View Full Version : coil over spring rate?

10-05-2004, 08:09 AM
I'll get the Koni aluminum single adjustable coil overs for the front suspension on my 1968 small block chevelle.
As for the stroke I'll get whats closest to the C4 front shocks, but Jegs does not tell which lenght of spring to get (10" 12") for which shock.

And what spring rate should I use?? 500lbs/in, 600lbs/in, 700lbs/in???? I know its difficult to tell but a guess is appreciated.

same question for the rear C4 suspension, which spring rate is a good starting point ??

Thanks !

Ralph LoGrasso
10-05-2004, 02:20 PM

On my '68 Camaro, I'm using the DSE valved single adjustable Koni c/o's and I'm going to start with 550lb springs. I believe DSE recommends 550 for SBC first gens, I'm going to be running an LS1, and no inner fenders, so it will be even lighter. I may step up to a 600, or 650 but I want to see what the 550's will do first. I was planning on the 600s initially, but after talking to a few people about it, they said to hold off on them. For the track I'll run 700 or higher.

For your Chevelle, I'd say if you don't mind a stiff ride, maybe start with the 600 or 650, depending on whether or not, you have aluminum heads/intake.

edit: Are you using C4 front suspension? I know that the WD spring rates for his C4 (first gen) frame are much less than "normal" due to the C4 suspension design and configuration. Hopefully some A-body and C4 guys will chime in here.

10-05-2004, 03:28 PM
If this is a Wayne Due subframe those spring rates will turn your car into a skateboard. With a big block I only ran 300# springs. 400# and you could not even get the suspension to move. It all depends on where the shock is mounted in relation to the lower ball joint and some other measurements. Get ahold of David Pozzi; he helped me with mine. Had me make some measurements and we figured out that a 500# spring (what I started with) was equivalent to a 900+# factory spring up front!


10-05-2004, 11:25 PM
Thanks guys!
Its all homemade, I am building new framerails myself from the cowl forward and use the original C4 crossmember.

I thought of using the original lower shock mount on the a-arm and make the upper one to fit once having the shocks in hand.

camcojb, are you willing to take some closeup pics and e-mail them to tigergutt@tigergutt.biz then I can use them as an idea.


10-06-2004, 06:56 AM
I don't have the car anymore. It belongs to a member here, Stuart Adams. It will be at SEMA this year in the Optima battery booth if you're going. Here's a couple of pics I have on my website.


10-07-2004, 11:20 AM
Hi again,

David Pozzi, if you read this wuld you be so kind to comment.

Jody + Ralph
I'll go for the 300lbs ones up front as a starting point then.
But which shock rate should I use at the rear of the car ?? it is a dana44 c4 rear-end (hey is that not the same as bum? :3rd: )

I have figured out that the shocks to use both front and rear are the Koni single adj. aluminum shocks with part #82161906SPA1 (Jegs 610-82161906SPA1)
They are 15 1/2" ext and 10 3/4" compressed having 4 3/4" stroke, the problem is that I cant find anywhere which lenght of spring to use... 7", 8", 10" or 12" ???? Anyone knows

SEMA... I'd love to be there but it is a little bit to far to travel, I live in Europe (I am Norwegian but live in Italy)

Thanks for the pics, the pics are beautiful

Thanks André

David Pozzi
10-07-2004, 10:37 PM
Without knowing a lot about the detalis I'd guess at a rear spring rate of 200 to 250 lb/in. You might wind up with a heavier spring closer to 300 but that's my best guess.

Front shocks:
Check what the travel will be with the bump rubbers on the shaft. The bump rubbers further restrict travel unless you are going to leave them off and use other bump stops on the chassis.

10-08-2004, 12:41 AM
thanks for replying.
I measured the stroke on a std c4 rear shock which is 4 3/4" that is excactly the same as the konis I looked at.

on the front, using the same Koni shock the stroke is 1 1/4" longer than the std c4 (3 1/2") so that bump stop wont create a problem up front.

spring rates for c4 front and rear suspension an 1968 chevelle.
Rear 200 to 250lb/in
Front 275 to 325lb/in
what do you think?