Editor's Note: Doing the same thing multiple times, and using your experiences to develop a better way every time, is what engineering is all about. It is this type of development that has allowed Mark Stielow to raise the bar on '67-'69 Camaro performance with every Camaro he builds. He has developed and built enough bad-boy Camaros to field an entire race-day lineup. The '69 "Thrasher" Camaro he is currently building revolves around the chassis and suspension. Having driven his last car with these modifications, it's obvious he knows what to do and that these changes work to improve the handling dramatically on early Camaros. Enjoy.
I have always wanted to have a '67-'69 Camaro that resembled the early Trans Am car "look" but with '90s handling and ride quality. To achieve that, I have spent a lot of time modifying the chassis and suspension on these early Camaros. Some of what I do might be considered rocket science, but for the most part, the changes I make to a Camaro can be performed by anybody.
I know from the last two Camaros I built using many of these modifications that the Thrasher should blast down the road with minimal bumpsteer, snap into corners, stop solidly time after time, handle bumps in the road with no problem, and be more comfortable to drive--all with over-the-counter aftermarket products. I expect the Thrasher to be the best handling, most comfortable Camaro I have ever built. Future plans for the car include competing in the One Lap of America, the top speed Pony Express 100 in Nevada, cruising cross-country in the Power Tour and more, so this car not only needs to do it all, but must also survive.
With this kind of challenge, I have chosen race-proven aftermarket products. Some of these components you might not have seen before, like the hidden spring jacks for the front suspension. All of these parts have been around for a while and have proven themselves capable. I modified them to fit this application, but they have proven themselves in the past, and I feel they will work quite well in a street application.
The stock Camaro front suspension consists of two unequal length A-arms connected to the spindle by ball joints, with the weight of the car resting on a coil spring, and a shock absorber mating the lower A-arm to the frame. A sway bar ties both lower A-arms to the frame rails. The steering on the '67-'69 Camaros are referred to as a "rear-steer" design, which means the steering box and linkage are located behind the front axle centerline. The rear suspension consists of a solid axle riding on parallel leaf springs controlled by shock absorbers. The leaf spring rear suspension is extremely simple, as the springs both support the weight of the car and serve as locating links for the rear end. With a few minor modifications, this rear suspension works quite well for a street performance application.
The modifications performed to the front suspension revolve around a pair of aftermarket lowered spindles I have designed. I also drilled new mounting locations for the upper A-arms, modified the spring bucket to accept a Landrum hidden weight jack and spring, and installed a Mullins-modified steering box and rag joint. I finished the front half off with Global West Del-A-Lum control arm bushings and a pair of Koni adjustable shock absorbers.
I also made a few changes to the front subframe which affect how well the front suspension controls the motion of the wheels. For the subframe, I prefer to weld all the seams, mount it to the car with Global West solid interlocking bushings, and weld homebuilt subframe connectors under the floor to tie the frame sections together. This stiffens the car body/chassis combination considerably, which forces the suspension to absorb the bumps instead of flexing the chassis.
On the rear suspension, I installed Global West solid body bushings, used Eaton dearched springs, (to get the proper ride height), and Koni adjustable shocks. To reduce unsprung weight, I chose a Currie aluminum center housing 9-inch rear end. This entire housing is about 25 pounds lighter than a standard 9-inch, and with its 3.89 gears, Tru-Trac differential, and 31-spline axles it can withstand all the abuse our 450hp 406 can dish out.
As the final note, Baer 13-inch front and 12-inch rear rotors were installed with a Master Power master cylinder/booster/proportioning valve package to put the big whoa on the show. This brake package is essentially equal to the Corvette ZR1 brake system, so it is certainly capable of stopping from high speeds and repeated abuse without fading.
Doing the Job
I have performed all these suspension and brake modifications a few times now and can say none of it is really difficult, but it is time consuming. I would recommend measuring your car for squareness or taking your car to a professional chassis/alignment shop to be checked before starting on anything, as these early Camaros can easily be tweaked. I have built "crooked" cars that never handled very well because of it.
Once you know the car is square, follow the old carpenter's rule "Measure twice, Cut once" when performing these suspension and chassis modifications. If the chassis ends up out of square, the trickest parts in the world won't make the car perform up to expectations.
The most difficult part of all these modifications is drilling the new mounting locations for the upper A-arm in the frame mount. I use a template that I built. If you carefully follow the dimensions shown in the sidebar you should end up with everything in the right place.
Onward and Upward
Stay tuned next month as we continue to hammer the Thrasher together. It's shaping up to be a car with plenty of potential. I can't wait to drive it.