How do I identify which spring I have? I have no idea if the spring I have is original or not. The number on them is 621B320. The car has a non-original 400 small block chevy in it, and the car originally came with a straight six (according to the vin number). Its a 1967 Plain Jane Camaro Coupe by the way. At the very least, if these are the original springs, they are not stiff enough because of the added weight from the V-8.

Has anyone ever tried to measure the spring constant (k) manually? I am envisioning putting the spring on a platform, then measuring the uncompressed height, then adding a few hundred pounds on top of it (on a piece of plywood, for example)...maybe an old engine block or something, then measuring the compressed height, then calculating what the spring constant is (k = Weight / distance compressed). I'd need to know the exact weight I was putting on the spring, and I'd have to have it rigged up so it was relatively safe to do so the thing didn't "spring" out and hurt me. I'm not sure why everyone refers to the spring constant as the spring "rate". The "rate" is a term really meant for describing the dynamics of the shock absorber...just me trying to analyze things too much as usual.

Moog springs are rated at normal load height, so the "rate" is pretty accurate if you have that amount of weight on the spring.
The Moog catalog shows a spring load of 1800 lbs 327 lb/in rate for a 69 Camaro with 350 or 327 and no air non-convertable.

a 69 6 cyl shows 1644 lbs load and a 288 lb/in rate spring. both spring heights installed and loaded are 10.75", 67 is pretty much the same in all respects.

It would take a pretty stout frame to handle that kind of load for rating it correctly. There are some on-line rate calculators but the type of coil ends and seats makes a big enough difference in the result that it's not too reliable.

A guess would be if there is a stamped number on the spring, that it's not a stocker. The number doesn't look like a Moog number at least I can't find it in my very old Moog catalog. The "320" at the end might be the rate.

I would recomend a stiffer spring for better handling. If you want the car lower, a stiffer spring is better for keeping the headers from scraping and the car from hitting the bump stops.

Lots of people are using the Moog 6308 which sets the car a little low but has a stiffer rate of 380. This is a Nova ft spring and is used on Camaros with 6 cyl. I believe it is equal to a Z/28 stock spring. Z/28's are not listed in the Moog catalog, at least not mine.
David

You can make your own spring 'checker' out of a bottle jack, some steel 'U' channel and a pressure guage. I have also seen some home made models that used a steel pipe affixed on one end to a wall (used as the piviot location) and a scale on the floor.....just put weight on the end of the non-fixed pipe end, calculate the motion ratio and read the scale. But definately take into mind on how to affix it to a 'saftey' line (cable or other) as you are right about kinetic energy, it isnt too fun to play with when it gets out of control.

Concerning "rate", it is a term used to describe a relationship of a quantity measured with respect to another measured quantity. It is not only a term used to describe dampers (aka shock absorbers), as in this context it is mearly used to describe a ratio. Because there are different spring types, using the word 'rate' is applicable since one of the spring types is not a constant model, or in other words linear. But in its simplist terms, 'rate' is half the difference between the loads 1-inch above and 1-inch below a specified position, which defines it as a ratio.

A simple measure to calculate the constant is to invert Hooke's law, where the calculated constant k is the product of force divided by the difference of free length, minus the deformed (compressed) length as described previously by you.

The design and enginnering approach can be used with the major, the minor and mean diameters, the wire diameter, the number of turns and the distance between the coils and the overall free length. There's a lot more too it, but getting into the explaination of shear modulus of elasticity and the characteristics of HD class 2 High-Tensile wire is something I will leave up to the one who wants to take it that far.

Here are a few links to the related terminology and mathematics:

Coil spring math .PDF (http://www.misumiamerica.com/technical/pdf/usa_pdf_tech_p1361.pdf)

For specific linear rates .PDF (http://www.cheresources.com/dkspringcalc.pdf)