PART TWO

Click here to read part one

By Wayne Scraba
Photos courtesy GM/MPR
1/7/05

In a rear wheel drive application, frame rails are moved inwards and tubs are fabricated. That’s no big secret. But in a FWD car, restrictions by both the Rulebook and the car layout determine what can and cannot be done. According to the Rulebook, parts of the OEM strut tower must remain, but as you can see, in order to fit the rolling stock, considerable surgery in and around the tower is mandatory. The reason, of course, is both structural and the need for rubber room.

Suspension, Front: “Upper mounting point for strut assemblies must be in the factory location. Front and rear sides of strut tower may be “notched” for tire clearance and area must be refinished with minimum .024-inch steel. Full wheel tubs prohibited. Roll-bar tubing may run across top of strut tower and attach to frame horn. Adjustable caster/camber pillowball mounts are permitted. Lower control arm may be strengthened provided factory-mounting points to chassis are maintained. Aftermarket or fabricated lower control arms permitted; must use original mounting points. Lower mounting point for strut assembly may be modified for improved caster or camber. Strut tower braces, lower tie bars, sway bars, and limit straps permitted. Traction bars/devices permitted; must be bolt on ONLY. Final decision rests with NHRA Technical Services.”

Since everything is so densely packed in the engine compartment, the solution in this case is to mount the master cylinder under the dash. The master cylinder is perched on a bracket welded to the roll cage brace and activated by a crafty bell crank arrangement.

As you can see, there’s more “stock” here than first meets the eye. Sure the cars are heavily reworked (and they have to be to contain the HP they’re producing), but much of the factory geometry must remain as produced. When you’re examining these Rules, keep in mind that the chassis builder is not only dealing with driving the front of the car, he’s also faced with steering and the previously mentioned packaging requirements.