Mopar Muscle Cars Handling and Performance Upgrades

The muscle cars built by Dodge and Plymouth have always had a very devoted following and a style all their own. Home to Hemis and Six Packs and clad in colors like Curious Yellow and Plum Crazy Purple, they just scream muscle car. Yet, despite competing next to Camaros and Mustangs in the old SCCA Trans-Am series, and rocking NASCAR with Hemi Chargers, Super-birds, and Daytonas, they never really caught on with the general hot rodding public as performance-handling cars. That’s a shame, because they have some real potential.

 


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Front Suspension

Mopar muscle cars have some unique front suspension features. At first glance, the suspension bears a passing resemblance to that used by Ford but there are some major differences. The most obvious is the use of torsion bars rather than coil springs. Torsion bars have been used with great success on everything from Porsches to the M1 Abrams battle tanks. The torsion bars interface with the lower suspension arms, so they are the weight bearing arms, which is the opposite of the Ford design. A wide assortment of torsion bar rates is available direct from Mopar Performance and also from companies like Firm Feel. These range from drag race (very soft) to rock-hard road race rates. Due to the mounting format of the Mopar torsion bars, they’re all adjustable for ride height, which is a feature all the other muscle car makes have to go to the aftermarket for. This makes selection much easier because ride height isn’t part of the selection process. They’re sold by bar diameter and generally .92- to 1.06-inch-diameter bars should be used for street touring to Pro Touring applications.

The iconic Mopar muscle car: rugged good looks and fast in a straight line. But cars such as this 1972 Charger can do just as well in the corners with the right parts and tuning. (Photo Courtesy Steve Rupp

The iconic Mopar muscle car: rugged good looks and fast in a straight line. But cars such as this 1972 Charger can do just as well in the corners with the right parts and tuning. (Photo Courtesy Steve Rupp

 

MFR drop spindles have larger-than-stock bearings and are available in 1.5- or 3.5-inch drop. Mounts for big modern brakes are another big plus.(Photo Courtesy Magnum Force Racing)

MFR drop spindles have larger-than-stock bearings and are available in 1.5- or 3.5-inch drop. Mounts for big modern brakes are another big plus.(Photo Courtesy Magnum Force Racing)

 

What really sets Mopar front ends apart from the crowd are their longitudinally mounted torsion bars. These are the only classic muscle cars that all have adjustable front ride height from the factory. They can also be replaced with higher-rate performance-handling bars from Mopar Performance or Firm Feel. (Photo Courtesy Ray Campbell)

What really sets Mopar front ends apart from the crowd are their longitudinally mounted torsion bars. These are the only classic muscle cars that all have adjustable front ride height from the factory. They can also be replaced with higher-rate performance-handling bars from Mopar Performance or Firm Feel. (Photo Courtesy Ray Campbell)

 

Mopars use a lower arm and strut-rod arrangement similar to many Fords. Some companies, such as RMS, offer strut rods with Heim joints on the front. Firm Feel has boxed lower arms. (Photo Courtesy Ray Campbell)

Mopars use a lower arm and strut-rod arrangement similar to many Fords. Some companies, such as RMS, offer strut rods with Heim joints on the front. Firm Feel has boxed lower arms. (Photo Courtesy Ray Campbell)

 

Heim-joint strut rods replace the high-deflection factory rubber bushing with a double shear mount and the Heim joint. This prevents unwanted caster change under braking and gives the car a tighter feel. This is a home-fabbed unit. (Photo Courtesy Justin Mancinco)

Heim-joint strut rods replace the high-deflection factory rubber bushing with a double shear mount and the Heim joint. This prevents unwanted caster change under braking and gives the car a tighter feel. This is a home-fabbed unit. (Photo Courtesy Justin Mancinco)

 

Several companies sell tubular arms for A-, B- and E-body Mopars. Most retain the factory eccentrics for adjustment. A few are single-adjustable and have to be disassembled to adjust the alignment. SPC Performance arms are double-adjustable and the lightest available with their anodized aluminum turnbuckles. Also, note the Varishock QS1 adjustable-rate shocks. There are few good performance shock choices for Mopars—these are one of them.(Photo Courtesy Team Witt Customs)

Several companies sell tubular arms for A-, B- and E-body Mopars. Most retain the factory eccentrics for adjustment. A few are single-adjustable and have to be disassembled to adjust the alignment. SPC Performance arms are double-adjustable and the lightest available with their anodized aluminum turnbuckles. Also, note the Varishock QS1 adjustable-rate shocks. There are few good performance shock choices for Mopars—these are one of them.(Photo Courtesy Team Witt Customs)


 

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These double-adjustable arms are from MFR. They incorporate Teflon-lined Heim joints and allow for increased positive caster and negative camber on stock-format front ends. (Photo Courtesy Magnum Force Racing)

These double-adjustable arms are from MFR. They incorporate Teflon-lined Heim joints and allow for increased positive caster and negative camber on stock-format front ends. (Photo Courtesy Magnum Force Racing)

 

A Sublime Green Dart, running next to a Porsche, Mitsubishi EVO, and a BMW?Yep; if it’s Justin Mancinco’s, believe it. (Photo Courtesy Justin Mancinco)

A Sublime Green Dart, running next to a Porsche, Mitsubishi EVO, and a BMW?Yep; if it’s Justin Mancinco’s, believe it. (Photo Courtesy Justin Mancinco)


 

Upper A-Arms

Tubular upper A-arms are as popular for Mopars as they are for all the other muscle cars, and for the same reasons. Properly designed upper A-arms let you crank some much-needed positive caster and negative camber into the front end, which improves road feel and performance. Fixed-length offset arms are available from Firm Feel. Single-adjustable arms are available from Reilly MotorSports and Hotchkiss among others, but they require disassembly to adjust. Double-adjustable arms with hard-anodized aluminum hex adjustment sleeves are available for B- and E-bodies from SPC. These do not need to be disassembled to adjust and have a larger range of adjustment than the aforementioned single-adjustable arms.

 

There aren’t many steering options for stock K-member Mopars. Blueprinted steering boxes with improved road feel are available from Firm Feel, but to correct or adjust bump steer, you’re pretty much on your own. These bump-steer-adjustable Heim-joint tie rods were made with parts from Coleman Machine. (Photo Courtesy Justin Mancinco)

There aren’t many steering options for stock K-member Mopars. Blueprinted steering boxes with improved road feel are available from Firm Feel, but to correct or adjust bump steer, you’re pretty much on your own. These bump-steer-adjustable Heim-joint tie rods were made with parts from Coleman Machine. (Photo Courtesy Justin Mancinco)

 

Long a favorite of Mopar drag racers, MFR offers the XRT tubular suspension conversion, which is now available in a beefed-up Pro Touring version with splined-end sway bars and optional drop spindles.

Long a favorite of Mopar drag racers, MFR offers the XRT tubular suspension conversion, which is now available in a beefed-up Pro Touring version with splined-end sway bars and optional drop spindles.

A close-up of the MFR suspension shows that it’s a radical departure from the stock format. Coil-overs replace the original torsion bars, making more room for exhaust headers. The crossmember clears even the largest stroker oil pans. Also note the rack-and-pinion steering. (Photo Courtesy Magnum Force Racing)

A close-up of the MFR suspension shows that it’s a radical departure from the stock format. Coil-overs replace the original torsion bars, making more room for exhaust headers. The crossmember clears even the largest stroker oil pans. Also note the rack-and-pinion steering. (Photo Courtesy Magnum Force Racing)

 

Higher-rate leaf springs are available from Mopar Performance and Firm Feel. But if you want to go a step further, RideTech offers an AirBar system for E- and B-body Mopars. This is not exactly a glamour shot but it shows the mounting points for the upper and lower trailing arms and Shockwaves. This package can also be ordered with coil-overs. A four-link rear suspension is also offered by RMS.(Photo Courtesy RideTech)

Higher-rate leaf springs are available from Mopar Performance and Firm Feel. But if you want to go a step further, RideTech offers an AirBar system for E- and B-body Mopars. This is not exactly a glamour shot but it shows the mounting points for the upper and lower trailing arms and Shockwaves. This package can also be ordered with coil-overs. A four-link rear suspension is also offered by RMS.(Photo Courtesy RideTech)


 

It’s also important to note that Mopar arms are particularly flimsy. They flex so much it actually affects dynamic camber and caster! That makes replacing the stock A-arms almost a requirement for good and consistent handling.

Unique Geometry

The geometry of A-, B-, and E-body Mopar front ends is much different than that of their Ford and GM counterparts. Rather than having a pronounced positive-camber curve in bump, theirs is negative. Rather than the roll center being much too low, it’s actually too high. That means they have a whole different set of issues. On paper, they should handle quite a bit better than some of the other popular muscle cars. But, in factory form, they seldom do. This is due mainly to the extremely soft torsion bar rates and shock dampening, or lack thereof, of the factory suspension components. They also used small sway bars, if they even used sway bars. Because of this, Mopars respond exceptionally well to tuning.

Body roll is inhibited by the high roll center, but the roll center is high enough so suspension jacking can be excessive. Sway bars can help with this, but combined with a high RC they can induce understeer. That makes a rear sway bar even more necessary than normal for a well-balanced handling platform. An adjustable-rate rear bar would be an exceptionally good idea. With the proper application of higher torsion bar tension and stiffer sway bar rates, along with improved dampening and alignment specifications, great gains in drivability and handling can be had. You won’t get road racing car handling from this type of combination, but you can make a very significant improvement and produce a really fun and competent street performance car.

 

Not very glamorous, but effective! Although it may look fairly stock, this 1973 440 Six Pack ’Cuda, owned by road racing great John Marconi, features 1-inch OD performance torsion bars (adjusted for a lowered stance), a 1¼-inch sway bar, and adjustable Koni Classic shocks. This simple combination yields an impressive improvement in handling and drivability on a reasonable budget.(Photo Courtesy John Marconi)

Not very glamorous, but effective! Although it may look fairly stock, this 1973 440 Six Pack ’Cuda, owned by road racing great John Marconi, features 1-inch OD performance torsion bars (adjusted for a lowered stance), a 1¼-inch sway bar, and adjustable Koni Classic shocks. This simple combination yields an impressive improvement in handling and drivability on a reasonable budget.(Photo Courtesy John Marconi)

 

This ingenious, sliding-end-link adjustable-rate sway bar was constructed by Justin Mancinco for his Dodge Dart road race car. To adjust the rate, you simply loosen the pinch bolt on the end link clamp and slide it on the bar, and then tighten it at the desired location. It’s shown at its softest setting. Also visible are the boxed lower arms, well-made homebrew Heim-joint strut rods, and functional brake ducting. These are all things that can be done by a talented enthusiast after doing the homework. (Photo Courtesy Justin Mancinco)

This ingenious, sliding-end-link adjustable-rate sway bar was constructed by Justin Mancinco for his Dodge Dart road race car. To adjust the rate, you simply loosen the pinch bolt on the end link clamp and slide it on the bar, and then tighten it at the desired location. It’s shown at its softest setting. Also visible are the boxed lower arms, well-made homebrew Heim-joint strut rods, and functional brake ducting. These are all things that can be done by a talented enthusiast after doing the homework. (Photo Courtesy Justin Mancinco)

 

Mopar sway bars are not quite as cut-and-dried as those on most other muscle cars. Many Mopars didn’t even come with factory bars, so there are no provisions to mount them. Some of the brackets I’ve seen look very flimsy. Others hang down and pose a ground clearance issue. This tubular sway bar (from Hellwig) shows sturdy, well-thought-out mounts that look like they could be factory, although they’re nicer than factory. The bar’s rates are also carefully calculated to each application. Some makers seem to think that bigger is better than just right. (Photo Courtesy Hellwig)

Mopar sway bars are not quite as cut-and-dried as those on most other muscle cars. Many Mopars didn’t even come with factory bars, so there are no provisions to mount them. Some of the brackets I’ve seen look very flimsy. Others hang down and pose a ground clearance issue. This tubular sway bar (from Hellwig) shows sturdy, well-thought-out mounts that look like they could be factory, although they’re nicer than factory. The bar’s rates are also carefully calculated to each application. Some makers seem to think that bigger is better than just right. (Photo Courtesy Hellwig)

 

Pro Touring Mopars don’t get much more serious than a Dana 60, Viper-size tires, and a fully adjustable three-link with coil-overs. (Photo Courtesy Bill Howell)

Pro Touring Mopars don’t get much more serious than a Dana 60, Viper-size tires, and a fully adjustable three-link with coil-overs. (Photo Courtesy Bill Howell)


 

The alternative to modifying the factory suspension is to go to an after-market K-frame with an all-new suspension attached. Be cautious, since some of the aftermarket K-frames maintain stock geometry and are intended only for weight reduction. These are primarily designed for and used in drag racing applications. The best known K-frame suspension conversion is the “Alter-Ktion” system from Reilly MotorSports, which has been in production for a decade. It’s proven to be simple and effective, using coil-over shocks, boasting tubular A-arms top and bottom, and bolting to unaltered frame rails. Another alternative is the “Series II” package made by XV Motorsports, which takes the curious approach of improving Mopar handling with a generous dose of factory Chevrolet parts—aluminum spindles and lower A-arms sourced from the C5 Corvette. By all indications this looks like a well-designed package because the C5 Corvette is a very well-handling car.

 

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Rear Suspension

The rear suspension on Mopar muscle cars is a pretty typical parallel-leaf-spring design. The normal technologies apply. Mopars do have a few unique features when it comes to the rear suspension, though. See Chapter 2 for more details than I cover here.

 

This 1973 440 Six Pack ’Cuda has had the rear suspension upgraded with heavy-duty rear leaf springs mounted in offset front mounts and rear shackles installed (available from Mopar performance) to make room for the pro-touring rear rubber. Rounding out the rear suspension are adjustable Koni Classic shocks and a custom adjustable rear sway bar. Combined with the well-thought-out front suspension mods shown earlier, it’s a potent performer.(Photo Courtesy John Marconi)

This 1973 440 Six Pack ’Cuda has had the rear suspension upgraded with heavy-duty rear leaf springs mounted in offset front mounts and rear shackles installed (available from Mopar performance) to make room for the pro-touring rear rubber. Rounding out the rear suspension are adjustable Koni Classic shocks and a custom adjustable rear sway bar. Combined with the well-thought-out front suspension mods shown earlier, it’s a potent performer.(Photo Courtesy John Marconi)

 

Here’s a closer look at the functional air dam and brake cooling ducts on Justin’s car. Cold air is the secret to keeping the modest Cordoba disc brakes cool enough to work lap after lap. (Photo Courtesy Justin Mancinco)

Here’s a closer look at the functional air dam and brake cooling ducts on Justin’s car. Cold air is the secret to keeping the modest Cordoba disc brakes cool enough to work lap after lap. (Photo Courtesy Justin Mancinco)


 

Unique Springs

First are the legendary “Super Stock” springs. These were designed by Chrysler specifically for drag racing. They feature more forward leaf bias than typical springs would, to provide better traction. It’s not unusual to see them being run with spring clamps on the front half of the leaf pack and no clamps on the rear half. As discussed previously, this is not ideal for handling. It decouples the rest of the spring pack from the main leaf in droop, or for the inboard spring in roll while cornering. This decoupling adversely affects cornering and braking, so make sure there are clamps on both ends of the spring packs for all-around performance use. The forward leaf bias isn’t a bad thing, as long as the springs provide enough roll rate for a handling application and otherwise fit into the total package.

Mopar Performance offers a kit to move the leaf springs inboard for more tire clearance. This is fine, but be aware that this adversely affects the spring’s motion ratio in roll, so more spring rate (or sway bar roll rate) may be necessary than would otherwise be required.

 

These down bars are tied into the chassis exceptionally well, reinforcing the front end on a 1969 Hemi Road Runner with an MFR tubular front suspension package. These bars go from the cowl to the shock towers, and then to the end of the unibody. They even have integrated mounts for a bushing-equipped motor plate for even more rigidity. This represents good thinking on a unibody car with monster torque. (Photo Courtesy Magnum Force Racing)

These down bars are tied into the chassis exceptionally well, reinforcing the front end on a 1969 Hemi Road Runner with an MFR tubular front suspension package. These bars go from the cowl to the shock towers, and then to the end of the unibody. They even have integrated mounts for a bushing-equipped motor plate for even more rigidity. This represents good thinking on a unibody car with monster torque. (Photo Courtesy Magnum Force Racing)


 

An unusual Mopar rear suspension option is the use of a tall, adjustable pinion snubber to enhance traction. This, in effect, uses the pinion housing of the rear end like an ultra-short torque arm or slapper bar. It’s actually pretty effective, as many Mopar racers have proven over the years. It should be used with caution, though; by design, snubbers add binding and effective spring rate. A pinion snubber has much less affect on roll than a comparable bolt-on slapper bar arrangement. But it can still have an unsettling effect if and when it makes contact in mid turn and increases the effective spring rate of the rear suspension. So take advantage of an adjustable pinion snubber at the drags, and then adjust it down and out of the way for street driving and any type of handling use.

Spring Replacement

Another cool feature of Mopar leaf springs is how their front mount can be replaced with a heavier-duty reinforced mount, a mount that allows for specific aftermarket shorter springs, or even mounts with more than one mounting hole. This last option allows you to adjust the side-view geometry of the springs by raising the front of the spring. Doing so lowers the car roughly 1 inch, and also improves off-the-line traction.

Like many other popular muscle-car platforms, rear suspension packages are available to replace the leaf springs with links and coil-overs or air bags. Some of the most popular are the RideTech AirBar and Chassisworks G-Bar, which are related systems, and the Street Lynx from RMS. These are converging four-link systems.

Sway Bars

Mopar sway bars are also a little different than those of other muscle cars. For starters, a lot of Mopars didn’t come with sway bars from the factory. This fact contributes to the reason they’re not often associated with performance handling. Secondly, those cars not equipped with sway bars don’t have any provisions to mount them! Naturally, the aftermarket has stepped in and made bars and brackets available, but they vary wildly in how well they’re executed. Some of the brackets for the front sway bars appear to be cheaply made. Look for beefy, clean brackets and bars that don’t compromise ground or tire clearance.

 

If you can tear your eyes away from the dual-quad Hemi, notice the tubular reinforcing bars running from the top of the cowl to the shock towers and the front of the K-member. These “down bars” are part of MFR’s reinforcing package for high-horsepower and Pro Touring Mopars running the XRT tubular suspension package. These down bars really tie the front end together and add a huge amount of torsional stiffness. Tying the shock/coil-over mounts more completely into the rest of the car’s structure is also a great idea. (Photo Courtesy Magnum Force Racing)

If you can tear your eyes away from the dual-quad Hemi, notice the tubular reinforcing bars running from the top of the cowl to the shock towers and the front of the K-member. These “down bars” are part of MFR’s reinforcing package for high-horsepower and Pro Touring Mopars running the XRT tubular suspension package. These down bars really tie the front end together and add a huge amount of torsional stiffness. Tying the shock/coil-over mounts more completely into the rest of the car’s structure is also a great idea. (Photo Courtesy Magnum Force Racing)


 

Mopar rear sway bars are typically frame-mounted. That’s a good thing because it makes the weight of the bar sprung weight, rather than unsprung weight. However, some very good Mopar bars are axle-mounted instead to gain more bar-to-tailpipe clearance, extra room for adjustable end links, and multiple mounting points for rate adjustment. Many of the newer rear bars weigh only 8 or 9 pounds, and, because they’re being bolted to a 300-pound rear axle, I’m not concerned about where they’re mounted, just that they work as promised. Of course, I prefer an adjustable-rate bar every time it’s available.

Flex Reduction

The lack of chassis stiffness reappears again in Mopar muscle cars. Subframe connectors are a must, and are available from Mopar Performance, Hotchkis and others.

 

With tasteful 18-inch-diameter billet-aluminum “Magnum 500” wheels and original-style paint and graphics, this Super Bee pulls off the classic muscle-car look perfectly. The MFR tubular suspension and modern brakes make it perform equal to modern cars in more than just a straight line.

With tasteful 18-inch-diameter billet-aluminum “Magnum 500” wheels and original-style paint and graphics, this Super Bee pulls off the classic muscle-car look perfectly. The MFR tubular suspension and modern brakes make it perform equal to modern cars in more than just a straight line.


 

Building a Pro Touring-style Mopar may be taking the road less traveled, but that’s often the most rewarding road.

 

Written by Mark Savitske and Posted with Permission of CarTechBooks

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