READERS CHOICE

  NEWS & FEATURES

  DEPARTMENTS
   Staging Light
   Reaction Time
   Bits From The Pits
   On The Run with ...
     Chuck Etchells
   On The Run with ...
     Shannon Brinkley
   Racing Technology
   Be A Winner Scorecard
   Bracket Racing North America
   Membership Midway
   Hoosier Scorecard
   NHRA Top Performers
   Running Healthy
   NHRA InfoGuide

STAFF

BACK ISSUES

by Wayne Scraba

Some cars, such as GM's newest F bodies, can peel corners with the best of them. Lateral acceleration figures in the high .8+ G zone aren't out of the question, and if that isn't enough, plenty of support and equipment are available from the aftermarket. That's wonderful, but if you drag race, corners don't count.

Because of this, along with some prodding from readers, I decided to share some of my drag racing R&D. Here's a bit of background: In the not-so-distant past, I built a new Firebird for Stock eliminator, for which the NHRA Rulebook mandates bolt-on hardware. That means that tubs, four-links, wheelie bars, and wall-to-wall rubber are out. In simple terms, a Stocker has to hook with a little slick. Because I had already completed tons of research and made an equal number of mistakes, it seemed like a good idea to present this to you firsthand.

Of course, it's no secret that Stockers don't pack the biggest punch in drag racing — after all, they're pretty much restricted in terms of engine and chassis modifications — but that doesn't mean they're slugs, either. A good NHRA-legal LT1 will produce between 445 and 465 horsepower, enough to drive a late-model combination deep into the 10-second zone.

If that isn't sufficient proof, look at the e.t.s turned by lower-class ('82-'92) Camaros. These cars use an identical OEM torque-arm rear-suspension arrangement, and even with small-displacement, carbureted 305 powerplants, they still knock off 11.70 or quicker passes.

What follows is a look at what and what not to do with regard to front-suspension systems; rear-suspension systems will be covered later. Though the information focuses on late-model GM products, much of it can be used on any car. Yes, I am giving away a couple of not-so-privy secrets, but, perhaps more important, I'm letting you in on all of my mistakes:

Upper and lower control arms
If you do some research, you'll find that the control-arm bushings used on a new Camaro or Firebird aren't serviceable. The bushings are serviced only by purchasing new control arms. Obviously, this isn't good from a straight-line perspective. There is an answer, and it's a good one. But first, let me explain: Initially, I built the front suspension on the car with common replacement urethane bushings designed for these cars. Though primarily designed for use in "handling" applications, they appeared well-suited, at least initially, for drag racing.

The bushing-replacement job is miserable. You'll immediately find that these bushings don't come out easily or with a hammer. The best method involves heat, and in most cases, plenty of it. The outside of the bushing shell is heated with a propane torch, then driven out with a hammer. Once this is complete and the new urethane bushings are installed, the suspension can be reassembled. I did that, then completely assembled the suspension in the car.

A system of testing the breakaway and constant torque required to move the suspension through its travel without a spring or shock installed was devised. Basically, it involved the use of a makeshift fixture and a beam torque wrench. To my dismay, it took well over 50 foot-pounds of torque to move the suspension through its travel and consumed far more breakaway torque to get the suspension moving. What I had stumbled onto is what Penske and other shock-absorber manufacturers call "stiction." And it's not a good thing.

When the suspension system in a race car has stiction, it means the shock can't do its job effectively. In reality, the bushings I used were sticking due to friction during suspension travel. This also meant that as the bushing heated or cooled, the amount and rate of travel available in the front suspension changed, often by dramatic margins. Additionally, it meant that the shock-absorber settings could never be the same from one lap to another. In simple terms, the bushings were doing much of the job the shock was supposed to handle but without any consistency or any adjustability.

To solve the problem, chassis builder Alf Wiebe, Aurora Bearing Co., and I came up with an arrangement where the lower control-arm bushings were replaced with high-misalignment spherical bearings. Without going into detail, a special sleeve was fabricated to take the place of the OEM bushing sleeve in the control arm. From that point, a high-strength spherical bearing could be used to replace the bushing. The upper bushings were effectively loosened by lightly honing the inside diameter; you also have to keep in mind that the torque required on the fasteners that hold the components in place does not change — only the torque required to move the suspension system changes. We ended up with a breakaway torque of less than five foot-pounds without a spring or shock mounted in the front-suspension system. In simple terms, it was loose as a goose.

So how can this arrangement that works in a '93 or newer Firebird be adapted to other cars? Actually, most other Stockers, no matter what the make or model year, are far easier to deal with. The aftermarket offers non-serrated control-arm bushings for a large number of early cars, and for others, many metal and nylon (not urethane) bushings are available that accomplish the same "loose" goal. What you need to do is to mix and match components so that you end up with minimal friction as the front end goes through its travel without a shock or spring in place. Just remember that it's not a good idea to compromise reliability for movement. Use good hardware. You won't be sorry.

Travel is everything
Front-suspension travel is important. Here's how to get it: Though not found on very late Firebirds or Camaros, most early GM cars and several other Detroit marques feature a system of limiting the downward movement of the front control arms. In a race car, especially a low-horsepower race car, you need as much front-end travel as possible. Short of adding some ball-joint extensions, which are illegal, there is a way to increase front-end travel in these vehicles.

The manufacturers often used a rubber snubber mounted to the upper control arm or front framerail to limit A-arm travel. This snubber is very similar to a conventional slapper-bar snubber. If the snubber is trimmed, the front end of the car will exhibit a much more favorable travel arrangement. Just keep trimming the snubber until the car slows down; of course, in some cases, you'll have to remove the snubber altogether. If you trim too much of the snubber, swap the snubber for a common traction-bar component. Too much material can be cut away — watch the brake flex line. If it's stretched during full travel, you've gone way too far.

Front stabilizer bar
It's no secret that almost all rear-wheel-drive cars used in Stock eliminator incorporate some form of stabilizer or sway bar. But as mentioned, in drag racing, corners don't count. The front bars restrict control-arm movement, effectively linking both sides of the front suspension. When disconnected or removed entirely, it allows the suspension to rise and fall rapidly, which translates into better launch capabilities. In the case of a Stocker, the answer is simple: Dump the sway bar. Removing it is simply a matter of peeling out fasteners and removing the bar.

Soft springs
In the March 19 issue, I provided a detailed account of drag race springs. In a car such as a Stocker, springs are critical. The following is a short review. Front springs built especially for drag racing feature added coils, a longer overall length, and slightly smaller-than-stock wire diameter. This configuration allows the spring to store energy. While stationary, the car remains level or, in some cases, has a slight forward rake, but when the throttle pedal is mashed to the floor, the nose of the car will rise rapidly. While accelerating in the upper gears, the springs settle down quickly, dropping the nose of the car to a much more aerodynamic profile.

Drag race front springs are available in a wide array of configurations to fit a number of varied applications. Be forewarned that the nose will rise rapidly and the car will have a tendency to dive hard under braking. As a result, weight is quickly transferred to the rear of the car, where it will do the most good in terms of quarter-mile elapsed times.

The three truths of wheel alignment
Front-end alignment is important, and it carries with it a new set of truths. They're terms racers seldom discuss. In reality, all three deal with geometric angles. Here's the inside story.

Caster: Caster is the backward or forward tilt of the spindle as you look at it from the side of the wheel and tire combination. When caster is positive, this means the wheel assembly tilts backward, which in turn places weight behind the tire-contact patch. When caster is negative, the top of the spindle is tilted forward, which places weight in front of the tire-contact patch.

Caster is expressed in degrees and measures the amount the centerline of the spindle or, in the case of a solid axle, the kingpin, is tilted from true vertical. Typically, caster figures seldom go beyond -3/4 degrees, and in almost all high-performance applications, some amount of positive caster is required. Why? Simple. Think of positive caster as a means to self-center the steering. If you're familiar with bicycles, that's why touring bikes have a fork that's kicked out. It provides a big chunk of positive caster, which in turn gives the rider a lot of directional stability. In contrast, a mountain bike has a fork that's much closer to vertical. It provides lightning-quick turns but very little directional stability. You can easily ride the touring bike without your hands on the handlebars, but not the mountain bike.

Camber: Think of camber as the tilt of the wheel at the top, tilting in or tilting out. Camber is expressed and measured in degrees and looks at the tilt of the wheel from true vertical. Pretend that the wheel and tire combination tilts out at the top. This means the camber is positive. If the top of the wheel tilts in, the camber is negative. The real idea behind camber is to keep the tire planted squarely on the tarmac. This in turn creates maximum tire grip and overall front-end traction. In theory, it sounds as if zero degrees of camber is good. That isn't the case in the real world, though. Most cars require different camber figures while at rest so that good grip and tire wear are maintained as the car travels down the road. Typically, a car with a small amount of negative camber will exhibit better dragstrip handling characteristics without killing the tire.

Toe: Toe, whether in or out, is the difference in distance measured across the face of the front tire and that of the trailing end of the same tire viewed from head on. Toe-in creates a pigeon-toed look with the front of the tires pointing inward. Toe-out is just the opposite with the front of the tires pointing out. The actual toe setting is seldom zero. In most street car applications, a small amount of toe-in, usually 1/16- or 1/32-inch, is common. Why? Because as the car moves down the road, the dynamics present on all of the steering and suspension components tend to force everything outward. This results in almost zero toe as the car is in motion.

Dialing in caster, camber, and toe
In the chart that follows, we've compiled GM's wheel-alignment specifications for late-model F platforms. If you decide to drag race such a car, try adding a bit more caster, up to six degrees if you can. Keep an eye on the toe change while the car is jacked through its travel. Toe-in change must be kept to a minimum. The last thing you need is toe-out; this usually isn't a problem with the front suspension on the new Firebirds and Camaros, but it can plague some earlier cars.

Before you do a wheel alignment on any drag car, place weight in the driver's seat that is equal to the driver's weight. Shot bags or weight-lifting equipment will work. Be sure to top the fuel tank with the appropriate level of gasoline. Set the tire pressures to the level you normally race with (i.e., high pressure on the nose and lower at the rear). With the car on the alignment rack, jack the nose up to duplicate a normal race attitude — an inch or two seems to be about right. The car is ready for the alignment. Remember that every car will be slightly different; the chart above shows the OEM alignment figures:

Because every car in competition will be different, use the following basic guidelines for wheel alignment.