Coil spring specs.

**iceman** · 07-09-2014, 02:32 PM

Hello All:
This is my first time posting here so bare with me. I'm looking to replace the rear coil springs on my 1967 GS-340. I've owned the car from new, did a lengthily restoration (26 yrs. ) re-registered in 2005 and have been driving it since. Over the years during restoration, springs got mixed, switched and unidentified from my originals to ones from parts cars. Needless to say I used the best ones I could find among the ones I had. The car rides good handles good but sags when the trunk gets loaded with suitcases, chairs, tools, BEER, etc. going to shows. I want to upgrade the springs in the rear but I'm undecided what to use. The '67 parts book I have lists the standard spring as #9778686. An option for the 43417 (GS-340) was a "Sport Pkg." or "Ralley Road Package" code H4 which consisted of special heavy duty springs, and rear stabilizer bar. That option did not come on mine so I assume originally had just the standard #9778686 springs. I've tried to locate a part number for the springs used in the "sport Pac" but all I can come up with off an old options sheet is code NZ.
Does anyone out there have any kind of specifications on either of these springs, like wire diameter, design load, load rate, free height, etc. If I had a starting point, maybe I could make an educated guess on what to switch to. I'd hate to buy new springs only to find there not much better than what I have now or find that they are too stiff. I did read somewhere that the variable rate springs affect handling and in not a good way.
Any information would be greatly appreciated. Sorry I was so long winded.
Tom

**bob k. mando** · 07-09-2014, 05:50 PM

here's the 67 Chassis Manual
http://www.teambuick.com/reference/l...ssis/index.php

i don't know your original spring specs but if LOADED ride height is your primary concern you may want to consider installing air bags in the rear.

amusingly, the bigger cars in 67 actually had 'Automatic Level Control', which sounds exactly like what you're looking for.
http://www.teambuick.com/reference/l...files/40-b.php

**bob k. mando** · 07-09-2014, 05:52 PM

something else you can do is install spring shims. these effectively increase the rate of the spring and could give you an idea of how much stronger of a spring you're looking for.

anybody running a circle track late model should have a spring rate tester, if you're looking to spec out what you have right now.

**Bob** · 07-09-2014, 08:39 PM

I have a '67 GS400, and had a low back end. I solved it by simply adding some 2" spacers which I think left the car sitting just about right.

**iceman** · 07-14-2014, 02:16 PM

I'd rather not add anything that would show physically. I was once told to install station wagon springs as they were heavier duty but right now I'm still gathering what little information I can. Thanks for the responses so far.

**telriv** · 07-14-2014, 08:03 PM

Install a 1" spacer on the top of the springs & NO ONE but you will know they are there as they can't be seen unless you look crawl/under the car.

**iceman** · 07-15-2014, 09:16 AM

What do you use as spacers? Rubber, steel or can they be purchased at local auto parts suppliers in varrious thicknesses and added or subtracted as needed. Is there a difference between a shim and a spacer as suggested in other posts? Keep in mind that my existing springs are 47 years old and probably pooped out by now. I'm leaning more toward replacing them than just adding spacers. I'm sure spacers will improve the height but what will happen when extra weight is introduced to either the back seat, trunk or both using my old springs?
Tom

**bob k. mando** · 07-16-2014, 08:50 PM

<i>but what will happen when extra weight is introduced to either the back seat, trunk or both using my old springs?</i>

a spring spacer does not change spring rate at all. so if your current springs compress 1/2" when 500lbs ( for instance ) are added to the trunk, they will STILL compress 1/2" when you add 500lbs ( or 1" for 1000lbs, etc ) to the trunk. you're just starting with an extra 2" ( or whatever ) of height. this is what "spring rate" means == lbs of load necessary to produce 1" of compression.

when springs are truly 'shot', they'll compress to the point where the coils start touching each other, top to bottom ( you'll see evidence of this as shiny areas on the top and bottom of the coils ). as coils contact each other ( coil bind ) the effective spring rate spikes up because it's producing the same effect as a shim but only momentarily. you're effectively removing coils from the spring. this can cause handling problems if you actually have this issue.

**Bob** · 07-17-2014, 07:33 AM

BTW when installing spring spacers, you may need a longer shock depending on the travel restrictions of the ones on the car.

**iceman** · 07-17-2014, 08:20 AM

Thanks Bob.
I recently found the ride height that I'm suppose to have with a full tank of gas. It's suppose to be 9-1/2" from the floor to the bottom of the rockers. Mine measure 8-1/8" on one side and 8" on the other. Given a flaw in the floor, the car sits 1-1/2" low. I'm assuming the springs are just fatigued with age. Contrary to my earlier post I believe these springs are my correct originals. This is why I'd like to find the specs on what they should be as this would give me a good starting point. A standard GS-400 takes a different spring than a GS-340. Would they work, maybe but who can say for sure. I'm probably over thinking this whole spring issue, but I don't want to install something that gives too harsh a ride or will sink to low when the trunk is loaded.
Tom