The springs are rated for the weight of the car.
Yes, that was the original intention for a Super Stock car on a smooth race track.
Over the last 3+ decades, I tried to find a suspension set-up that worked, rode well on the street and road courses and held up to the rigors of 500+ & 700+ horsepower. I tried several variations of SS leaf springs including mono-leaf Caltracs. They results were a brutal ride, constrained compliance over road imperfections, less traction on non-smooth roads, but decent performance on a smooth track.
My quest for a balanced spring rate for a street/ strip car continued for years. I tried both the 3700lbs SS springs and the 3400lbs SS springs, and both were brutal on the road and so stiff the cars actually spun way more with them than the much lighter 2800 lbs SS springs with slapper bars. The ride of Caltracs was brutal as well, but the car launched well on a smooth surface.
In frustration, I sought advice from Dr Diff, aka Cass. He knew from experience about the high spring rates, and advised me to try the 2800 lbs springs. I thought no way, the spring rate numbers are way off. I'm so glad I listened, because now I have the perfect spring rate for a car that is 1000 lbs heavier. I never would have tried them without his advice.
There is one caveat with this formula though. The lighter springs can not control the spring wrap in high torque applications by themselves. I tried a pinion snubber, but that essentially locks up the movement of the rear suspension while stopping the rear end nose from rotating upwards. This results is a brutal ride quality and a nearly ridged rear suspension that's great on a smooth track, but unusable on the street.
Knowing I had to do something or I was going to bend the front spring segment, I bolted on a set of properly adjusted slapper bars with 1/2 the rubber snubber cut off. (Before I put slapper bars on my '70 E-Body, I did end up bending the passenger side 2800lbs SS spring, and had to replace it.) I had to cut and weld the bar mounting perches to get the rubber snubber positioned directly under and just touching the front spring eye. Once I set them up like this, the car launched harder than ever, was compliant on the open road, and I knew I had finally found the holy grail of Mopar rear suspensions. A smooth compliant ride, the perfect rake and better traction than anything I have experienced in over 3 decades of searching. I will never run anything else. The path was long, but the difference is epic...especially with a pair of proper length quality shocks like Bilsteins or Koni's.
