A BAR TO THE RESCUE

Do you need a rear antisway bar on your muscle car? If you’re praying when you launch, maybe you do.

❱Trick question: What’s the difference between a sway bar and an antisway bar? Absolutely nothing. The linguistic shorthand of gearheads has abbreviated the more accurate term, antisway bar, in a way that mirrors the equally ambiguous role that this important suspension part plays in drag racing. (Note that in MotorTrendnew-car speak, this part is referred to as an “anti-roll bar,” which, though correct, may cause confusion to drag racers who know the part as an “antisway bar.”) A rear antisway bar is the kind of part that is seldom pondered until you realize you need it, which is a good measure on which to base your need. We realized we needed one for our long-term 1968 Plymouth Valiant project car years ago, and we’ve put it off for too long. Nevertheless, we’ve some serious explaining to do before we dive in.

Mopars, which have a leaf-spring rear suspension, are probably the least likely cars to need an antisway bar for drag racing. They almost never need one—unless they’ve been converted (like ours) to a suspension type used mostly by GM and Ford called a triangulated four-link. This is the type of rear suspension used in the Ford Mustang from 1979 until 2004. It’s also the same one used in GM intermediates (A-body and G-body) from 1964 to 1988, and in full-size GM B-bodies over their entire lifetime. Other rear suspension types, like the torque-arm suspension found in GM F-bodies (1982-2002) and the three-link found in 20052014 Mustangs, also benefit greatly from a rear antisway bar.

REAR ANTISWAY BARS: WHO NEEDS ’EM THE MOST?

Forget for a moment that our subject vehicle is a 1960s Mopar—it might as well be a 2003 Mustang Cobra or a 1980 Chevy Malibu wagon. Our car suffers from the same ailment called the “G-body shuffle” by many a grudge racer, and we’re here to tell you how to deal with it successfully. So if you’ve got any one of these vehicles with a triangulated four-link, GM torque-arm suspension, or Ford threelink, listen up: The diabolical handling you’ve experienced at launch and down the dragstrip isn’t in your imagination, it’s not about you being a bad driver, and it’s not about having too little air pressure in your tires. It’s about controlling and counteracting the body roll your engine’s torque is causing.

located laterally, which further reduces body sway. Leaf-spring cars can suffer from other problems like axle wrap, tramping, and wheelhop, (usually solved with a pair of Calvert Racing Caltracs bars) but generally not body sway or body roll.

Why This Mopar Needs An Antisway Bar

In this image taken during testing at Fontana’s quarter-mile several years ago by EngineMasters’Steve Dulcich, you can see the body roll in our 1968 Plymouth Valiant subject car, which is equipped with a Reilly Motorsports four-link coilover rear suspension conversion. When launched with the full force of its 650hp

DO MOPARS NEED A REAR ANTISWAY BAR?

Let’s go back to Mopars for a moment and see what’s happening there. In this photo of Mike Clifford’s mid-10-second 1966 Plymouth Barracuda we photographed a couple years back at Lights Out 11, you can see the body has not rolled over on its right side at launch. Mopar engineers fixed this a half-century ago with stiff, over-the-counter Super Stock leaf springs that limit vertical suspension travel. The right-side spring has more lift at rest so that when the axle torque hits it at launch it’s preloaded to go straight. There’s also a nifty adjustable pinion snubber that helps leverage the axle away from the right side of the body and limits axle wrap at launch. The leaf springs also do a great job of keeping the axle big-block Wedge, the left rear tire jams into the pavement while simultaneously lifting the right rear resulting in a hard uncommanded turn to the right. This sets off a periodic swaying that arises from the steering input needed to keep the car going straight. Eventually, the run is terminated for safety reasons as the car’s swaying only gets worse as the speed increases.

When The Body And The Axle Go Different Directions

In the diagram you can more easily see the dynamics of what’s happening in a dragstrip launch. When engine torque is applied to the axle, it rotates the axle counterclockwise, as seen from behind. Since the engine torque is applied to the body through the engine mounts in the opposite direction, the body rolls in a clockwise fashion. In drag racing, where the idea is to go as quickly as possible in a straight line, this creates a lot of problems with vehicle stability and safety as it almost guarantees that a high-powered car like this is going to move out of the racing groove and become hard to control. At this point, the advantages of the four-link’s lower unsprung mass, improved ride quality, range of motion, and pinion-angle stability is moot—at least on the starting line of a dragstrip.

Rear Antisway Bars Are Available For Many Drag Cars

Fortunately, solving this problem is an easy one if you don’t mind a few hours of work adding an antisway bar. If you’ve got a Mopar with a Reilly Motorsports Street Lynx rear suspension, the kit we’re installing is available from RMS for $395. If your Mopar has a four-link conversion kit from QA1, then you’ll want to check out their Mopar rear antisway bar kit for $352.95. Competition Engineering offers a very popular drag rear antisway bar kit for universal and Ford Fox-body Mustang applications and BMR (shown at right) has a comprehensive line of drag antisway bar kits for all the usual four-link suspects including Mustangs. Rhodes Race Cars is another company with a great universal kit, and AJE Suspensions—the biggest long-haul player in fast Fox-bodies—has a constellation of kits for a bunch of GM and Ford four-link designs. When your triangulated four-link street/strip machine starts showing signs of schizophrenia on the starting line, you’ll know where to go for the Rx!

The Rms Rear Antisway Bar Kit For Mopars

The prescription for our A-Body Mopar, however, is a Reilly Motorsports unit designed specifically for that company’s Street Lynx rear triangulated four-link coilover suspension conversion ($395, shown). The kit consists of a solid 3/4-inch diameter steel bar with welded flanges on each end for a pair of bolt-on bellcrank levers. (A 5⁄8-inch hollow bar is available for road race and autocross use.) The bar is attached to the axle via mounting brackets with urethane bushings and to the frame by means of adjustable endlinks that pivot off the lever arms. Finally, a pair of aluminum collars allows the bar to be centered between the coilover mounting brackets. We found the kit well engineered, and it did not interfere with any important things such as wide tires or exhaust.

Bishop Custom Cars

Helping us with our Valiant’s antisway bar kit installation was Eric Bishop of Bishop Custom Cars in Palm Desert, California (442.666.8621), a shop in California’s Coachella Valley with a lot of experience building custom chassis and fast hot rods. Bishop fabricates a lot of serious machinery, which turned out to be overkill for this job, but we wanted the best in our area just in case something needed a little professional persuasion. Thankfully, the RMS kit was a breeze for Eric to install, only taking him four hours— including the replacement of our old control arms with new ones containing upgraded Johnny Joints for less axle movement. (We’ve used Johnny Joints successfully in Currie Enterprises line of GM A-body control arms on an 11-second big-block ’68 Chevelle over a decade ago, but the company no longer offers these A-body control arms.)

INSTALLING AN ANTISWAY BAR KIT IS EASY AS 1, 2, 3 …

Before starting, lay all the parts out and bench-assemble the antisway bar setup so that the corner assembly looks like this. The lever arms bolt onto the outboard side of flanges welded to the bar with three bolt sets on each side, and the arms are oriented to bend outward toward the tires. The adjustable-length endlinks are mated inboard of the levers and the aluminum sleeves locating the center bar are sequenced between the axle bushings and the lever arms.

This view shows the layout of the RMS Mopar Street Lynx triangulated four-link coilover system prior to getting the antisway bar. Note that the antisway bar does not come with the basic Street Lynx rear suspension kit. Four-links like this have an advantage over simpler leaf springs because they take a bunch of unsprung weight off the rear axle, making road irregularities easier to swallow. Pinion angle is also well controlled and lateral motion of the axle is eliminated. The only downside to a triangulated four-link is its misbehavior on the dragstrip starting line. Other cool pieces of hardware here include a 3.54:1-geared Strange Engineering S60 rearend, Viking double-adjustable coilover shocks, Wilwood 11-inch fourpiston Dynapro disc brakes, and TTI exhaust with Dynomax Super Turbo mufflers.

the right side of the bar, lifting the bar into place to bolt the right side on last. The bar is bolted on, but still must be centered. This is not preset in the bar’s design because the axle location and rear framerail position are slightly different in every car, including ours. Here, Eric is pointing to the two billet aluminum sleeves that will be tightened once you figure out where exact center is. This is achieved by rotating the ends up toward the framerails where you plan to mount the endlink tabs; you may discover the bar needs to be moved over a little to one side to make things symmetrical. (Fourth-gen GM F-bodies are notorious for having a left-offset pair of rear framerails.) This procedure will be similar for any of the antisway bar kits on the market for any model of car.

Here’s the moment of truth when you get to find out how well the product is engineered. Does everything line up? Does it fit? Will we need the full arsenal of Eric’s fabrication chops to get us through the day, or will beer-thirty happen early? Due to the fact this antisway kit was designed specifically for the RMS suspension, everything matched up perfectly with no surprises, as you’ll see.

The RMS Street Lynx system employs axle brackets that serve as pick-up points for the lower control arms, the Viking coilover shocks, and pivot bushings for the optional antisway bar kit. The holes for the bushings already exist on the axle brackets so it’s just a matter of bolting up the hardware. Eric mounted the left-side bushing first, slid the bar into the left side, then put the bushing on

The only welding you’ll need to do is for mounting the endlink brackets to the framerails. Here, Eric has positioned the bracket where he wants it and is marking the bracket’s outline on the framerail with a marker.

Using a Millermatic 211 MIG welder with Auto-Set (one of our favorites), Eric had our endlink brackets stitched to the Valiant’s rear framerails in no time. For this operation, you’ll want to prep the surface for welding by removing any paint or undercoating so that you get a solid weld with good electrical conductivity.

A quick coating of Dupli-Color acrylic enamel in Satin Black protects the bare metal against corrosion and matches the existing chassis black. Note how the bracket is positioned so that the endlink translates motion to the antisway bar lever vertically.

One thing you get with dragspecific antisway bar kits like this one is adjustability. Factory triangulated four-link suspensions typically use C-shaped bars made in a tubing bender. These bolt directly to the lower control arms—when they’re present at all—and don’t have the preload adjustability needed for drag racing. By contrast, this type of antisway bar (which uses bell-crank levers) allows the endlink to be lengthened or shortened on either side. This means you can compensate for any unevenness between sides, or you can add preload to the right side when you get to the dragstrip. Here, Eric shows how easy it is with the built-in “flats” for a tool on the lower portion of the endlink.

If a picture can tell a thousand words, then this one is worth a closer look because you can see how the antisway bar would control how flat the rear of the car handles—whether accelerating hard in a straight line or going flat around corners. Before we added it, the back end of this Valiant would wander and sway all over the road under hard acceleration (i.e., long, lurid burnouts) earning it the nickname “the widow-maker.” Now when we step on the gas it doesn’t require a bunch of whip-sawing on the steering wheel to keep it in a straight line. (We like not making the epic-fail highlight reel at Cars and Coffee.) We felt the difference immediately and dramatically—as in, there’s no more drama. It just hooks and books. All we can say is we should have done this years ago when Fontana’s dragstrip was still open!