I will be installing a set of QA1 double adjustable coilovers on the rear of my '72 Skylark. I have two sets of new springs (150 and 200 lbs/in). I'm trying to decide which to go with and I have no sense of how either spring will feel. The car will see mostly street use with an occasional 1/4 mile pass. I highly doubt I'll autocross it, although eventually I'd like to go with the pro touring look. Any opinions would be appreciated.
Only thing I can quote is the 1970 GSX had a front spring rate of 450 lbs/in. and the rear was 144 lbs/in. I believe the stock F41 package was less stiff as I think they wanted a better handling car with the GSX. I haven't read of any complaining of excess stiffness with the GSX. Coil overs might rate and drive different though?
when I did put mine together,I went with a set of springs for the rear from a 70 GS 350 original.Almost the same cam as yours.Mine is 242-258.Car is over 4000 pds,short time in the 150's,with a 12 bolt with 373 gears and no-op bars and 2 air-bags.Bruno.
QA-1 recommends the 150 lb spring for the A-body: https://www.qa1.net/assets/uploads/documents/general/Spring-Rate-Chart-Vehicle-Weights.pdf You're within range of either the 150 or 200 springs, so you made a good starting choices. Their charts do suggest increasing the rate for heavy options such as A/C or a big block. That may push you towards the 200# if so equipped. A softer spring would work better for drag racing where weight transfer is the goal. A 200# spring is on the stiff side unless you want to improve cornering ability or haul lots of groceries. If you're driving on nice roads, the 200 may be fine. If your roads aren't the best, the 150 would give a more comfortable ride.
Walt - I did see the first chart from QA1 and I was a little hesitant about using the 200 lbs/in springs since the chart lists the 175s as firm. However, I didn’t pay attention to the second chart which recommends adding 25 for a big block. (I don’t have ac.). Maybe the 200s won’t be bad, and stiffer may be better if I eventually go for the protouring look. Thanks.
Nice chart. Even showing rates for added AL heads and - rates for cars with no PS or PB.. A bit off cuff but wow look at the spring rates for the C5 vette! I find it weird that the 78-88 G bodys need a stiffer spring, aren't they alot lighter? They have the BBB in the same rate as BBC?
Around town I leave all alone,at the track,did I mention 2 air bags?,I put 10 pds on the driver side,30 pds on he passenger side.Now I know its not too scientific,but my short time is fairly good.And ,if I did not have a race car,I would put a spool in the rear,that would cut down the short time a lot,as I would have slicks with the rear gears.Bruno.
Yeah I saw that. 3 times +/- more than the other vehicles. Crazy. That’s an understatement. I’d say it’s impressive.
