Pure Stock Prep School Part 2- Pontiac Tech

Exhaust
The exhaust system is your last drivetrain issue to address. How important is the exhaust? Very! The Ram Air IV Judge in the lead shot of the last installment is a good example. The previous owner used it as a show car and we were going to use it as a race car. Its NOS exhaust system and factory-spec engine only allowed 13.90s at 105 mph. With a change to an X-type pipe system, the car went 13.13 at 111.8 mph.

To achieve the best results, you'll need to start with an all mandrel-bent 2.5-inch exhaust. Next, you need to decide whether to use an H-style pipe or an X-type pipe. Each has its own merit.

Most racers have adopted the X-type pipe system. It provides excellent scavenging in the low to upper midrange. At very high rpm, it's not as effective. Most PS cars run completely in the rpm range, where it does its best work. The one exception is the Ram Air IV, but even this motor, overall, is well served by the X-type, as it provides additional bottom end and midrange that the engine lacks on its own.

The H-style pipe has been a staple for decades, and is still a viable choice. It does a nice job of balancing pressure on each cylinder bank while providing superior scavenging at high rpm. The drawback for PS racing is that most of the H-pipe's advantages over an X-type don't start until 5,000-plus rpm, and is most beneficial over 6,000 rpm.

There aren't too many Pontiacs in our race trim that turn in the high 5,000 range. The one place they've worked well is with motors that already make lots of torque, such as the 455s. Compared to an X-type, the H-type pipe will slightly soften the bottom and midrange and give the mighty 455 a touch of extra top-end power. This actually has been and can be used to an advantage to make the 455 more manageable for traction early in the race, but also lets it finish strongly at the traps.

Suspension
Suspension becomes the lynch pin to all the drivetrain choices that have been discussed. At first glance, it appears that not much can be achieved by looking in a rule book that says we must stay with 50/50 shocks, stock spring rates and factory-correct sway bars must be present and functioning. In reality, however, this is where it all comes together and all the fastest Pontiacs are created.

Coil-Spring Pontiacs
Let's use two examples to prove the merit of detailed chassis setup. Both cars are veterans of the Pure Stock drags. First, let's discuss the Pepper Green Judge. This car was struggling to get into the 12s. It made tons of power and was hitting big mph, but its launch performance and traction after each shift were disasterous. The factory-spec motor was supplying enough power to run near 112 mph, but the all-original suspension was incapable of handling it.

We decided that the hunkered-down stance the worn-in suspension was supplying was desirable, so we kept the factory springs. Next, we looked at the used spiral shocks and decided they were providing plenty of front-end lift, so we chose to keep them also.

The first big change came in the form of new Polygraphite bushings to let everything move freely and to provide firm control against unwanted flex. Then we employed a set of Hop Stop bars, which is the only non-factory spec item allowed for coil-spring cars in PS racing. The first time out on this lightly modified suspension garnered a 12.802 at 111.86. This combo now supports low 12-second runs with the new motor. If your shocks and springs are beyond use, replace them. In our case, we haven't had to-yet.

Hop Stop bars tend to work best on four-speed cars. Dan Jensen's 455 H.O. T-37 with an automatic doesn't use them and he has run 60-foot times as fast as 1.8 seconds. The way automatic cars meter out the power, they don't seem to garner the benefit four-speed cars gain. The biggest reward for Hop Stops has been with the high-winding violent R/A-II and R/A-IV GTOs.