In 1969, Chevrolet built a very limited number of Camaros equipped with the legendary 427 cubic-inch ZL1 V8. Dressed down in luxury options to make way for the finest performance hardware Chevrolet had to offer – in grand sleeper tradition – these rare models are referred to as the COPO (Central Office Production Order) Camaros and have become some of the most highly sought-after musclecars today.
Fast forward to 2012: Chevrolet revives the COPO moniker, but this time the game plan is a bit different. Using the fifth-generation Camaro as a canvas, Chevrolet Performance produced 69 examples of its new interpretation of the COPO model – a factory-built NHRA Stock Eliminator drag car specifically for use on the track. Along with a host of other track-specific upgrades, the COPO Camaros also ditched the standard Camaro’s independent rear suspension (IRS) for a more launch-friendly solid axle setup.
All told, the COPO Camaros offered from GM proved to be a formidable package, but with only 69 cars built in total, putting one in your garage is easier said than done.
As it turns out, getting your hands on a rear suspension setup like the one found on the COPO is just a matter of getting on the line with the folks at Moser Engineering and ordering up their solid rear axle package. So, that’s exactly what we did. We put our wrenches to a 2014 Camaro SS that was previously using the stock suspension components.
Our New Solid Axle 5th Gen Camaro – Project True SStreet
Our car, Project True SStreet, is a 2014 Camaro that’s destined to be a street and strip bruiser, packing a Whipple supercharged Chevrolet Performance LSX376-B15 (engine build story, on the dyno part one, and on the dyno part two) powerplant and similar styling cues of the inside and outside of the real COPO Camaro. Moser’s solid axle package will provide us all the frills of the COPO’s suspension package, but with additional adjustability.
While the stock Camaro’s IRS is a great setup for a street car in terms of handling and ride compliance, getting independent rear suspensions to hook on hard launches can be tricky. That’s compounded by the fact that IRS systems typically add a lot of weight to the car versus a solid axle alternative, and usually aren’t designed to withstand the abuses of high horsepower applications. With that, it’s clear that if you’re putting together a purpose-built fifth-gen Camaro for the strip, replacing the independent system with a solid rear is the way to go.
“Let’s face it, no independent rear with even the best half shafts is going to handle sticky meats and 1,500-plus horsepower and high RPM launches reliably at the drag strip,” says Moser’s Jeff Anderson. “Horsepower is more affordable than it has ever been, and when you see 1,500 horsepower and higher becoming more common, you need a solution.”
The center section, along with brakes, driveshaft, and shocks aren’t included with this particular kit, so you’ll need to supply those yourself – which makes sense considering the wide range of different setups racers will inevitably want to run. Moser does, however, also sell a full kit with all said components if you require a complete strip-ready application out of the box.
“This rear was basically developed as a single package replacement for the fifth-gen cars that are interested in racing Stock Eliminator,” Anderson added. “It allows a person to make his own COPO conversion without the huge price of admission required by the factory, and they can do it slowly as time and money allow.
“Although it was initially designed for NHRA Stock Eliminator classes, the simplicity allows it to be adapted for many classes or uses, including extreme high-horsepower street cars that are more interested in straight-line performance. It was designed so that only minimal modifications are required for this kit compared to other designs in the market, and comes with all the adjustability you need for competition right out of the box. This is a serious rear assembly for machines that mean business,” Anderson continued.
It should be noted that, like the OE setup in the COPO, Moser’s solid rear axle package is NHRA-legal for Stock Eliminator in a non-adjustable configuration.
For this build, we sourced a set of JRI’s Sportsman Series Double Adjustable shocks from Moser, as well (PN 400164). These dampers include a coil-over kit and are made from lightweight aluminum. The shocks use a monotube design for added grip and offer a wide range of different ways to set them – their three-way adjustability allows you to independently set compression and rebound to taste, along with ride height. They also sport a rather trick design that delivers its nitrogen charge without the need for an external canister.
We opted for Moser’s Thru-Bolt aluminum case as well. One of the strongest units on the market today, yet it helped us pick up a bit of weight savings, as well. The case is made of 206-T4 aluminum with 7075-T6 aluminum caps and billet steel adjusters, and its through-bolt design gives the case increased strength and decreased ring gear deflection that is common in most aluminum case designs.
Gearing Up For the Strip
While swapping out the rear suspension is understandably an involved process, it’s actually not as sizeable of a job as it might seem once you’ve made room for the new parts to go on – assuming you’re comfortable doing a bit of welding. As this package is designed to replace the entire independent rear cradle assembly, it requires the removal of the exhaust, fuel tank, and lines, and assorted sheetmetal crossmembers and bracing to allow for the installation.
To get things underway you’ll start by taking off the rear wheels — you’ll thank us later when you’re dropping the assembly out of the car — and then removing the driveshaft and disconnecting the emergency brake cable and other component wiring.
Along with the shock mounts, four main bolts attach the suspension cradle to the vehicle, and once those have been removed, the entire assembly will come out as one piece. You’ll also have a number of spot welds to drill out, so you’ll want to allocate a bit of time for that task as well.
Since the crossmember for the forward torque arm mount needs the adapter plates welded in to the sub frame rails, you’ll also want to remove the seats, carpet and any insulation that may burn as a result of any cutting or welding. The car needs to be supported on all four corners so that the rear cradle assembly and associated parts can be removed without interference. To get a better sense of what’s involved in the install, check out the step-by-step installation instructions here.
There are six sheetmetal pieces that need to be removed to facilitate the installation of the subframe assembly, consisting of the upper crossmember, charcoal canister brackets, e-brake cable guide, and the tunnel support bracket. It is recommended to use a spot weld drill or cutter to remove these pieces. Once they’re out you should have enough room to install the sub frame assembly.
We didn’t run into much in the way of hurdles along the way, aside from one pesky bolt that didn’t want to make room for the new subframe to go in. For added rigidity, we fabricated some subframe connectors to hook up to the new subframe, as these connectors provide a way to transfer more of the load to the chassis, rather than the bolts themselves being solely burdened with the task.
After the anti-roll assembly, front crossmember, forward control arms, panhard assembly, anti-roll adjusters, shocks, and associated hardware have been bolted up, the housing assembly can be installed. Those with 12-bolt rears will be ready to go, while 9-inch housings will at least need the center section installed. If you are using a 12-bolt, you’ll need to install the torque arm housing adapter using the supplied four 1/2-inch by 1/2-inch coarse thread bolts and locking washers. Moser highly recommends using Red Locktite on these bolts.
The torque arm has a nine-inch long, one-inch outer diameter tube that slides in and out of the front of the torque arm that allows for rear suspension movement without binding – it’s important this “slider” is kept lubricated at all times, and there’s a grease Zerk fitting on the torque arm for this reason. Thread a 3/4-inch jam nut all the way onto the 5/8-inch by 3/4-inch moly heim joint, and apply anti-seize to the threads and thread the heim joint fully into the slider. Tighten the jam nut against the slider.
The COPO Retrofit Design
One of the criteria for Stock Eliminator is that you must have a fixed lower control arm, and the brackets on the chassis and rear axle housing cannot have multiple holes – there is only one position where the bars can be located.
Given the guidelines presented by the NHRA, Chevrolet had clear marching orders when designing the COPO Camaro’s rear suspension. The result was a four-bar, upper and lower control arm design that would later provide the blueprint for Moser’s kit.
The lower shock mounts attach approximately mid-point on the adjustable housing mounts. There are two left hand brackets and two right hand brackets, and the shocks attach using two 1/2-inch by 2-1/4-inch bolts, washers and nuts.
Depending on the width of the lower shock bearing, spacers may be needed to make up for the clearance between the mount and shock bearing. The Panhard rod centers the rear end and wheels and tires in their respective openings.
At ride height, you can lengthen the bar to move the rear end to the right of the car and shorten it to move it to the left.
Once everything is centered, tighten the jam nuts to secure. Install the axles, brakes, and miscellaneous accessories to get everything buttoned up – but don’t forget to add gear oil.
The first place to start when making initial adjustments is the shock ride height – set it to the manufacturer’s default factory-recommended specification. If not available, set the shock at 60 percent compression – the spring seat should be at midpoint of the threaded adjuster.
From here, set the control arm level by raising or lowering the lower adjustable shock mount on the housing. On subframes and housings with adjustable control arm mounts, the mounting points of the control arms can be raised or lowered to achieve a level control arm.
The pinion angle should be set at one-degree more than the engine angle. For instance, if the engine is at a three-degree downward tilt to the rear, the pinion should be set at two-degrees up in the front. The goal here is to get the pinion and the drivetrain centerlines to be parallel under power. Increasing pinion angle increases “hit” to the rear tires.
The anti-roll arm controls body roll at launch and braking. Typically anti-roll adjustments will start at neutral or no preload and go as high as one full revolution in length to keep the front end level at launch. Setting up the anti-roll so the car launches straight and lifts the wheels evenly is accomplished by increasing or decreasing the length of the anti-roll adjusters.
Shock dampening should be set to manufacturers recommended specifications. Loosen or tighten dampening as needed. Note that you can control body roll characteristics by tightening compression on the right side and tightening extension on the left side.
Torque arm adjustments are made after initial runs are made. Raising the front of the torque arm front mount increases rear lift, lowering the torque arm increases front end lift.
Keep in mind that all of the above recommended specs will be determined by the actual combination you’re using in terms of tires, engine output, torque converter, and a number of other variables that may be unique to your build. Now get in the garage and start wrenching!