My car is basicly stock(weight) except for Hardwood hood and Weld wheels(which doesn't matter). It is a fully loaded 1992 Z28(5.7). I have searched and I believe the factory front spring rate is 548Lbs per inch.

Am I wrong?

I have 200lbs (10") coil overs I am installing. I jacked up the a-arm and it compress(to almost coilbind) until it lifted the car. I tighten the coil over up about 1/2 way and still no luck.
This is my fault, I ordered them for a race only car(less weight) and desided to play around with my daily driver.

What spring rate do you think I would need?
I want a softer spring (for dragracing) and want to keep around my factory ride height(for ground clearnace).

I saw in Jegs 250,350,450 rated springs..which ones?
Should I call P&A and get them from them?

thanks

 

If you are using a 10" coil (free length) you would on average shoot for a spring rate that will compress the spring 1" when fully weighted in the car. For drag you would want a spring that will unload more travel on launch so I would recommend one with more like 1 1/2" -2" compression alotting for sufficiant travel without coil bind (2" my be pushing it to close though, every spring is different based on rate/to coil bind ratio diameter of coil used.)

It is always pretty much a guessing game to get it right unless you know someone that has tried different combos on the same weight/and design suspension vehicle. If 200lbs are too soft, I would recommend not trying more than another 100lb bump up for coilovers, that can be a big increase and you want to stay on the soft side. Your own suggestion about asking PA for advice is a good one, they deal with different rates more than any independant car buff. But again, I would suggest trying 300lbs next- most vendors will allow you to swap rates for free with a new application until you get it right.