In this chapter I discuss several specific types of GM muscle cars and go over some strong and weak points of each design. I also cover some aftermarket parts and how they work in various applications. Each section builds upon the last, so read all of the sections even if you don’t have one of those cars. You may accidentally learn something cool!
This Tech Tip is From the Full Book, HOW TO MAKE YOUR MUSCLE CAR HANDLE. For a comprehensive guide on this entire subject you can visit this link:
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Probably the most produced of all the muscle cars, the GM A-bodies were made by every GM brand except Cadillac and GMC. They were good sellers too. Pontiac’s LeMans/Tempest/GTO, Chevrolet’s Chevelle/Malibu/Super Sport, Buick’s Skylark/Gran Sport (GS), and Oldsmobile’s Cutlass/442 are still surprisingly plentiful. Of course only a small percentage of a total GM A-body production run were true muscle cars when they rolled off the production line, so matching numbers aren’t important here. As far as I’m concerned, a Chevelle that started off with a 307 and Powerglide but now runs modern suspension, brakes, 5-speed manual transmission, and 600 hp is much more of a muscle car than a 325-hp 396-ci Chevelle SS ever was! Heck, in my opinion, a four-door station wagon with those performance mods is a muscle car too (and they are out there).
These cars are split into four generations: the first from 1964 to 1967, the second from 1968 to 1972, the third from 1973 to 1977, and the fourth from 1978 to 1980. This last generation is kind of the black sheep of the A-body clan; in 1981 they were reclassified as G-bodies and continued under that moniker until 1988.
The GM family tree has many branches. The 1973 to 1977 A-bodies used the front suspension from the 1970 to 1981 F-bodies, which later went on to be used on the 1978 to 1996 GM B-bodies, which included the Chevy Impala/Caprice, Buick Roadmaster, and others you may not expect (like two-wheel-drive Chevy Astro vans). The rear suspension of those cars was basically 1973 to 1977 A-body as well. The G-body front end was used for the two-wheel-drive S-10 pickups and was still manufactured until 2005 with very few changes.
The geometry of the 1964 to 1972 models is almost identical, and basically very bad. The 1973 to 1977 models are not bad. The 1978 to 1980 (and by extension, the 1981 to 1988 G-body) are actually slightly worse than the 1964 to 1972 A-bodies. The only reason they generally drive a little better is the improved tuning (sway bars, spring rates, shocks, and tire technology).
GM A-Body 1964 to 1972
With the 1964 to 1972 A-bodies, the first concern is their front end and steering geometry. It’s just plain lousy. It’s actually backward in pretty much every way that it can be. They have pronounced positive camber gain in bump, a subterranean roll center that’s very unstable, and a healthy dose of bump steer. As far as I’m concerned, doing anything to this chassis without fixing these issues is like putting lipstick on a pig.
To correct these issues, you need to target the problem areas and tweak them into shape. Because they’re geometry problems, you need to move the suspension’s pickup points to get the job done. In this case, the pickup points of the upper ball joints need to go up, a lot. Raise them until they’re traveling in an inward arc as soon as the suspension starts to compress. That helps give you proper negative camber gain. The most popular ways to do this are by adding taller spindles or taller ball joints.
Tall Spindle Swaps: Tall spindle swaps date back to the 1980s, with outfits like HO Racing using B-body spindles with B-body lower ball joints that were machined down to fit the A-body’s lower A-arms. Second-generation (1970 to 1981) GM F-body spindles and ball joints also work. Getting a decent alignment out of these early packages was always a real challenge (even with offset cross shafts) and in some cases it was impossible. The additional height and more-aggressive ball-joint axis inclination made the stock upper A-arms poorly suited for use with these spindles. Even on a good day, alignment options were severely limited. The situation improved when companies started making application-specific tubular upper A-arms (for this swap) that were shorter, and had more offset toward the firewall. These helped make it a much more usable package. Unfortunately, it still doesn’t alleviate the many downsides to this swap.
The fact is these spindles were designed for a totally different car, and as a result you find a lot of issues. For example, the steering arms put the tie rod ends in the wrong location. The A-body starts out with massive bump steer (about 1.5 inches of total toe change over 6 inches of suspension travel) due mainly to a vertical misalignment of the outer tie rod ends. The B-body arms roughly double that misalignment and the resulting bump steer. The only factory cars I’ve ever analyzed that were worse than this were a few Chrysler products from the mid 1940s. This is just completely unacceptable in my book—you’re trying to make your car handle, steer, and stop better; not worse.
There’s more too; the steering arms are also about 1 inch longer. This slows down the final steering ratio, making the turning radius much larger. You can forget about doing U-turns in a reasonable arc, and the fast-ratio steering box you just spent good money on is now a not-so-fast ratio. The Ackerman error is also made worse, which makes for a lazier turn-in when cornering and more tire squeal when parking. This swap is often sold as part of a package with giant sway bars to inhibit individual wheel movement and reduce the amount of perceived bump steer, but that doesn’t fix the problem; it just masks it a little. In other words, if the steering does bad things when the suspension moves, then don’t let it move much.
But wait; that’s not all! The B-body spindles are also massively heavy when compared to the stock parts they replace. Their non-modular format is hard to adapt properly to modern brakes, and they increase the track width of the car by 3/8 inch, which can cause tire/fender clearance issues. They improve the suspension geometry markedly, but it’s at the cost of reduced performance everywhere else. This swap was a good first attempt, and at least proved that these cars could be made to handle. But the industry has made huge strides in the past 20 years and this concept’s time has come and gone.
Aftermarket Tall Spindles: Modern after-market tall spindles are designed to be a direct fit to the A-body platform and eliminate the pitfalls of the B-body spindle swap. For the most part, they do that pretty well. There are several varieties, and they’re not all created equally. First, they vary in height. Most are about 1.5 inches taller than stock, but some (like the Fat Man Fabrication spindle, for example) are about 1.75 inches taller. That may be a good thing on a car that isn’t lowered with springs, but it can be too much of a good thing on one that is.
Some of these tall spindles also feature relocated steering arm mount holes to improve (or at least change) bump steer. The Heidt’s product leaves them alone. This might be a good choice if you’re running a rack-and-pinion steering system that corrects the bump steer on the inboard side, such as the product offered by Unisteer. They are a “no harm—no foul” upgrade with stock steering.
Other manufacturers relocated the steering arms to a lower position for improved bump steer on 1967 to 1969 Camaro (first-generation F-body) applications. This is a good thing on a Camaro, but while they share the same stock spindles with 1965 to 1972 A-bodies (1964 is slightly different), they have a totally different steering design with opposite requirements for bump steer correction. That means that they roughly double the bump steer issue on an A-body. At least the steering arms are still stock length, so it avoids the steering-ratio and turning-radius issues of the B-body spindle swap. Even the outstanding American Touring Specialties (ATS) AFX tall forged-aluminum spindles have steering arm holes in this first-generation F-body optimized location. But ATS includes an A-body-specific set of aluminum steering arms, which I co-designed with them to correct the bump steer on the A-body platform.
Some other manufacturers have taken a much different engineering approach and have cunningly ignored the problem. As the saying goes, let the buyer beware! Check for yourself; take a gander at your stock spindle and notice where the steering arm mount holes are located (vertically, in relation to the bottom of the spindle). If you’re looking at A-body spindles where the steering arm holes are about 1/2 inch lower than stock, and they don’t come with new vertically offset steering arms, then you’ve got a serious bump steer issue. Keep looking elsewhere. The experts at Detroit Speed and Engineering (DSE) have bucked the “holes-in-the-wrong-place trend” and have relocated the holes upward on their A-body-specific spindles to achieve proper bump steer correction for the A-body platform.
A common theme with all of these aftermarket tall-spindle upgrades is that they have additional drop built into them. Most have 2 inches of drop when compared to stock. The ATS AFX aluminum spindles have 7/8 inch. This additional drop can be good or bad, depending on your total package. Two inches of drop teamed with an air suspension can let you run more air pressure (and therefore more spring rate) at a given ride height—a good thing. On cars running coil-over conversions, a 2-inch-drop spindle allows you to achieve lower ride heights with less lower A-arm bump travel. This gives a larger vertical envelope in which to stuff the coil-over shocks, so a longer coil-over and longer springs can be employed. Again, that’s generally a good thing.
With conventional performance coil springs, 2-inch-drop spindles can start to cause some problems. Almost all the performance coil springs offered for these cars are also designed to lower the car’s ride height. Dropping the suspension some, with custom springs, does put the lower A-arms in a more favorable orientation for good geometry than stock. But adding 1 to 2 inches of spring drop to a car with 2-inch-drop spindles often leads to the headers and/or oil pan being introduced to the pavement. Since hitting the ground isn’t good for performance, that’s less than ideal. Only one manufacturer I know of (DSE) offers a set of performance-rate stock-height springs.
There are also some wheel and tire clearance issues with 2-inch-drop spindles. Since the spindle pin has been raised 2 inches, but the steering arms and tie rod ends haven’t moved, you’ve in effect moved them 2 inches closer to the inner lip of the wheels and the tire sidewalls. That may force you to run smaller wheels and tires than you otherwise could. Spindles that relocate the steering arms downward make this clearance issue even worse, and those that relocate them upward somewhat reduce it.
There’s also a more subtle effect of spindle drop on the A-body front end: a reduction in lateral roll center migration. Depending on how the geometry has been otherwise modified, this effect seems to peak right around 1 inch of drop; then it trails off again. That’s the reason for the 7/8 inch of drop engineered into the AFX spindles. Because most A-body performance lowering springs are 1 to 1.2 inches or so, you end up with about 2 inches of total front drop. This makes for a very nice, lowered (but still fully functional) ride height.
So, what about 2-inch-drop spindles that aren’t taller than stock? Do they move the critical pickup points to improve the geometry? No. Do they do anything to improve the steering geometry? No. Do they cause more wheel/tire clearance issues? Yes. Do they make it harder to use performance-bred lowering springs and still have a usable ride height? Yes. Well, three strikes and you’re out…and they got four. Make it five, because you already have stock spindles, and you have to pay for these 2-inch-drop spindles. Again, do the homework first, and know what you’re getting before laying out your hard-earned money.
Most tall spindles for GM A-bodies are the same general configuration as stock, in that they use the same iron construction and accept stock wheel hubs. The only one currently on the market that really bucks this trend is the American Touring Specialties (ATS) AFX tall forged-aluminum spindle. The first thing that catches your eye is that they’re made of forged 6061 T6 aluminum. Their overall look is much beefier than the stock spindles for strength, but the aluminum alloy keeps them light. The second thing you notice is that they have modern C5 Corvette hub/wheel bearing packs and late-model GM-style brake brackets forged right into the spindles. This combination delivers wheel bearings designed for serious cornering on modern tires and the ability to easily mount Corvette or any modern-format performance brakes to the spindles.
Generally, those brake packages are less costly than their stock spindle equivalents, which does help offset the higher cost of the spindles. When properly complemented with the right A-arms, springs, and alignment specifications, these spindles yield geometry rivaling modern performance cars and easily beat out many aftermarket chassis. If you have the budget, I highly recommend them. They also sparked interest in a market that I don’t think anyone but their designer (Tyler Beauregard) knew existed. Hopefully, in the near future you’ll see a lot more modern-format aluminum spindles like these hit the market. Some will probably go to billet construction and I’m sure at least one company will do a cheap overseas-made version. It’s almost inevitable that someone will make them, but you don’t have to buy them.
Aftermarket Tall Ball Joints: The other geometry correction method is based on using taller-than-stock ball joints. Circle track and road race teams have been using non-stock ball joints for years to make small changes in geometry, but since they were typically sourced from trucks, the mounting format is usually different than stock; often the tapers are different, too. This is not a big deal if you have a well-outfitted race shop, but the gains are still very modest. Some race cars use monoballs (spherical bearings) with ball-joint studs through them to tweak geometry, but they don’t hold up very well on the street (especially the lowers) and they only have half the angular travel of a factory ball joint. They only really work on cars set up race-car stiff.
Then, Howe Racing Enterprises designed the “Precision Series” modular CNC-machined ball joints. I remember seeing an ad for them in a magazine for the first time, and it hit me like a ton of bricks. I realized that I could fix flawed suspension geometry with these things and retain the stock spindles. I couldn’t wait to get my hands on some of these new components. The rest is history.
Since then, I’ve put together nearly a dozen tall ball-joint packages (sold as Savitske Classic & Custom StreetComp packages) for various cars. The most popular is for the GM A-body. The trick to working with these components is attention to detail. Because they’re modular, there are thousands of possible combinations and only one is ideal for a given vehicle and package.
Despite having so many options to choose from, I ended up working with Howe engineers to design several application-specific ball-joint components as well. All are CNC-machined, heat-treated steel with different coatings for each specific component. The resulting products are, in my opinion, the best of ball joints. They are super strong, super smooth, adjustable for wear/lash, and rebuildable. Since the outboard suspension pickup points are the ball joints, they’re a very efficient way to tweak the geometry.
The Stage 2-Plus package rivals the geometry of a 2002 GM F-body, which is not bad for a simple bolt-on kit! This package uses the ball joints in non-stock heights to duplicate the improved geometry of a good, tall spindle with about 3/4 inch of drop. We also built in a roughly 80-percent-overall improvement in bump steer. I’m sure this idea will eventually catch on with other companies, but it’s gratifying to know we at Savitske Classic & Custom (SC&C) were the first to really run with it and perfect it.
By the way, don’t bother contacting Howe about using them for a street-based car. They do circle track race cars only. I mention them by name just to give them full credit for producing a great product.
Tubular A-Arms: All of the technical information I discussed in Chapter 4 also applies here. If you alter the geometry in a meaningful way, the stock upper A-arms need to go in favor of a set that was designed to complement the new geometry. The lowers can be retained if they’re in perfect shape with no cracks, dents, or rust, and if you’re only building a mild street-application car. Otherwise, I would rather see them replaced with some new tubular arms that are stronger, more rigid, and haven’t already gone through countless fatigue cycles.
There are lots of lower A-arms on the market for the GM A-body, so look them over closely before you buy. Most are tubular replacements for the stock arms, but stronger, and often with better bushings. There’s nothing wrong with them but I always felt that format could be improved upon.
Luckily, so did SPC Performance, and the result is a new lower A-arm with some very cool features. I admit I had a hand in designing these arms, so I may be biased, but the features are undeniable. The first is a modular lower spring pocket, allowing the use of conventional coil springs, coil-over shocks, or Shock-wave air springs. This modular pocket allows some extra room for the latter two for more bump travel. With conventional coils, the SPC spring shim kits allow you to change the ride height of the car without changing the springs.
The total adjustment range available is a massive 33⁄4 inches. That’s 2 inches of drop to 13⁄4 inches of lift. To change ride height, you just add or subtract spring shims with a 2:1 ratio. For instance, a 1/4-inch shim equals 1/2 inch of ride height change. There’s no guesswork. Greaseable Delrin bushings and provisions for modern progressive-rate jounce bumpers are also offered by SPC. Finally, they have modified geometry that re-centers the wheels within the wheel wells after you’ve added a bunch of positive caster. This feature can be a big help on lowered cars with big tires up front.
Springs and Shocks: Traditional coil springs, coil-over shock setups, or air springs—they can all work well, so it’s pretty much up to you. Conventional coil springs are the easiest to set up, the most durable, and by far the most foolproof.
In the A-body, coil-over shocks generally work better in the rear than in the front simply because there’s more room for a longer coil-over and room to swing the spanner wrench for ride height adjustment. It’s also harder to mess up the tuning (not impossible, just harder). Several companies offer bolt-in coil-over shock rear suspension conversions. It’s perfectly acceptable to run conventional performance coil springs and adjustable shocks in the front and the same brand of adjustable coil-overs in the rear. I often have clients do this with SPC Performance adjustable-height lower A-arms up front. That gives them a bulletproof system that’s easy to tune on both ends.
Four-Link Rear Suspension Issues: The A-body four-link rear suspension has some inherent binding issues, so try to minimize them with the correct-format control arms. With rear suspension arms, you want something with greaseable flex joints or at least a swivel in the middle of the arms to allow torsional freedom of movement. The roll center is very high, so run modest spring rates and tune with a rear sway bar. Note that as you lower the rear of a GM A-body, the rear roll center goes up. That’s one good reason not to lower the rear of an A-body any more than you have to. If you insist on lowering it more than an inch or so, consider one of two alternatives.
First, run large-diameter rear wheels and tall tires that fill out the wheelwells and give the car a lowered look, without being slammed. Second, add a frame-mounted Watts link, such as the one I co-designed with Fays2. The Watts link is something you may want to consider even if you haven’t lowered the car too much. The Watts link does an outstanding job of affixing the roll center, and since this is a frame-mounted Watts, it also couples it to the CG.
There’s also nothing better for lateral axle location. The Watts link makes the normally skittish, converging four-link factory suspension suddenly very linear, predictable, and precise. Remember to use rubber bushings in the axle “ears” to allow compliance in the upper trailing arms. This lets the Watts link do its job unhindered.
This package also allows you to lower the roll center a bit. Don’t get carried away, for best performance you want to keep the new roll center within the range it originally migrated in. Basically, this means don’t lower it more than 2 to 3 inches from stock. If you decide to lower it, expect to add more rear sway bar and or spring rate to keep the car balanced. If you run a Watts link, do you need to run a rear sway bar? Yes. They perform completely different functions and actually complement each other very well.
Sway Bars: The front sway bar choice varies with your desired level of performance and the overall package. Older designs tend to be one-size-fits-all, and can have fitment issues with larger tires and/or wheels with greater-than-stock backspacing. Some savvy companies have started building application-specific bars with better-than-stock clearance, such as the products offered by Hellwig, DSE, and RideTech. Tubular bars don’t work any better than solid units, but they’re a lot lighter. The racy splined-end bars don’t work any better than bent tubular bars or solid bars; they just look neater.
In the rear, conventionally mounted (to the lower trailing arms) bars are largely ineffective and cause binding in the arms. A 1-inch-diameter rear bar bolted to the lower control arms is better than nothing, but not by much. You want a link-mounted bar with links running all the way to the frame or crossmember. This is how bars are mounted on 99 percent of the cars in the world and it is the correct way to go about it.
Many of these have adjustable rates, which is great! It lets you tune the car to your combination and driving style. It’s best to always start out at the softest rate (the one farthest from the transverse torsion bar part of the bar) and tune from there.
GM A-Body 1973 to 1977
Owners of these cars have had it rough. Engine horsepower was down, and size and weight were up. The government-led, 5-mph battering-ram bumpers became mandatory and the A-body became more of a luxury cruiser than a muscle car. That is not to say that they didn’t build some cool cars, though—the Pontiac GTO and CanAm, Chevy’s Laguna S3, and the Hurst/Olds 442 were all great machines. What’s forgotten is how these cars actually had the best suspension of any of the A-bodies! Their front end and geometry was inherited from the 1970 to 1981 F-body, and those cars handled pretty well. They also have very respectable bump steer curves. The camber curves aren’t great, but they’re not backward either! The rear suspension is also slightly better, with longer trailing arms and less acute convergence angles.
These cars don’t need a tall spindle swap; they already have them. They can use a little help making the geometry more aggressive, and for that SC&C makes a Stage 1 package, with slightly taller upper ball joints. They can benefit from more rigid suspension arms and a good performance alignment as well. All the normal rules apply with regard to spring rates, shocks, and sway bars for tuning. These cars were set up very soft and plush from the factory, so a little tuning can really make a dramatic difference. The only thing really missing for these cars is a link-mounted rear sway bar, and by the time this book is in print, Hellwig should have an adjustable-rate tubular unit in production.
Note: The above information about the 1973 to 1977 A-bodies also applies to 1978 to 1996 B-body Impalas, Caprices, Roadmasters, and the like. They are all, for most intents and purposes, the same chassis. You wouldn’t think you could get much handling performance out of a car the size of a whale, but I have clients regularly challenging C5/C6 Corvettes and Vipers at autocross events and still driving them to work a couple of days a week. Amazing!
GM A-Body 1978 to 1980
Most people refer to these cars as G-bodies because this platform was renamed G-body in 1981. Any information that applies to G-body cars applies to these as well.
GM G-Body 1981 to 1988
I was going to give these cars a section of their own, but they really don’t need it. All of the information pertaining to the 1964 to 1972 A-bodies can be applied to the G-body platform, with one exception. At the time I’m writing this, there is only one aftermarket tall spindle option: the American Touring Specialties (ATS) AFX aluminum spindles. Thank-fully, it is a great option. We did even more work on this one and incorporated some steering geometry tweaks from the older C5 Corvette spindle conversion package. That setup was very effective, but also expensive to build and was limited to pretty low ride heights.
The SC-AFX package is less expensive and more versatile. The steering modifications fix the factory steering Ackerman issues and also slightly quicken the steering ratio. The response and turn-in are incredible. The G-body platform is typically lighter than the older A-body cars and much lighter than modern cars in the same class, so performance can be fantastic.
One inherent G-body problem is that it’s not a very rigid platform. GM put them on a diet and started by removing the forward and aft chassis crossmembers. They also cut away most of the cowl structure, the steel dash structure, and much of the rear seat bracing to save weight. Some models had various conduit-like tubular braces here and there, which were better than nothing, but still far from ideal. The T-top cars are especially flexible because they lack some of the torsional rigidity of a full roof. For this reason, I designed the SC&C HD Chassis brace for G-bodies. It ties the front frame rails together and adds triangulation to the front end.
To give you some idea of how flexible these cars are, the brace only fits if it’s installed with the weight of the car sitting on its wheels. Boxing the center span of the frame rails and/or adding firmer body bushings is also a good idea. Be sure to at least replace the radiator support bushings; they’re especially soft and allow far too much movement. Bracing up the chassis also keeps your body panel gaps consistent.
The limited-production Buick GNX torque arm/Panhard bar setup is not a particularly well-designed suspension and should be avoided. The torque arm is too short and in a compromised location due to packaging limits. The Panhard bar is too short and not level at factory ride height. You are better off tweaking the factory converging four-link. It’s a shame the GM engineers didn’t spend the same time and effort on overhauling the front suspension instead.
GM First-Generation F-Body
These are arguably the cars that started the “performance handling for muscle cars craze.” The 1967 to 1969 Chevy Camaro and Pontiac Firebird are undeniable classics and make great performance platforms, once you change the suspension all around so it works properly. First-generation cars suffer from the same abysmal suspension geometry as the early A-bodies and have similarly poor bump steer curves as well. The solutions to these issues are where they differ some.
Tall Spindles and Ball Joints
There is a plethora of tall spindle options for the first gens; in fact most of the A-body tall spindle modifications started here. In this case, the steering arm mounting holes issue is less of a concern. Those with relocated steering arm mount holes were almost all designed with the first gens in mind, so you’re generally good to go. The cautions about wheel/tie rod end clearance issues with 2-inch-drop spindles apply even more to this platform. The steering arms are bent down much closer to the wheel/tie rod ends than on the A-body to begin with, and the bump steer solution moves the tie rod ends down even farther still. If you run a 2-inch-dropped tall spindle on these cars, measure very carefully for your wheels before you buy them. Similarly, if you already have the wheels you want to run, measure very carefully to see if you’ll still have enough clearance when you lose 2 inches of it.
A tall-ball-joint package is also available from SC&C for the first-gen F-bodies, but it differs from the A-body package in that it retains the stock lower ball joints and instead includes tall tie rod ends for bump steer correction.
There’s still another option for first gens that doesn’t exist for other GM cars called the Guldstrand mod. Named after legendary racer Dick Guldstrand, who pioneered it, this modification relocates the cross shafts of the upper control arms down and toward the firewall to move the inner pickup points for improved geometry and for more positive caster. This was first done in the SCCA Trans Am racing series to basically cheat. They would cut the factory welds securing the upper A-arm mounting brackets to the subframe, section them, and then re-weld them back on, closer to the firewall. Done correctly, it was very hard to tell they had been tampered with. In the modern version (with no SCCA tech officials to scrutinize) folks simply re-drill the cross shaft mounting holes. There were many different versions of this modification back in the 1970s, and there are still more today. Everybody seems to have their own version, even me.
So, is this the answer to all your hopes and dreams—a cheap fix that turns your car into a road racing machine? Well, not really. It is a step in the right direction, but it has issues too. When you re-drill the holes, the top of the perch hits the inside of the factory A-arms and has to be modified for clearance without weakening it too much. The more you lower the cross shafts, the closer they get to the subframe, and the less droop travel you have. Since droop travel can improve ride quality without adversely affecting handling, that’s a bummer. The post-mod geometry is better than stock, but still not great by any modern yardstick. Finally, it makes it even more challenging to get a good performance alignment. The relocated perches worked better in this regard, but not everyone wants to cut up their classic car. Once you cut stuff off, it’s hard to put it back again.
Because these cars have removable front subframes, they also have another option. It’s possible to swap out the whole thing for an aftermarket one. They range from the SpeedTech unit that uses almost all stock-configuration aftermarket components (except for rack-and-pinion steering) to designs from Art Morrison and DSE that make use of C6 Corvette spindles and some other upgraded components.
Generally, these subframes use either coil-over or Shockwave air springs and they’re usually easier to work with on these dedicated subframes than they are when used as a conversion on a factory subframe. All the aftermarket subframes I’m aware of use rack-and-pinion steering. That’s usually viewed as a good thing. They also typically allow for somewhat wider front tires, because some extra clearance was freed up by using the rack-and-pinion and moving the sub-frame rails inboard. The extra clearance could also have been gained because the rack-and-pinion used in the package has a larger turning radius and, therefore, more clearance because the wheels don’t turn as far. Watch out for that one!
The Chassisworks G-Street subframe has a wide array of options from mild to wild. Everything from the hardware to the sway bars and A-arms can be upgraded. It’s a competent performer in any of its guises and can be configured to do anything you want, from shiny show car to road racing.
Rear Suspension Options
The rear suspension of the first gen is another area that can use some improvement. The old parallel-leaf-spring Hotchkis-drive format has some issues, as I discussed earlier, but it can still be made to function very well. A good set of performance leaf springs, an adjustable rear sway bar, and a Watts link can take the old parallel-leaf-spring design to a whole new level of handling.(See the sections on leaf-spring tuning and augmentation in Chapter 2 for more details.)
The other option is to upgrade to one of the many aftermarket link-type rear suspension systems available. These range from direct bolt-in kits (like Chassisworks’ G-Bar) to more involved weld-in systems that require modifications to the floor and/or unibody (like DSE’s Quadra-link). Most of these systems are four-link designs, but there are some exceptions here as well. The Lateral Dynamics–sourced three-link/Watts link and SpeedTech’s torque-arm system are good examples.
Each of these designs has its strengths and weaknesses. Some have very little adjustment and may be best for those who aren’t well versed in how the suspension works. Those will, how-ever, be more limited in how many things they can do well. I am a big fan of the more-adjustable systems with adapt-able geometry, because no two cars and clients are exactly alike.
I’d rather spend time consulting and dial the car in exactly to the client’s needs than to accept the tradeoffs of a one-size- fits-all package. The higher the power level of the car, the more adjustability comes into play. A 400-hp car hooks up with just about any suspension, as long as it has decent tires. A 650-hp car is a whole different story, and requires a suspension with enough anti-squat to help plant the tires. It also requires very beefy components and low-deflection pivot points to maintain good control.
In general, and this is by no means an all-inclusive list, systems like the Chassisworks G-Bar, SpeedTech Torque Arm, and DSE Quadralink are excellent choices for a high-performance street car, with crisp handling and great ride characteristics. They would also be great choices for casual autocross use. They work best in a narrow range of ride heights and don’t have a lot of geometry adjustment. So if you’re planning on doing a lot of drag racing or running the car with a higher or lower stance than the manufacturer recommends, they may not be ideal choices.
For putting big power down, the adjustability of the Chassisworks G-Link system is hard to beat. It has enough adjustment built into the system that it can be optimized for everything from street performance to autocross and road race duties to drag racing without replacing any parts. Other high-end systems may surpass the G-Link slightly in one department or another, but the G-Link is the best multitask design I’ve seen. It uses really beefy components and bulletproof Delrin race, greaseable pivot balls at all eight suspension pickup points. It can be configured to work well at a variety of ride heights. This system offers two choices for rear sway bars: an axle-mounted tubular bar or a frame-mounted adjustable-rate solid bar. Note that some of the other systems do not have a sway bar available, which limits tuning options.
Both the front subframe and link rear suspension conversion markets are flooded with offerings, and I’ve missed a lot of them here. Some that I’ve not mentioned are admittedly good ones, but using the technology from earlier in the book and studying the few examples I’ve referenced here should help you apply that knowledge to any other system you see. This certainly can help determine if it’s going to work well for you and your car.
Almost all of these rear systems are designed to work in mini-tubbed applications as well as in cars with stock wheel wells. Some offer a mini-tub-specific version, so be sure to order the right one for your application.
Should you mini-tub your car? Bigger tires generally equate to more traction, with all else being equal. Improved traction means putting more power to the road, which is the goal here. At the end of the day, it’s probably as much about getting the right look as anything else, but this is a cosmetic option that also adds performance. If it’s in the budget and you like the look of a mini-tubbed car, go for it. If not, spend more time researching good tires, especially R-compound tires, and you can still get awesome performance out of your car.
Whatever suspension package you decide on, don’t forget you need a rigid chassis to let all of those cool parts do their job efficiently. Subframe connectors are a must-have, and harder-than-stock or even solid body-mount bushings are a good idea as well.
GM Second-Generation F-Body
It’s good to see second-generation (1970 to 1981) GM F-bodies starting to soar in popularity. I’ve always thought they were great-looking cars and they’re a really good performance-handling platform. The front suspension, designed by Herb Adams, is competent even by modern standards. The advantage of running a geometry improvement package (such as an SC&C Stage 1 setup) is that its dynamic geometry allows you to get the same handling with street alignment specs where you’d normally have to run race alignment specs. In doing so, you can have great handling, good tire wear, and excellent street manners too.
An intermediate option is a Speedtech Street Fighter package, featuring AFX 2.0 spindles, tubular A-arms, a weld-in long-travel coil-over conversion, and revised steering. It splits the difference between mild bolt-ons and a full aftermarket subframe.
The final level is an aftermarket sub-frame offered by Chassisworks, DSE, and many others manufacturers. These run the gamut from excellent to no better than stock so do your homework before you buy!
The rear leaf-spring suspension responds to all the same modifications and aftermarket link-type rear suspension packages as the first-generation F-body, so I won’t rehash it all here. The selection of packages isn’t as large for the second-generation cars, but most of the best players are well represented.
The biggest design flaw with the second gen is chassis rigidity, and it seems particularly noticeable on the later, heavier second gens. If your car doesn’t have subframe connectors in it, don’t even think about building the car without them. Again, harder-than-stock or solid subframe bushings are a very good thing to consider as well. There are also some underhood structure kits, pioneered by Herb Adams/VSE. These are another great idea. If you own a second-gen F-body and you’re disappointed that this section is as short as it is, don’t be. It means you chose a good performance-handling platform to start with.
GM Third-Generation F-Body
Honestly, I wasn’t going to include these cars in the book. The performance versions (such as the IROC Camaros and WS6 Trans Ams) are already very competent handling cars, even by modern standards. Also, to me, these aren’t old muscle cars. Of course anything with a third brake light is a newer car to me.
Chassis rigidity is still a big issue with these cars, and as always the T-top cars are worse than the hardtops. There’s no need for different subframe bushings here, since these cars don’t have any. But subframe connectors are still very important. Because they have strut-type front ends, they also pass dampening loads (they still use conventional springs) into the strut towers, so a strut tower brace is a good idea. If you can use it as part of a bolster to triangulate the front end structure, it’s even better. There is also a brace available to tie the two sides of the front subframe together for better steering response. The IROC- and WS6-optioned cars came equipped with these, but the aftermarket-sourced ones are generally more rigid. These prevent the subframe from cracking at the steering box mounting point, which is sometimes an issue with these cars. There are even gussets available to brace the lower A-arm mounting section of the K-member (sub-frame) to the unibody for more rigidity.
Geometry isn’t really a problem with these cars but flimsy suspension components are. One look at the factory Panhard bar leaves you shaking your head. It’s a thin U-channel with very soft bushings on both ends. This is not the best thing to laterally locate the rear axle under heavy cornering loads. Upgrading to a more rigid tubular bar with low-compliance bushings is a great idea. If you intend to lower the car’s stance, an adjustable Panhard bar lets you re-center the rear axle under the car.
One area where there is room to improve the design is to substitute a Watts link for the Panhard bar. A frame-mounted Watts link setup adds a new crossmember and more chassis rigidity as well as improving dynamic handling. The lower trailing arms are also flimsy; in fact they’re basically the same arms used on the G-body. All of the previous tech information on trailing arms applies here, too.
Because this is a torque arm suspension, you don’t have to be concerned with upper trailing arms, but the torque arm can be a matter for concern. If you’re trying to harness a bunch of horsepower, you’ll want to upgrade the factory part to prevent deflection under heavy acceleration. Be cautious of the front-mounted bushing design. It needs to be free to move fore/aft without binding as well as being able to move freely in torsion. Normally, these bolt to the transmission tail-shaft and transfer a lot of stress to the transmission mount, so if you want to plant some serious power, consider one that relocates this mount to the sturdier crossmember.
Aftermarket torque arms are generally adjustable for optimized pinion angle, which is a plus. Torque arms are generally not known for having great anti-squat, but you can improve this (usually at the expense of increased roll steer) with weld-on lower-trailing-arm relocation mounts. These drop the rear of the trailing arms to increase anti-squat and traction.
The third gens don’t have a subframe per se; they have more of a Mopar-style K-member. There are no geometry gains to be had by changing to a tubular one, but you can pick up some extra chassis rigidity while losing a little weight. They can be had configured for big-blocks and LSX motors if you’re doing an engine swap. Because they’re not full subframes, aftermarket K-members cost a fraction of what the full subframes for earlier Camaros or Firebirds command.
Written by Mark Savitske and Posted with Permission of CarTechBooks