You've probably seen the television commercials that feature these incredibly overweight people who have lost 150 or more pounds. They all say the same thing: "This has changed my life." When it comes to high-performance street cars, there's nothing more lifestyle changing than a serious suspension upgrade that converts a strictly straight-ahead machine to one that can now negotiate corners with impressive control. Let this be said: Turning corners is fun.
Last month we introduced you to Shannon Hudson's lime-green '69 Plymouth Valiant when we outlined regearing his 83/4-inch rearend from 4.10:1 to 3.55:1. At the same time, John Hotchkis of Hotchkis Performance was looking for a car to test his new line of Mopar suspension components on for the popular A-Bodies, such as the Dodge Dart, Dodge Swinger, and Plymouth Valiant models. Hudson's bright-green cruiser offered the perfect opportunity, and we soon found the green beast slogging its way through a Hotchkis baseline test at Willow Springs' Streets of Willow track. With a drag race package that included skinny fronts and drag radial rears, the Valiant was, as we expected, underwhelming on the skidpad and 600-foot slalom course.
Next, it was off to the Hotchkis Performance shop where chief engineer Aaron Ogawa designed the 69 Plymouth Valiant upgrades to minimize the compliance as well as a little body roll on the way to a superior-handling suspension. The conversion would also include swapping to a set of front and rear Right Stuff disc brakes, a quicker Flaming River manual steering box, while riding on a set of General UHP tires and a beautiful set of Curtis Speed wheels. We won't go into the boring details of how to swap all these parts since the installation is virtually a bolt-on with the exception of the weld-on sway bar brackets. We'll hit the important bits and concentrate more on how all these parts integrate to transform the lime-green Mopar into an excellent-handling road car that Hudson will now use to attack those twisty mountain roads just north of his shop.
69 Plymouth Valiant - Front-End Chemistry
Mopars are somewhat unique in the front suspension area with their use of torsion bars, which are really nothing more than straightened coil springs. The torsion bar is mounted into the narrow lower control arm that is triangulated with a strut bar, much like an early Mustang front suspension. Add in an upper control arm to locate the top of the spindle and you have a basic A-Body front suspension. Hotchkis' goal was to improve on this basic system by removing as much rubber as possible while adding additional caster and camber to allow planting the front tire to optimize traction in the corners.
69 Plymouth Valiant - Bringing Up the Rear
If the front suspension was easy to install, the rear is even easier. The Hotchkis springs are significantly different from the previous Mopar Performance Super Stock drag race leaves that had one additional leaf on the right side. All Mopar leaf springs are asymmetrical, meaning the portion of the spring from the housing to the front spring eye is shorter than the rear. This automatically strengthens the front spring section to virtually eliminate wheelhop. The Hotchkis springs are the same rate side to side to make handling more predictable but also reorient the way the springs are placed on each leaf. The main leaf in stock springs is the one that connects to the pivot on both ends, but the Hotchkis springs assign that job to the second leaf, using the top leaf as a reinforcement to minimize main leaf wrapup. The Hotchkis spring is rated at 130 pounds per inch (lb/in), while the Mopar drag springs use two different rates, with the passenger side measuring an average of 170 lb/in and the driver side at a slightly lower 160 lb/in. Hotchkis also includes a new four-bolt front spring eye hanger that raises the front spring eye location to reduce roll steer.
Disc Brake Conversion
Right Stuff Detailing makes a simple yet effective disc brake conversion for the early A-Body cars that bolts on with very little effort. The kit comes with the spindles and is also shipped with new upper control arms to accommodate the different ball joint, which we didn't need with the Hotchkis tubular arms. The Right Stuff kit comes with all the necessary components, including new wheel bearings, seals, 11-inch rotors, loaded factory-style iron calipers, caliper brackets, stainless hoses, clips, and even an adjustable proportioning valve. The best part was that the company was able to ship these parts to us very quickly. And since most of these parts are kept in stock, you can expect to get the same quick service we enjoyed. The prices listed in the parts list reflect the cost savings of not needing the stock upper control arm and the additional cost of the powdercoated calipers and drilled rotors.
Rolling Stock
The key to making any car handle to its ultimate potential is to create the best symmetry between the suspension and the tires. A great set of tires and wheels will fare poorly with a lame suspension, while even the best suspension components are limited if used with ancient tires. We did a little measuring and discovered that we could actually fit a 275/40ZR17 tire under the back of this little Mopar, so the call went out to General Tire for a set of Exclaim UHP hoops, including a slightly smaller 245/40ZR17 for the front. We chose the General tires for their great handling qualities and affordability. We could have gone with much stickier tires, but that would have been more costly and reduced tread life. The General Exclaim UHPs offer a treadwear rating of 380 (which means they're relatively long-lasting tires) along with an A traction rating. Best of all, the entire set was just less than $550.00.
After measuring tire clearance several times and then double-checking our work, we were rewarded with a complete set of General tires and wheels that bolted right on with no problems. The key to fitting the larger 275/40ZR17 rear Exclaim UHP tires is the 5.5-inch backspacing on the Curtis Speed 15x8-inch wheels.
The next challenge was to fit those tires under the car with no interference. Unfortunately, we couldn't be sure until installing the front and rear suspension conversions and disc brakes. This left us very little time, but Curtis Speed Wheels came through with a set of 17x8-inch cast center Vintage wheels with a very specific 5.5-inch backspacing front and rear that positioned the tires perfectly inside the wheelwells. Ideally, the 275 rear tires should be mounted on a 9.5- to 10-inch-wide wheel, but the next step up with the Vintage wheels is 10 inches, which would probably have rubbed, requiring expensive sheetmetal surgery, so we decided on the more conservative 8-inch wheel width. We want to especially thank Mark Curtis for helping us out on very short notice with a set of outstanding-looking wheels.
Track Testing
The sad part about this story is that you can't get behind the wheel of the car to experience the difference for yourself. The next best thing is to test the car to evaluate the difference. Anyone who has ever driven a drag-oriented car knows that the combination of tall ride height, flexible sidewall rear tires, and soft shock valving does nothing to inspire confidence in the corners. Frankly, we expected the skinny front tires to produce a skidpad number just ahead of a Conestoga wagon, but a 0.71 g is commendable. Adding the Hotchkis suspension, Flaming River steering box, and General UHP tires put the A-Body on track. More so than that was Shannon's enthusiastic response after the initial testing: "It's a completely different car now-wow!" We also have to give props to the Flaming River steering box with its much quicker ratio. Even Hudson's enthusiastic testimony and the superior test numbers don't convey just how massively different the car feels after the conversion. You just have to experience it for yourself.
SKIDPAD 600-FOOT SLALOM (G's) (AVERAGE MPH) Original 0.71 55.3 Hotchkis conversion 0.85 63.0
Alignment Specs
Hotchkis decided to dial a slightly more aggressive front alignment into the A-Body for maximum grip. While this worked well, negative camber settings of more than 1 degree will eventually generate excessive inboard tire wear. We've included a second set of street alignment settings that will still allow the front suspension to improve handling but without undue tire wear.
CAMBER CASTER TOE-IN (DEGREES) (DEGREES) (INCHES) TRACK -2.5 to -3.0 + 8 1/16 to 0 STREET -1.0 to -1.5 +6 to +7 1/16
PARTS LIST DESCRIPTION PN SOURCE PRICE Curtis Vintage 17x8 Vintage Curtis Speed $390.00 ea. Hotchkis front/rear shocks 70-56063 Hotchkis Performance 400.00 Right Stuff front disc brakes MDC66SD Right Stuff 670.00 Right Stuff rear disc brakes MDCRD01 Right Stuff 550.00 Hotchkis poly bushing 21366 Summit Racing 31.95 Hotchkis strut rod kit 14385 Summit Racing 274.95 Hotchkis steering rod kit 16385 Summit Racing 299.95 Hotchkis front upper control arm 1112 Summit Racing 599.95 Hotchkis rear leaf springs 24385 Summit Racing 349.95 Hotchkis front sway bar 22385F Summit Racing 275.95 Hotchkis rear sway bar 222385R Summit Racing 275.95 Flaming River steering box FR-1540 Summit Racing 489.95 General Exclaim UHP 245/40R17 Summit Racing 119.95 ea. General Exclaim UHP 275/40R17 Summit Racing 149.95 ea.
