[kdeman1@yahoo.com]

Spring recommendation for stock ride height?

When I bought my project T/A the last thing I expected was a high ride height. However here I am sitting 10.5 in off the ground in the front!

Anyone have a recommendation for stock ride height springs?

[78w72]

Is that with an engine? if not it will come down a lot when the engine/trans is installed, if so, someone used the wrong springs and tightened everything while it was on jack stands.

Try to loosen all control arm and leaf spring bushing bolts then re tighten with full vehicle weight on them. Can also cut the front springs about 1 full coil if on a budget. for a nice ride height about 1-1.5" lower than stock, PTFB has good spring and suspension parts for these cars.

[kdeman1@yahoo.com]

Yep! That’s loaded with an engine and trans.

Looks off to you also I assume?? I did try and loosen all control arm bolts, and “bounce” the car to see if I’d have any luck lowering her.

No luck!

[78w72]

Yeah it looks way off front & rear, like a 4x4, the wrong springs were used which is pretty common on these cars.

Front springs from auto parts stores are usually way too tall, many time the same spring is used for numerous cars, back when I restored my 78 T/A I called around and was given a moog part# for the fronts that was the same spring for other cars and even the same cars with different engines. I went with a #5006 moog spring up front that was listed as correct, it sat way too high, almost like yours. The easy fix was to cut 1 full coil off the top of the spring, that is equal to about 1" off the free standing height of the spring which equals about a 2" drop on the car. The amount you cut off the spring will double the drop of the car when measured from the ground to center of fender wheel well. Car still rides nice but has a slight increase in spring pressure and plenty of suspension travel for street use.

The rear leafs were probably the cheap heavy duty 5 leafs, stock were 4 leafs im pretty sure, shop around for a stock replacement that is 4 leaf and stock height, or better yet get the PTFB dropped leafs.

Besides stock, the other option is buying springs from aftermarket places or direct from a spring manufacturer that can get closer to stock ride height but usually more expensive than "dropped" springs from places like PTFB etc. PTFB is the best value on springs & other parts IMO, I use their full GT kit on a 72 firebird, they are about 1-1.5" drop and looks great with stock 15" wheels/tires, the car rides & handles very good. They sell rear leafs that are almost like stock height too.

Check out their website for more info or consider cutting your current front springs and look into lowering blocks for the rears.

[srmmmm]

Here's pictures without the drivetrain and with drivetrain. The front springs were ones I have put in my original car that I picked up from the GM Parts Division in FLint, Mi in college. They were listed for a 76, 400 w/AC, Cruise Control, and the WS6 handling option. This was supposedly the highest front end weight of any F-bodies and the stiffest springs when I bought them in 77.

Poly bushings were installed as part of the restoration. Do they need to go through the same pre-loading as regular rubber bushings???

It's definitely sitting higher than the original car was, but I imagine it will drop another inch or so when the exhaust, glass, spare tire, fuel and interior is added.

[78w72]

Originally Posted by srmmmm

Here's pictures without the drivetrain and with drivetrain. The front springs were ones I have put in my original car that I picked up from the GM Parts Division in FLint, Mi in college. They were listed for a 76, 400 w/AC, Cruise Control, and the WS6 handling option. This was supposedly the highest front end weight of any F-bodies and the stiffest springs when I bought them in 77.

Poly bushings were installed as part of the restoration. Do they need to go through the same pre-loading as regular rubber bushings???

It's definitely sitting higher than the original car was, but I imagine it will drop another inch or so when the exhaust, glass, spare tire, fuel and interior is added.

Nice car! But that sits way too high also. Not sure why a CC option would matter for springs, theres no additional weight that would be a factor. Your in the same boat as the OP as far as options to lower the car, if you want to keep the front springs there is no harm in cutting 3/4-1 full coil off the top, will still ride like stock springs with ~10% added stiffness over stock springs.

All moving suspension bushings need to be torqued to spec with the full weight of the car on the ground, either up on a lift or all 4 wheels under load on jack stands or ramps. I use ramps under the front tires & jack stands out near the ends of the rear axles to put full weight and provide clearance for getting under it to tighten bolts. Be sure to fully lube the poly bushings & shells with the provided grease.

Heres a couple pics to show the ride height after cutting stock replacement springs on the 78 and the PTFB GT springs on the 72. 78 has 255/60 front & 275/60 rear, 72 has 225/70 all around that are stock size for mid-late year 2nd gen firebirds. 72 has been re-painted since this pic.

[jhein]

This is my car with Eaton Detroit springs. Standard height front and rear. The car had worn out springs and was sitting too low. These raise the front 2 inches and the back 1 inch.

[srmmmm]

Originally Posted by 78w72

All moving suspension bushings need to be torqued to spec with the full weight of the car on the ground, either up on a lift or all 4 wheels under load on jack stands or ramps. Be sure to fully lube the poly bushings & shells with the provided grease.

Appreciate the tip! I am sure nothing's been torqued yet with full weight so I'll make sure that is done. Yours look fantastic though!

[srmmmm]

Originally Posted by jhein

This is my car with Eaton Detroit springs. Standard height front and rear. The car had worn out springs and was sitting too low. These raise the front 2 inches and the back 1 inch.

That's right where my height was at prior to the restoration, so I'm pretty sure mine just needs to be finished out and all the bushings re-torqued. Your engine sounds great and is a nice comparison against my 413 (stroked 350) with the XE276HR cam: 234/230@.050 .502/.510 and 110LSA Idle speed 800rpm.

https://www.youtube.com/watch?v=nxDtH_76piU

[Steve C.]

A tid bit for interest. Here are the dimensions from the AMA Specifications for a 1970 2nd Gen ride height. These are height dimensions from the rocker panel to the ground in two places. The forward point on the rocker panel is located 36.3 inches from the front wheel centerline and it is supposed to be 6.5 inches off the ground. The rear point is 16.1 inches from the rear wheel centerline and is supposed to be 5.5 inches off the ground. Keep in mind that this is supposed to be the factory ride height and I think they they were a little nose high... at least that's the general opinion I have of most Birds.



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[Formulas]

I could never stand the stock nose high on these cars... level or a touch lower in front ...

when its time to cut a spring, do it with a cut off wheel no torch

[HWYSTR455]

Originally Posted by 78w72

All moving suspension bushings need to be torqued to spec with the full weight of the car on the ground, either up on a lift or all 4 wheels under load on jack stands or ramps. .

This is not true, only OE bushings with the 'teeth' on the center sleeve need to be at ride height when tightened. All other bushings will articulate freely.

The only exception MIGHT be when it comes to the leafs, but 'it depends'. I don't think you can tighten the shackle bolts tight enough to prevent rotation of the sleeve but it MIGHT be possible.

It won't matter how tight you make upper & lower control arm bushings, the sleeve rotates inside the bushing (poly). That's what the lube it for, as well as the faces of the bushing where it meets the frame.

Solid or del-alum bushings freely rotate no matter.

In both those cases, the inner bushing sleeve is longer so you can't over tighten it.


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[JLMounce]

Originally Posted by Steve C.

A tid bit for interest. Here are the dimensions from the AMA Specifications for a 1970 2nd Gen ride height. These are height dimensions from the rocker panel to the ground in two places. The forward point on the rocker panel is located 36.3 inches from the front wheel centerline and it is supposed to be 6.5 inches off the ground. The rear point is 16.1 inches from the rear wheel centerline and is supposed to be 5.5 inches off the ground. Keep in mind that this is supposed to be the factory ride height and I think they they were a little nose high... at least that's the general opinion I have of most Birds.



.

Pontiac specifically was messing around with getting the back end down. You can see this prominently with the dimpled axle housings in the 69 Firebird.

The F-Body's were some of the first cars to undergo any kind of wind tunnel or drag analysis. Getting the butt down, gets the windshield out of the air a bit and helps with the car's drag co-efficient and frontal area.

On the springs, part of the issue is that different part numbers have been homologated together. Depending on options, the factory may have used several different spring free lengths to achieve the correct ride height. To the consumer 50 years later, there's only really one or two available and it may or may not be right for the car.

What I've been suggesting to people that want a near stock ride height is to look at aftermarket springs that are designed around a 1" lowering. That will usually put the car at a height that is acceptable for stock appearing once you've added new bushings etc. You can also add some spring spacers as needed if it needs to go up by half an inch or so.

[jhein]

Originally Posted by JLMounce

Pontiac specifically was messing around with getting the back end down. You can see this prominently with the dimpled axle housings in the 69 Firebird.

The F-Body's were some of the first cars to undergo any kind of wind tunnel or drag analysis. Getting the butt down, gets the windshield out of the air a bit and helps with the car's drag co-efficient and frontal area.

On the springs, part of the issue is that different part numbers have been homologated together. Depending on options, the factory may have used several different spring free lengths to achieve the correct ride height. To the consumer 50 years later, there's only really one or two available and it may or may not be right for the car.

What I've been suggesting to people that want a near stock ride height is to look at aftermarket springs that are designed around a 1" lowering. That will usually put the car at a height that is acceptable for stock appearing once you've added new bushings etc. You can also add some spring spacers as needed if it needs to go up by half an inch or so.

That's what I liked about Eaton Detroit Spring. For Gen 2 F body they offer 4 different front coils. With and without AC and two different ranges of production dates. Then they also offer each of those in 7 different ride heights from -2 to +2 inches.

[HWYSTR455]

Eaton may list multiple springs, and drop/rise, but no where do they list rates. So you have no idea what you're getting.

Keep in mind, the industry standard is like 10% +- tolerance.


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[HWYSTR455]

https://www.thespringstore.com/stand...tolerance.html

"The tolerance for standard spring rate used in the industry is of plus or minus ten percent (+/– 10%). "

And that's why so many have issues with ride height or 'lean'.

You have to choose a manufacturer that has better tolerance, like one that lists <5%.

If they don't list it, it's +-10% or more.

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