Conclusion
All the tools to be a fast Pure Stock racer have been laid out over the past two articles. Even if you never intend to join us at the track, these tuning aids can be applied to your show car so that it's capable of peak performance at the next cruise night. Before shopping for speed parts, take some time to apply these suggestions and see how quick you can go with a stock Pontiac. Most Pontiac musclecar combinations, with some determined tuning, can achieve 12- and 13-second e.t.'s. Now that's real pavement pounding performance.
The Pure Stock Muscle Car Drag Race Rules, Continued
Last month we covered the rules for the engine, exhaust, and cooling systems. This month, we look at what is allowed and what isn't for the rest of the drivetrain (transmissions, driveshafts, rear axles), wheels, tires, the front and rear suspensions, and the body, including the interior.
Automatic Transmissions
The transmission and the torque converter have to be correct for the year, model, and horsepower claimed. For example, a '66 GTO is required to run the two-speed Super Turbine 300, not a three-speed Turbo 350 or 400. We allow shift improver kits, but neither lightweight internals nor aftermarket shifters are allowed. High-stall torque converters are useless on our cars since we run street tires, so the limit is 2,400 rpm.
Manual Transmissions
Cars with floor-shift three-speed manual transmissions can be upgraded to a four-speed, if the four-speed was originally available as an option. Aftermarket H-pattern shifters are allowed as long as they don't require modification to the floorpan or transmission tunnel. Inline or "vertigate" shifters aren't allowed. Cars that were only available as a column-shift can't be converted to floor-shift. (This goes for automatics, too.) No "crash boxes" allowed. OEM or aftermarket OEM-type clutches only, no "slipper" clutches.
Driveshafts
Stock steel driveshafts are required and we allow the use of stronger (larger diameter) steel driveshafts, but no lightweight driveshafts (aluminum, carbon fiber, etc.). Driveshaft safety loops are required on any car that runs 13.99 and quicker.
Rear Axles
The rear axle has to be of the same manufacturer as the car. That means you can use any GM rear axle in your GTO, like the 12-bolt out of a comparable Chevelle, but the track dimension can't be altered from the original. Any gear ratio is allowed.
Wheels
Factory wheels have to be correct for the year, model, and horsepower claimed. All four wheels must be the same size, and have the correct offset. Aftermarket wheels aren't allowed, including Hurst Wheels. Sorry!
Tires
Tires are limited to either correct-size reproduction bias-plys or equivalent-size street-spec radials-no soft compound tires. We do allow cars built before the introduction of 70-series tires to run these on their cars. For example, owners of '64-'66 GTOs can upgrade to the reproduction F70x14 tires (like the '67 GTO), or an equivalent-sized radial tire. All four tires have to be the same size (the only exception being the '70 AAR 'Cudas and T/A Challengers that had one size larger tires on the back from the factory).
You can't use 60-series tires unless they were originally available for the car's year, make, and model. As far as we recall, all factory 60-series tires came on 15-inch rims, so no 14-inch, 60-series tires are allowed. For Pontiac lovers, only the '71-'73 GTO and the '701/2-'74 Formulas and T/As can run 60-series tires on 15-inch rims.
We do allow cars to run tires one size larger than stock, with the "G" size being the largest allowed in both 60- and 70-series. For example, the '67 GTO came with F70x14 tires originally, but we allow the car to run G70x14 tires. The '71 GTO came with G70x14 tires from the factory, so it's already equipped with the largest 14-inch tires we allow. The owner of the '71 GTO has the option to upgrade his car to the G60x15 tires and 15x7 Rally IIs because they were available that year as an option.