One benefit of the Pro Touring movement is an appreciation for a performance suspension. Car guys now think both in terms of more power and how to improve suspension control with components like shocks, springs, anti-roll bars, and tubular control arms. While in the beginning stages of our ’66 SS396 Chevelle chassis restoration we decided to upgrade the suspension with an Aldan coil-over chock conversion.
Looking back at the original configuration of this Chevelle, the suspension now seems archaic. From the factory, this car came with a 360-horsepower 396 big-block, Muncie four-speed, tiny 9-1/2-inch drum brakes, weak springs and shocks, and a pitiful manual steering box. We’ve upgraded to ’68-’72 disc brakes, a quick ratio steering box and now it was time to think about shocks and springs.
Initially, we partially reassembled the front and rear suspension with Global West upper front and tubular lower rear control arms but didn’t torque everything in place. This allowed us to quickly disassemble the original package and install the Aldan coil-overs. We’ll run through the normal installation procedure to reveal how easy this conversion really is along with some additional information on front suspension alignment.
Reasoning For Rebound
To increase the overall suspension tunability, besides the ability to easily change ride height, these Aldan shocks are also adjustable. This means that via the small adjustment wheel on each shock absorber can modify the stiffness to adjust for handling or to massage the ride quality. For this application, the front shocks are single-adjustable for compression only, which means that the knob adjusts valving stiffness only when the rod moves into the shock, as when responding to a bump.
The rear shocks are also single-adjustable but in this case only in rebound (extension). Aldan also currently offers double-adjustable shocks for the rear and should have double-adjustables for the front by the time this story is published. As their name implies, double-adjustable shocks allow independent adjustment of both the compression and rebound valving.
Of course, one main advantage of coil-overs is that ride height can be easily and quickly altered. But keep in mind that a change of ride height either at the front or the rear will affect the front-end alignment. Ride height changes at the front will generally affect all three settings of camber, caster, and toe.
A change to rear ride height will mostly affect caster. Lowering the rear will add negative caster. Positive caster is the rearward tilt of the top of the front spindle and generally improves high-speed stability. Stated another way, lowering the rear will decrease the amount of positive caster and can decrease high-speed stability. It’s important to keep these changes in mind when altering ride height.
Camber, Caster, and Toe... Oh my!
The three main measurements when it comes to the alignment of your wheel and tire to the chassis are camber, caster, and toe. Each of these settings has benefits and drawbacks, discussion of which could take a whole article in itself. So here are the basic definitions of the terms:
Camber is the tilt of the wheel vertically, inward or outward from the center of the car. Positive camber puts the top of the tire out further than the bottom of the tire. Negative camber is when the top of the tire is more inboard than the bottom of the tire.
Caster is the vertical tilt of the axis around which the wheel rotates when turning left or right. Zero caster would mean the axis is perfectly vertical. Positive caster would lean the top of the axis rearward, while negative caster would put the top of the axis in front of the center of the wheel.
Toe angle is the direction of the leading edge of the wheel and tire in comparison to the opposite wheel and tire. Toe out (or negative toe) would mean that when the steering wheel is centered, both front wheels point outward. Toe in (or positive toe) is the opposite, with the front of the tires pointed inward.
We’ve also included a generic front suspension alignment recommendation for 1960s and ‘70s muscle cars that will both improve handling while not drastically affecting tire wear. Many ‘60s cars used very low positive caster and actually positive camber as stock alignment specs. We’re not sure why these specs were called out this way as the result is only to increase the car’s tendency to understeer quite badly.
This entire conversion can easily be done in your driveway with some simple hand tools and we were pleasantly surprised at how easy the process really was. So follow along as we show you how to upgrade a mid-’60s suspension to coil-over status with adjustable shocks.
Here’s the completed coil-over conversion. We may trim the upper bolts slightly to ensure they do not come in contact with the body. One additional advantage to this system on early Chevelles is that the lower shock mount is moved inboard, creating much more clearance to the inboard tire sidewall compared to the original factory location.
|Spring Rates for Big-Block Conversion Kit|
|Suggested Initial Alignment Settings|
|Camber ½ to ¾ Degree Negative|
|Caster 4 to 6 Degrees Positive|
|Toe-In 1/16-inch Total (1/32-inch per side)|
|Front and rear coil-over kit, single adjust 300103 Aldan|
|Thrust bearing kit ALD-26 Aldan|