After researching SPIDS and spring tags and such, the F41 suspension on the G-bodies, for the most part, uses LOW spring rates. One thing that surprised me a little was that many Monte Carlo SS's SPIDs I've seen has like DHK rear spring codes, which are on the absolute bottom of the GM parts list scale for G-bodies for 85-86 as the mushiest production spring rate. The lowest rate I've seen so far on 442 is DHN, which is one step above the HK springs. Mostly, the SW and PZ springs are found on 442, and sometimes a stiffer TS thrown in there now and then, and they're rather lowish in spring rate, but not THE lowest. Additionally, the spring rates COULD vary from side to side depending on the "computerized spring requirement calculations" or whatever they used to determine which spring applied to which corner of the car during production. Usually, there was only one spring step difference from side to side, such as in the front, one spring may be a DNZ and the other a DNY, but sometimes they jumped a few. And the service part replacement spring for both was the DNZ part number. Strange things. Confused yet?
84-up has a SPID, otherwise you'll have to be lucky and find the spring tag still attached or find your build sheet.
85-86 Monte front spring chart. The more common DYK was used in many a Monte SS, as well as 442.
85 Cutlass spring chart. Note DUJ is at the highest spring rate available for Monte Carlo, yet it's in the bottom 4 for Cutlass. I haven't seen any 442 with a higher rate than DUJ. Doesn't mean they don't exist, it's just many are DYK or DNY.
Another interesting thing is that as the years went along, by 1986 and 87, for the F41 cars anyway, they reduced it down to like 4 front spring rates. Going back to 1984, there were like 15 different spring rates. Even more weirdness.
I recall seeing some spring data on the stock springs a good while back, but I didn't save it or remember it or anything. Another one of those things that make you wish you did something different at the time. I'm sure it's out there somewhere.
Here's a low-mile 86 442 with SW and TS springs. TS isn't normally found on the cars. Only one stiffer spring than that was TA. The majority of 84
H/O's and 442s will show up with SW or PZ (or combination of those).
But you were wondering about your 78 Malibu stock springs. That would depend on what your door decal said as far as front and rear gross vehicle weight ratings were. This info is also sometimes found on build sheets at the bottom, usually. Maybe this chart below can help. (use 2.2 lbs per KG if you have to do any math conversions)
I found it was interesting the chart says to subtract 32 kg from the front GAWR and 36 kg from the rear GAWR if you have bucket seats.
Have you seen this chart?
