Im thinking about running these..

[Throttle]

http://www.summitracing.com/parts/HAL-GMP3550-3/


Im been sitting here dreading the day Im going to have to put the Hotchkis Springs up front and knowing im not going to like them, so I decided that Im just going to put the Coilover setup in there that fits to my Lower Control Arm and Upper Spring Area..

Question is, are they worth doing?? I mean I know I can get the height I want out of them, but are they a good product to use under a car that will see a little bit of track time but more street time.. Im not sure what I need spring rate wise, I have a Aluminum Headed BBC with A/C, Power Steering and a Be Cool Radiator Kit.. Im not to sure on how much lighter that is then a stock BBC.. Any help would be great..

[exwestracer]

The aluminum heads are worth roughly 80lbs. IIRC.

To find the spring rate:
If possible, measure the distance from your lower shock mount shaft to the top of the coil spring at ride height. If you know anyone with scales, weigh the front end of the car. Don't worry if the front corner weights aren't the same, just divide the total by 2. Let's say it's 1000lb on each corner... You'll want the coil perches a minimum of 1" above the bottom of the threads on the (QA1) shock (adding the thickness of the perch and the locknut, you'll barely have any threads left on the bottom).

If you have the measurement from the shock mount shaft to the top of the spring from your car, you can subtract the coilover mount shaft to perch height. QA1 has engineering drawings of their shocks on their website, otherwise you'll have to call to get that dimension. What's left is the available length for the coil spring at ride height. The only other bit of info you'll need is the "free" length of the QA1 spring. Again, assuming you have 8" of avail. spring length, and the free length of their spring is 10", you need a spring that will compress 2" at 1000lb load, or a 500lb/in spring. DO NOT USE THIS NUMBER... It's just to show the process for determining rate.

That would be the stiffest spring you could use at that weight and ride height without cutting coils.

[Throttle]

I dont have any of the old front suspension and I dont have a scale to weight it with.. :(

[exwestracer]

I dont have any of the old front suspension and I dont have a scale to weight it with.. :(

Well, ask around or see if you can find an old road test for a big block second gen that has curb weight and F/R weight distribution. Even a Pontiac 455 will get you in the ballpark...

Say the curb weight is 3200lb, and the F/R is 55/45. Your front axle weight would be 3200 X .55 or 1760lb. Divide that by 2 and your corner weight is 880. That's prob not too far off, but go through the steps anyway...
https://static1.pt-content.com/images/pt/2010/07/halgmp35503_w-1.jpg
Now, you will STILL need to know how much installed height you have for the springs. You can measure this, but you need to have one lower control arm. Find one somewhere... Set the LCA level between the bolt holes in the frame and the bottom lip of the hole where the balljoint presses in. Measure from the shock mounts in the spring bucket up to the spring pad in the frame. Subtract about 3" (a guess, looking at the shocks in the ad) for the distance up to the lower spring perch on the shock.

So let's say you had 11" from LCA shock mount to upper spring pad... Minus 3" gives you 8" spring installed height. Then go back to the free length and rate as I posted previously.

[David Pozzi]

http://www.summitracing.com/parts/HAL-GMP3550-3/


Im been sitting here dreading the day Im going to have to put the Hotchkis Springs up front and knowing im not going to like them, so I decided that Im just going to put the Coilover setup in there that fits to my Lower Control Arm and Upper Spring Area..

Question is, are they worth doing?? I mean I know I can get the height I want out of them, but are they a good product to use under a car that will see a little bit of track time but more street time.. Im not sure what I need spring rate wise, I have a Aluminum Headed BBC with A/C, Power Steering and a Be Cool Radiator Kit.. Im not to sure on how much lighter that is then a stock BBC.. Any help would be great..

exwestracer's comments don't mention the spring moves around 50% of what the wheel moves. You can't use the load at the wheels to calculate coil compression without considering spring motion ratios.

I scaled a friends 67 BB camaro with 4 speed, PS, iron heads and no AC. It weighed 3520. A total front weight of 1920 to 1950 should be pretty close to what you have with your 2nd gen.

As you lower the car, you need to go stiffer rate. I wouldn't try lower than 450 lbs and at 450 I'd want to be near stock height. You run into the bumpstops pretty easily on a 2nd gen and it's not good if you start trimming them down. I think the Hotchkis coils are 600 to 700 rate and put the ride height about as low as is practical. If your tires and wheels are not that wide, you can get away with a softer spring package.
David

[Throttle]

Thanks for the info everyone.. I think I have an idea for what I need.

[Throttle]

http://www.summitracing.com/parts/HAL-GMP3550-3/

[Throttle]

We got tired of trying to guess, we went out and bought a scale..