I'm looking for advice on selecting front springs for a small block (probably with Al heads) 65. I'm considering going with the QA1 Pro Coils for the adjustability along with the ATS spindles once the early A steering arms are available. The progressive spring rates listed on the QA1 site are 250/350 lbs. for small blocks and 365/465 lbs. for big blocks. I know personal preferences play a big part of what 'feels' right, but I would like to get advice from some who have tried different spring rates. I want this car to handle well, but don't want the front end to bounce around like some highschool kid's butchered Civic. Stiff is OK if better handling is the payoff. Jittery and all-over-the-road with the CD skipping is not an option. Will the change be that severe with the BB springs, or will it still be easily driveable only stiffer/more responsive/etc? I really have no point of reference here so I'll appreciate any input you guys can offer.

Shocks take care of the bounciness but the spring rate affects stiffness when you hit a bump. Someone put caddy springs in the rear of my Chevelle, and it felt like their was no suspention at all and the rear was as high as the shocks would let it. I would say for a small block with aluminum heads go with the sb springs for stance and ride quality. Thats just my opinion.

For comparison, my bigblock convertible with aluminum heads has 488 lb/in spring rate and it feels very firm, but not harsh. However, any firmer and it might feel harsh.

My hardtop, with a bigblock and aluminum heads and a fiberglass hood has 360 lb/in spring rate has a nice ride and has what I would describe as a medium firm feel.

I also have a 70 Cutlass (350) with 327 lb/in spring rate, and that is a little too soft.

Of course this is all subjective, but might help with your selection.

Bounciness is a perception and can be caused by shocks *and* springs. The spring affects how much the wheel is allowed to move over a bump. The shock mostly affects what happens after that. The reason you see Civics hopping all over the place is that the suspension is not being allowed to move, much as would happen with a Chevelle with springs that are too stiff (or all poly in the rear ;) ).

Your combination is small block with less weight so small block recommendations are likely closer than big block recommendations. But I would question those numbers for SB. The way Chevelles are setup up front requires serious spring rates. Let's say, for discussion, that you have 2000 lbs on the front tires. That makes for 1000 lbs per tire. So to hold the car up there needs to be 1000 lbs pushing down on the tire.

But the spring is halfway up the LCA so rather than 1000 lbs it takes 2000 lbs. So if the fitted spring load is 2000 lbs it will take 8" of compression of a 250 lb/in spring. Now we put a big butt (or 2) in the car so the tire is supporting 1125 lbs, spring sees 2250 lbs, and that spring drops an inch.

But wait, the spring dropped an inch... and remember that the spring is halfway out the LCA so the wheel actually dropped 2"! That 250lb spring actually provided a rate of around 60 lbs/inch.

Welcome to the concept of "Motion Ratio" and "Wheel Rate". The MR takes into account the leverage between tire contact and spring and the WR is spring rate * MR * MR. WR is more useful because it tells you what is really happening.

So those QA1 specs look like 62/88 SB and 91/116 BB. I drive a 3600 lb Mustang with a WR of 150. Tastes will vary but I find this setup to be about as stiff as I would go on the street. Provides great handling in the twisties but is sometimes annoying on poor quality city streets. Would suggest that the BB springs might not be too bad, maybe a bit soft, since I think the Chevelle is actually not too far off weight wise to my Mustang.

I installed 700# springs in mine... haven't driven it yet, but I'll know in 3 months if I like it.

A 500# spring would probably be a good choice if you want good handling, and a decent ride.

Oh... forgot to mention that front spring rate needs to be coordinated with rear spring rate. You will get another kind of bounciness if you have stiff on one end and soft on the other. That is what I have on my Elky now, soft fronts and stiff rears. Pretty typical El Camino setup unfortunately.

This is also why you often see vendors selling performance springs in the full set of 4.

My 67 SS big block had 320 lb, which was very soft, I went to 384, still too soft, finally went to 440 and that rate works without being too soft or too harsh. Just my two sense. :D

I've got 1000lb springs in the font of my chevelle and 175's in the back. This is also a big block chevelle with iron heads but i'll let you know how it rides when i get it back on the road. On a side note, i had hotchkis sb springs in there before these and i think they're around 550lb but the ride was alright, had a little too much weight for the springs but the frame was in bad shape too so i can't blame it all on the springs.

I have hotchkis Technically sb springs i am installing in my 70 chevelle. It is in a 427 bbc car with AL intake and no ac, PS and brakes though so we will see. The springs came with the car uninstalled so i am going to see how they do... Really though when looking at the hotchkis site the spring rate is 500 lbs/in for both the BBC and SBC springs. Are the bbc ones just longer? It says also that for the SB springs they can go with a BB with AL heads/intake so i should be at least close.

Daniel

Thanks to all. vroom brought up matching the f/r ratio. Is there general guidance on how to match them without a 4-spring set (i.e. rear should be 50%, 25%, etc of fronts). If I go with the BB QA1's (though from some of the posts it sounds like I may want a little more to get what I'm after ~500lbs or so), what should I be looking for out back?

On a side note, these cars' weight ratio in stock form is roughly 60/40 f/r, right? On a side-side note, I think I need to back up and learn some suspension basics before I break out the $$! Thanks for any more help you can dish out; meanwhile I'll delve back into more searching through the old posts.

First note that the *spring* rates will vary substantially between the front and rear. The motion ratio of the rear is almost 1:1, so spring rate is pretty much the same as wheel rate.

Sounded to me like 500 lb fronts were about right from the discussion as well. That works out to a wheel rate of 125. So without getting all technical here, you want a bit higher rate in the rear. I might SWAG it at 140 maybe 150 lb springs in the rear. But I could be off there since I have not factored in weight distribution.

To do this right you need the weight at front wheels and back wheels. Then you use that and the wheel rates to lookup/calculate the "natural frequency" of the suspension. Then you select rear springs with a slightly higher NF than the front. The idea is that after going over the same bump both ends recover at the same time. But since the rear hits the bump a bit later than the front, it has to go faster to finish recovering at the same time.

I did this technical analysis on my Mustang when I converted over to IRS. Similar weight and similar distribution to Chevelle. IRS had motion ratio close to front. Ended up with 600 lbs rear to match the 600 lbs front. Suggests you might want 125 lb rears with your 500 lb fronts on the Chevelle.

only thing I see thats been overlooked in this spring recomenditons list is how much swaybay to put with what springs.... makes a big difference between running a 7/8 stock bar & 1 1/4 swaybar no mater what springs you put them with ... I'm running a 1 1/8 bar with 375 lbs springs in a small block El Camino & Love the improvement over the stock setup :) ride is not harsh or mushy rear is f41 style setup 7/8 bar with stock rear springs & airbags adjusted to my load or driving prefence .. my 2 c

Comparing a front coilover spring rate to a conventional coil isn't the same,I don't think. Before I switched to Air Ride,I was running the QA1 coilovers w/BB springs on the front of my 69 w/SB. The ride was very harsh. I would definitely try the SB springs,first.

Comparing a front coilover spring rate to a conventional coil isn't the same,I don't think. ...
Actually in the Chevelle chassis they are exactly the same since the shock runs right down the middle of the conventional coil.

Now on something like a late Mustang... then there is a pretty big difference.