Spring rating fron/rear ls1 equiped Firebird 2 gen

[Formula 400]

Hi!

I'm going to upgrade my suspension and add a lot of chassi stuff to make the car chassi stiffer.

Replacing the frame bushings with solid ones and adding frame extensions and firewall braces.

I'm thinking of running 1200lbs front springs and was wondering what would be the matching rear leaf spring rating?

I want the car to handle better than a Porsche or a Ferrari but it'll mostly be used on the street as a daily driver during summer season. Might be upgrading to a LSX block sometime in the future.. Any ides or thoughts? Something I'm overlooking?

Thanks before hand.
Formula

[amargari]

Isn't 1200 lbs a little high for a street driven 2nd gen? I thought competition springs were around 650 lbs.

[claytonisbob]

Stiff springs != good handling. That's way too high of a spring rate for anything on the street. Expecting Ferrari level handling from a muscle car isn't going to happen with a couple $k of springs, bushings, shocks and control arms. Actually, making that happen is damn near impossible lol. There are Pro-Touring cars that can do it, but we're talking the creme a la creme. And even then, they become more racecar like than streetcar. Think refinement.

BTW, the LSX block is even heavier than the iron 6.0L blocks. In the interest of handling, LS2, LS3, LS7 & blocks are the way to go. I kinda see the LSX block as mostly a drag racing only block. It's a great basis to build an engine if you're planning on making 1000+ hp on boost.

Aside from that, welcome to the forum man. Do some reading! There is a lot of info on F-Bodies on here. Check out Mary Pozzi's newly built second gen in the Projects forum.

[monteboy84]

1200 is WAY too stiff. I wouldn't go more than 800, and even that is pretty stiff.

-matt

[formula]

Heyyyyyy another formula! Welcome aboard!

1200lb front springs is like psycho stiff. To think about it simplistically--you're going to have to load 1200 lbs of force onto one spring to get 1 inch of travel. Half of that should be PLENTY for a street car!

If you really want to outhandle a porsche or ferrari, you're going to end up working pretty hard. I have around 10k in my suspension and my father's bone stock 911 can still eat me up in the twisties--it's sheer physics. Gonna be tough to make a 3500 lb car move like a 3000 lb car no matter what you do--you've got two fat guys worth of extra mass moving around with you! Combine that with a 30-year old basic suspension configuration and it's a tough job. I would recommend looking at detroit speed's front subframe and rear suspension if you do decide to go that route. If, instead, you just want a very nice handling 2nd gen, there are tons of choices--Pro-touringf-body.com makes a great spring package, and that combined with savitske classic and customs' front package will get you a long way on a shorter dollar.

NOW--here's how I choose to pick off porsches--Get the suspension set up to where you can at least keep up with them in the twisties, and then lay down bloody murder on the straights. I assume you don't actually mean an LSX but instead an LSx, i.e ls1-9--I'm with you there, I'm running an L76 out of a G8 and with a cam swap I'm right at 500 hp/500 tq at the crank (420 at the wheels). Edelbrock makes a very nice kit to bolt LS engines into 2nd gens, it includes headers and engine mounts that work perfectly together.

Here's a quick shot of how mine sits with the edelbrock stuff--you'll have to forgive the photo quality, it's the quickest one I could grab that shows how it sits in the engine bay.
https://static1.pt-content.com/images/pt/2011/01/DSC07808-1.jpg

I hope this helps--let me know if you need more help from there!

[demonpixel]

Hey man I'm really sorry to hijack your thread but I was just about to put up a VERY similar thread to yours so I hope you don't mind!

I finally finished swapping in the LS1 in my 72 Formula. It had a Pontiac 400 in it before, and everything was cast iron - intake, heads, block.

Now that everything is aluminum, the car sits soooo high that I think the springs are maxed out and the upper a-arms are at so much of an angle that my wheels have really bad toe out.

I don't know anything about suspension so I have a few newb questions -

1. Has anyone had this experience (replacing a heavier engine with a lighter one causing the front to sit so high)?

2. What did you have to do to remedy this? Did you end up getting different springs and upper and lower a-arms? The car is a street cruiser/daily driver, not an autocross car or drag car, if that makes a difference.

Thanks for any help/advice; I'm soooo close to getting this car the way I want it!

And here are a few pics of the project:

https://static1.pt-content.com/images/pt/2011/01/LS_firebird1-1.jpg

https://static1.pt-content.com/images/pt/2011/01/LS_firebird2-1.jpg

https://static1.pt-content.com/images/pt/2011/01/night_shot_firebird-1.jpg

https://static1.pt-content.com/images/pt/2011/01/LS_firebird3-1.jpg

https://static1.pt-content.com/images/pt/2011/01/LS_firebird4-1.jpg

https://static1.pt-content.com/images/pt/2011/01/LS_firebird5-1.jpg

[formula]

One thing to check before you swap anything--if you just installed those front springs, did you lock everything down with the weight of the car on the suspension or hanging in the air? If it was on the ground or if those are still the originals, then yeah sounds like a spring swap is in order for you as well--the a-arms should be fine once you get some springs designed for the lighter engine in there. Might as well replace the shocks at the same time and make sure that all of your bushings are in good shape. Same suggestion--check out PTFB (pro-touringf-body.com) or hotchkis, as both have kits ready to go for small block cars that should be a low enough spring rate and be a little shorter, the combination of the two being perfect to remedy your issue.

That carbed LS looks all business in there! way cool, man!

[demonpixel]

One thing to check before you swap anything--if you just installed those front springs, did you lock everything down with the weight of the car on the suspension or hanging in the air? If it was on the ground or if those are still the originals, then yeah sounds like a spring swap is in order for you as well--the a-arms should be fine once you get some springs designed for the lighter engine in there. Might as well replace the shocks at the same time and make sure that all of your bushings are in good shape. Same suggestion--check out PTFB (pro-touringf-body.com) or hotchkis, as both have kits ready to go for small block cars that should be a low enough spring rate and be a little shorter, the combination of the two being perfect to remedy your issue.

That carbed LS looks all business in there! way cool, man!

THANK YOU!! That was the response I was looking for. I'll hit up PTFB or Hotchkiss tomorrow and see if we can figure out what spring and bushings kit I need to get. A few people mentioned using v6 springs from a late 70s second gen fbody too if I'm on a budget. Any experience with those springs, Wes?

I love the look of the carbed LS1. But that's actually a Powerjection fuel injection system on top. :)

Your L76 looks so clean!!! Very nice work man. I've got a ways to go after my ziptied engine bay. lol

[formula]

Wow, I hadn't seen that powerjection setup yet--that looks exactly like the demon I had on my 350 before I swapped. Dang!

Using the v6 springs would be fine to good if you're planning to drag the car--but on a street car designed to corner well, I'd be concerned that the v6 springs would be too soft and would cause the car to wallow. See if you can get a spring rate on the v6s and compare it to the aftermarket stuff--if it's within, say, 25 lb/in you'd be good to go.

[demonpixel]

Wow, I hadn't seen that powerjection setup yet--that looks exactly like the demon I had on my 350 before I swapped.

I love this system, feels like the car is fuel injected...CUZ IT IS. Here are some pics if you're not familiar with it (when I bought it they called it the BossEFI system):

https://static1.pt-content.com/images/pt/2011/01/tb1-1.jpg

https://static1.pt-content.com/images/pt/2011/01/tb4-1.jpg

https://static1.pt-content.com/images/pt/2011/01/tb5FUELINJECTORS-1.jpg

https://static1.pt-content.com/images/pt/2011/01/tb6-1.jpg

https://static1.pt-content.com/images/pt/2011/01/ecm-1.jpg

And I have officially hijacked the OP's thread. Sorry man!

[Formula 400]

Heyyyyyy another formula! Welcome aboard!

1200lb front springs is like psycho stiff. To think about it simplistically--you're going to have to load 1200 lbs of force onto one spring to get 1 inch of travel. Half of that should be PLENTY for a street car!

If you really want to outhandle a porsche or ferrari, you're going to end up working pretty hard. I have around 10k in my suspension and my father's bone stock 911 can still eat me up in the twisties--it's sheer physics. Gonna be tough to make a 3500 lb car move like a 3000 lb car no matter what you do--you've got two fat guys worth of extra mass moving around with you! Combine that with a 30-year old basic suspension configuration and it's a tough job. I would recommend looking at detroit speed's front subframe and rear suspension if you do decide to go that route. If, instead, you just want a very nice handling 2nd gen, there are tons of choices--Pro-touringf-body.com makes a great spring package, and that combined with savitske classic and customs' front package will get you a long way on a shorter dollar.

NOW--here's how I choose to pick off porsches--Get the suspension set up to where you can at least keep up with them in the twisties, and then lay down bloody murder on the straights. I assume you don't actually mean an LSX but instead an LSx, i.e ls1-9--I'm with you there, I'm running an L76 out of a G8 and with a cam swap I'm right at 500 hp/500 tq at the crank (420 at the wheels). Edelbrock makes a very nice kit to bolt LS engines into 2nd gens, it includes headers and engine mounts that work perfectly together.

Here's a quick shot of how mine sits with the edelbrock stuff--you'll have to forgive the photo quality, it's the quickest one I could grab that shows how it sits in the engine bay.
https://static1.pt-content.com/images/pt/2011/01/DSC07808-1.jpg

I hope this helps--let me know if you need more help from there!


Thanks!

Well the aim is to outperforme a Porsche and if I only happen to get close hehehe so be it since it'll be much better than what it is now.. :D

A friend of mina has over 1800lbs/in on his Mercerdes 190E he uses for a track car so I though that about half of that would be good, going to put in pretty big wheels later and don't want to bottom out when I corner the car.

Been trying to talk to Dave at Pro-touringf-body.com but he seems busy and I've not gotten a response in 2 weeks I think, wanted to buy a "few" things from him including fron coils and rear leafs.

But if I go with 1200lbs/in front coils what would be a suitable match spring rating wise for the rear leafs?

//Formula. :D

[68sixspeed]

don't go 1200#, for one thing comparing from car to car is tough as there is a ratio on the spring rate depending on the spring location in/out on the lower control arm, etc. But for comparison I don't know anyone running over a 650# spring even with a big block. (I run 550#) Car weight, tires, too many variables... unless the benz weighed over 5000 pounds or had a 1:4 wheel rate to spring ratio it didn't need to have 1600# springs. I don't think we ever ran much over 1000# springs on a stock car, most of the time it was 600-800#'s up front and 250#'s in the rear. Stiffer is not always faster.

[LeighP]

Stiff springs on the street do not = great handling....what happens is street road surfaces suck compared to a track....disturbances in the surface of a corner (ripples, holes, cracks etc) will cause a really stiffly sprung car to bounce slightly, rather than letting the suspension compress and extend to match the road surface....if the car is loaded up in a corner when the wheels skip off the pavement, it'll swap ends.
I've found a slightly softer rate spring with very good shock absorbers and really large anti-roll bars is a better combination where you have to cope with real world road quality surfaces.
Tis is based on the original style coil/leaf musclecar systems....some of the modern suspension designs don't suffer from such limitations.

[Formula 400]

Hi 68sixspeed!

His car weighs less and we checked the spring location and it's around the same place on his as it is on mine. He did however do a very thorough work on the math required to get the springs just right for what he wanted from it. I thought I could cheat a bit and use about half since his spring location is around the same place as min and my ambitions on the track is not the same.

Road quality in Sweden is pretty good but on the other hand I don't know the road quality over there... ;)

But a 800libs/in spring up front would mate well with a 250lbs/in at the rear? If I understood your post. (Well around there since you said 600-800). so IF and I say IF since I've not decided yet a 1200 front spring would mate well with a 375 libs/in rear leaf? Would like to se a few youtube vids from peps in here on the track where the Spring rating is known.... Just to see how much the car leans in the corners.

Again thanks for the input!
Formula

[Formula 400]

Stiff springs on the street do not = great handling....what happens is street road surfaces suck compared to a track....disturbances in the surface of a corner (ripples, holes, cracks etc) will cause a really stiffly sprung car to bounce slightly, rather than letting the suspension compress and extend to match the road surface....if the car is loaded up in a corner when the wheels skip off the pavement, it'll swap ends.
I've found a slightly softer rate spring with very good shock absorbers and really large anti-roll bars is a better combination where you have to cope with real world road quality surfaces.
Tis is based on the original style coil/leaf musclecar systems....some of the modern suspension designs don't suffer from such limitations.

Hi!

The roads in Sweden isn't half bad at times so I'm not too worried about the street, And wheel hope due to a very stiff spring isn't it possible to remove that with a properly matched shock absorber? or as my friend said harmonic dampener. With the ****ty springs I've got now it's a pain in the a**... 9½ rings on my current coil springs which was said to be heavy duty makes the car bottom out at 130km/h on the highway cause it's a slight "valley" lack of a better word... (130km/h should be around what 60-70Miles/hour?)

Wonder if the Pozzi's would give their info on what they use on their 2 gen beast... ;)

//Formula

[formula]

The pozzis are using hotchkis springs, right in the 800 lb range on the front. If you want something a little more aggressive than that I believe DSE's are a little higher but don't quote me on that.

100km is 62 miles.

As you've started to touch on, it sounds like better shocks might be in order along with springs. It sounds like you're using cut stock springs now? For all intents and purposes springs only help during compression, if you're having issues with overextension your shocks are underdamped or too short.

Regardless, here's the issue with too much spring--overly high spring rates can actually hinder handling by preventing weight transfer as the car turns, underloading the tires and thus limiting their effectiveness. Going with one of the matched kits from ptfb, dse or hotchkis ensures that excessive body roll is eliminated without hindering proper weight transfer.

I'm sorry if this seems off base, I'm reading from my phone so the tiny screen may hinder my comprehension.

[Formula 400]

The pozzis are using hotchkis springs, right in the 800 lb range on the front. If you want something a little more aggressive than that I believe DSE's are a little higher but don't quote me on that.

100km is 62 miles.

As you've started to touch on, it sounds like better shocks might be in order along with springs. It sounds like you're using cut stock springs now? For all intents and purposes springs only help during compression, if you're having issues with overextension your shocks are underdamped or too short.

Regardless, here's the issue with too much spring--overly high spring rates can actually hinder handling by preventing weight transfer as the car turns, underloading the tires and thus limiting their effectiveness. Going with one of the matched kits from ptfb, dse or hotchkis ensures that excessive body roll is eliminated without hindering proper weight transfer.

I'm sorry if this seems off base, I'm reading from my phone so the tiny screen may hinder my comprehension.

Hi!

Well yea the shock and the spring coexist and if one is not matched properly it will affect the performance in a negative way. If my understanding is correct is the spring rating is simply how much it takes to compress the spring a given distance. So keeping that in mind I believe that the weight force of the car, when you drive it on the highway for example, should be compensated by a matching spring and to keep the car in the smooth spot concerning suspension geometry while the shock should eliminate the harmonic in the suspension. (Maybe not the best word or sentence to describe it...) The faster you go the more weight force there will be and the stiffer the spring to compensate?

But in short.. my belief is that the stiffer the springs the softer the shocks... to an extent of course.

Again I'm as far from an expert on the subject as one could get but I like to understand how things work and to get it right the first time more or less.

Thanks for the tips on purchase locations... :D

//Formula

[formula]

The shock to spring relationship is a lot more complex than that--the shock is designed to eliminate the repeat oscillations that occur in a spring when it is compressed by an impulse force I.e. A bump.

I found this article, it may help--or searching for a Swedish equivalent may be wise, as it involves some pretty technical language.

http://mathinsite.bmth.ac.uk/pdf/msdtheory.pdf

[68sixspeed]

ok, lets back up a bit... what is the car weight? (total and front/rear balance) what kind of tires? (tread width, tire type) Without slicks I can't see having the capability of putting the load on the car to need that heavy of a spring. Are you changing the suspension geometry? (roll center location comes to mind) If you over-spring the car, it will basically bounce all over the place on anything short of a smooth race track and the car is likely going to push like a pickup truck going into the corner. Sorry for so many questions, just trying to help. -Dan