W/TH in NHRA classification?
 

Hi All,
hope you can help with our query. We have just finished preparing a 1970 Camaro with an LT1 and hope to be racing it here in Sweden in D/SA next season, but when establishing the legal weight we come across different shipping weights depending on whether it's a "coupe 2 door" or a "coupe 2 door W/TH.
I initially thought TH stood for TurboHydramatic, but the different weights appear also under "manual transmission", so what does the TH stand for?

350 350
* *
auto manual
360 360

3341 3341
3397 3397

325 320
12.19.02 1.1.15

Re: W/TH in NHRA classification?
 

w/TH does stand for "with TurboHydramatic". In the case of your '70 Z-28, the car would have been factory equipped with a Turbo 400 which was heavier than the manual transmission. Just for an understanding about the differences in weight, back during the years of most of the Class Guides, manufacturers had to supply relatively accurate shipping weights to freight companies for proper charges of their services. So, depending on the equipment on the car, the "shipping" weights changed. If the car was equipped with V8 engines, air conditioning or disk brakes or other options, the manufacturer calculated the shipping weight to give to the freight companies. The added weights were usually published in AMA (Automobile Manufacturers Association) specifications and you can find examples in those publications. NHRA generally assumed that the racers would use no options cars for competition so the shipping weights were generally the minimums. In the case of the automatic transmission equipped cars, since they would be in classes where the car would be required to have that option, the additional weight was added to the minimum shipping weight for classification. Sometimes the NHRA Classification Guide used the shipping weight differences for calculation and sometimes not.

Re: W/TH in NHRA classification?
 

Your horsepower factor is 325 with an automatic or 320 with a stick. Minimum weight in D/SA is 3255. with a stick it's either 45 or 50 less. The w/th is with an auto, stick shipping weight is lighter.

Re: W/TH in NHRA classification?
 

Thank you Dwight and Greg, is the 3255 lbs plus 170 lbs for the driver or including driver?

Re: W/TH in NHRA classification?
 

From what I read, class is determined without driver and then 170 is added for total weight. Total weight, I think, is what you have to be at on the race scales.

Re: W/TH in NHRA classification?
 

That's with the driver. 325hp x 9.5 + 170lbs = 3255lbs.

Re: W/TH in NHRA classification?
 

A local racer has also told me class is with racer weight, but the book says no. Who is right?

Re: W/TH in NHRA classification?
 

NHRA/IHRA allows 170 lbs. for driver.

Example, a G/SA that pencils out to 2,970 must be 3,140 across the scales with driver.

Re: W/TH in NHRA classification?
 

The weight you must be equal to or greater than , when you go across the scales is called the "minimum weight" . It is usually equal the min Class weight break times your factored horsepower , plus 170 . The exception to this is then you try to change classes up or down , you can only adjust the weight by 250 lbs. from your natural weight break , which is found in the NHRA Classification Guide .

Re: W/TH in NHRA classification?
 

Thank you all, I now have it clear in my head. This is the class my wife Carla will race in, as we her car is now Stock legal after spending many years in bracket racing.
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