When I had bags in my Mitsubishi minitruck, and I raced Hondas. I know a jap racing more jap crap. But i had a cam, headers, no cats and some head work. It would keep up with the EX Civics.
Anyways, I would let the back almost all the way down, not all the way because my roll pan would drag, truck was body dropped also. Just enough that the back would dip and nothing would drag. The front I would lift a little higher, not all the way, but higher than the back. It worked pretty good. That was a truck with no weight in the back either. SHould work better with a big sled like a Cad.
TomSS' suggestion of 19 lbs for a 1.80 60' sounds about right, maybe a little low from my experience. The harder your car is capable of launching, the more body twist, and the more differential pressure you need. 30lbs in my right bag and almost nothing in the left was good for a straight 1.63 60' with a dead posi.
Here's how I "tuned" the bag on NA launches:
Launched with hands off the wheel. If the car headed right, that told me I needed more air in the right bag. You might be surprised at how much you really need. When it's correct, there should be very little posi action required.
Looking Into getting a whole new suspension kit for 96 impala. Had for about 10 years now just sitting, so like to bring her back to life with a while new upgrade rear and front suspension including shocks/struts. Just put a new battery, fresh Royal purple oil, k&n oil filter, and k&n air...
I'm working on a project that has B-body frame clips. I installed the Hotchkis Impala SS springs, but it's REALLY low in the front. I had a set of SS springs, but sold them to a local member. Now I'm thinking I need something more along the lines of the Global West springs (closer to stock SS...