Pure Stock Prep School Part 2- Pontiac Tech

Leaf-Spring Pontiacs
For leaf-spring cars such as Firebirds, we'll use Tom Miller's Carousel Red '69 Firebird 350 H.O. with a Turbo 400 trans as an example. This Pontiac has a very mild rebuild on the motor and too many options for an all-out PS racer, but has still proven to be very effective. The springs appeared to be in good shape, so we stayed with them, but again, we added Polygraphite bushings. We also chose to run a high-quality 50/50 shock to improve on what we believed to be ineffective shocks.

After arriving at the Pavement Pounders Shootout at Stanton, Michigan, this fall and making a few shakedown passes on the changes, it was decided that we didn't go far enough. Back in the pits, we added additional spring clamps, which go in front of the axle and are applied on the second spring pack right in front of the very bottom spring.

With another check of the tire pressure, the car returned to the track. Bruno Beltrane, another Shootout racer, came back with the report that the little H.O. was lifting the left front tire on launch! This work equated to a best e.t. ever on the Bird by over two-tenths of a second, most of which came in the first 60 feet.

All Cars: Sway Bar
The last suspension item that needs to be adjusted to help the suspension changes achieve their full potential is the sway bar. The front sway bar needs to be loosened to allow full range of motion without binding. For safety reasons, don't just loosen the two sway bar brackets on the radiator support or frame, but rather add one or two washers between the body and bracket, which allows you to fully torque the bolts. With the sway bar properly free to move, it will allow the front of the car to more smoothly rise on launch, transferring weight to the rear tires more efficiently.

Tires
The items that tie together all the hard work you've done and make the final connection between the car and track are the tires. As can be noticed from the PS series of the "Pavement Pounders Shootout," virtually all the fast Pontiacs run on bias-ply tires instead of radials. The problem that competitors have found with tires such as BFGoodrich Radial T/As is that when they start to lose grip and spin, they stay spinning and provide little forward motion while doing so. The bias-ply tires still pull during a spin in comparison to radials.

You can choose from either Goodyear or Firestone. Both seem to work equally well, but they tend to differ in height and width, when comparing similar sizes. If you're running a '701/2 Trans Am, you need an F60x15 tire. The Firestone spec is 25.9 inches tall and the Goodyear spec is 26.27 inches tall. This may seem modest, but if you're staying with a 3.55 gear you may take advantage of the shorter Firestone to give you just a bit more effective gear ratio. These are the little things that need to be taken into account while studying which tire to choose.

After the tire is mounted and you're ready to race, you need to find the correct pressure. Bias-plys tend to run counter to everything you've learned with radials. Instead of lowering tire pressure, you actually raise it. In the front, it's best to be in the 45-50 psi range to lower rolling resistance. In the back, tire size and aspect ratio will drive the choice. When using 70-series tires, like most A-bodies and First-Gen F-bodies, run pressure in the 40-42 psi range. The 60-series tires for Second-Gen Birds and late GTOs can run with less pressure. Start in the low 30 psi range and, depending on application, you may need to go as low as 28 psi.

The tire pressure will need to be checked after your first few runs, as it will have risen from the heat that has been put into the tires from the burnout and race. Occasionally, with the heat of the day and runs, they'll have to be readjusted.