I have a 1971 Malibu 350. I need stiffer springs in the rear (for clearance on a custom exhaust system). I am at stock height with generic Moog springs from OPG.

http://www.classiccarsprings.com/chevy/8chevelle.html

I see in this chart that there is no listed "Heavy Duty" spring for the 1971 350 Chevelle, like I was hoping. Just Cargo Coil... what's the difference. Will that be too stiff? Any other options you know of, based on these spring rates?

(I have QA2's on the rear, so I know I can adjust some of the damping to compensate...)

Thanks!

post a picture of what your car looks like from the side & rear. I don't understand why you need stronger springs for a custom exhaust ????

Standard and HD springs have a lb/in rating that's fairly consistant.
Cargo spring have a variable rate that gets higher (stiffer) as you add weight.

I have cargo spings on mine because 20 years ago I was using it to travel back and forth to college. They do not affect the ride but then again you do not feel the back end go down with a load.

The exhaust dumps BOTH before and after the rear axle. (I have an exhaut cutout so I can have either rumble UNDER the car, or behind it)
http://www.imagechicken.com/uploads/1219829521055881500.jpg (http://www.imagechicken.com)

The part that extends back goes over the rear axle, but on steep drops it sometimes climbs up and taps the exhaust pipe. I've had the pipe extended higher twice, but still some of the deep road things really pop it up there - the exhaust guy said he thought stiffer springs oughta help those rare extreme bumps - and they should.

Standard and HD springs have a lb/in rating that's fairly consistant.
Cargo spring have a variable rate that gets higher (stiffer) as you add weight.

So the extremes of travel would not necessarily change on a cargo spring?

What is the difference of an HD spring if it's not varied much from standard, I'm not clear on that (also do not see an HD spring listed here that applies).

Thanks -

The cargo coil will allow your car to sit at stock height. The heavy duty coil, your car will sit a bit higher in the rear.

Dave

Hmmm. Thanks - both sound like good options for reducing spring travel compared to the original stock. Height is the main diff to me...

why are your header dumps after the mufflers? doesnt that defeat the purpose?