 Corvette coupe with automatic - shipping weight is 3559 so 3559 minus = 3309 or plus 250 = 3809. If you use a 1969 350/255 with OEM heads the factor is 294. 3309 divided by 294 = 11.25 (this combination CAN NOT get to the top of the 11 pound class, GT/GA) so to run GT/GA the car would have to weigh 11.25 times 294 plus 170 = 3475 rounded down from 3477.5. For the heaviest class the car can run is 12.50 class, GT/JA or 3845. Obviously the can can also run GT/HA @ 3550 and GT/IA @ 3695. I hope this helps.

Ryck Campbell NHRA D1 Tech Director
315-335-8295

[Terry Cain]

Found it.
Thanks