72 with a/c coil spring replacement

[Michael B.]

Re: 72 with a/c coil spring replacement

Ed,

I haven't removed the springs yet. When I discovered the spacers yesterday I just assumed the springs were shot.

[Michael B.]

Re: 72 with a/c coil spring replacement

This is an update to the original post. I finally removed the springs today and was very surprised to discover they were actually 15 1/2 inches in height, with an addition 1 inch spacer below. There's no telling what spring "Bubba" installed in this car but it definitely wasn't the correct one. I've decided to try the springs from Zip. They advertise them as exact reproductions of the 331316 spring that replaced the 3931823 original spring for a small block, no a/c car. Although they say they are exact reproductions, the spring rate is 430 lbs. which is substantially heavier than the 1823 spring. This spring appears to be the closest to original equipment that's currently available.

Attached are a couple of photos of the old spring and spacer.

Mike

[Joe L.]

Re: 72 with a/c coil spring replacement

Mike, I understand now. I just did some searching and found no 3931824 springs anywhere, not even used. It may be that a prior owner added the spacers simply as a precaution thinking the springs may have sagged over the years. Maybe they're not necessary. It's entirely possible yours are good. But make sure before you consider using them that they are originals. Are there ID tags still there? Maybe they're old non-GM service replacements.

I would take some measurements, coil wire diameter, overall length, etc and find the spec for 3931824 to verify what you have, including a spring rate test if you can get that done locally. If they are proven original, you may want to consider using them after restoring and cleaning. If they're badly pitted or out of spec, time for more ideas. Yes you could go for the Eaton replacements, and you may have to, but you may have cut them so you don't end up too high.

Joe Lucia may have a NOS set in his "unavailable-for-sale-stockroom" for spec and measurement comparison. Joe has a 30,000+ parts collection in his NOS parts museum and is a great resource for information. If he sees this and has some info to share he'll likely respond.

Rich

Rich------


Unfortunately, I do not have an example of the GM #3931824 spring. It's one of the few spring part numbers that I do not have (yet).

[Joe L.]

Re: 72 with a/c coil spring replacement

This is an update to the original post. I finally removed the springs today and was very surprised to discover they were actually 15 1/2 inches in height, with an addition 1 inch spacer below. There's no telling what spring "Bubba" installed in this car but it definitely wasn't the correct one. I've decided to try the springs from Zip. They advertise them as exact reproductions of the 331316 spring that replaced the 3931823 original spring for a small block, no a/c car. Although they say they are exact reproductions, the spring rate is 430 lbs. which is substantially heavier than the 1823 spring. This spring appears to be the closest to original equipment that's currently available.

Attached are a couple of photos of the old spring and spacer.

Mike

Mike-----


This spring could be an original 3931824. At least, it has 10 coils like an original 3931824.

[Bob W.]

Re: 72 with a/c coil spring replacement

Mike Check on Rockauto for the specs of Moog springs as some vendors maybe selling reboxed Moogs.

Bob

[Joe L.]

Re: 72 with a/c coil spring replacement

There doesn't seem to be any decent choice for replacement front springs for my 72.

I spoke with Eaton Spring today. They show their MC 1400 spring to be the replacement spring for 72 small block cars with, or without air conditioning. It's an inch taller than the original spring and has a spring rate of 500 pounds. When I told him the specs on the 3931824 factory spring were 12.08 inches tall, with a spring rate of 264 pounds he said he didn't believe it and I must be mistaken. He admitted he did not have the data for this spring in any of his cross reference material.

On to Corvette Central. They show item 572052 as their replacement spring for a small block with air conditioning. However, this "stock" spring has a spring rate of 474 pounds. When you look at their Gran Touring spring the description says it's heavier than the standard spring which they say should have a spring rate of 294 pounds (not the 474 lbs. they sell).
The fellow at CC said he didn't have anything lighter than the Gran Touring spring which is advertised as heavier than standard.

On to ZIP. Zip sells item SU1022 which they describe as an "exact reproduction" of GM 331316. It's got the right dimensions but the spring rate is 430 pounds. GM 331316 replaced spring 3931823 which had a spring rate of 250 pounds.

It seems all the replacement springs are substantially stiffer than originals. I'm wondering if there would be a change in ride height with the ZIP spring? Also, how much would the ride and handling be affected with a 430 lb. spring as opposed to the 264 lb. original?

I'd really appreciate hearing from anyone who has installed any of these springs.

Thanks,

Mike

Mike------


Eaton is supposed to be the "GM Reproduction Parts Program" licensee for just about all Corvette springs. As such, they should have the GM blueprints and specifications for all. However, every time I have spoken with them, they seemed to be totally clueless as to spring specs. This has shaken my faith in them. The fact that they are, basically, selling a "few sizes fits all" sort of thing shows how the "GM Reproduction Parts" assurance that parts sold through the program are true reproductions is meaningless. Eaton is not the only example of this, though.

I think that the GM #331316 would work fine for you. Whether the ZIP spring is "an exact reproduction" of the 331316 is another matter. I've just seen too many "exact reproductions" that weren't.

[Michael B.]

Re: 72 with a/c coil spring replacement

Joe,

I spoke with Eaton in my initial search. They said they had the correct replacement spring for my car but when I inquired about the spring rate he admitted it was 550 pounds. I told him the original 3931824 spring had a SR of 264 pounds and he said he didn't believe that, and I must be mistaken. I asked him to look up the specs and he admitted he didn't have that spring in his data base. I wasn't impressed.

I can't find my notes that have the 3931824 specs. but I was under the impression the original spring was just a bit over 12 inches in height. When I saw the springs I removed were 15.5 inches I just assumed they were replacements.

Mike

[Joe L.]

Re: 72 with a/c coil spring replacement

Joe,

I spoke with Eaton in my initial search. They said they had the correct replacement spring for my car but when I inquired about the spring rate he admitted it was 550 pounds. I told him the original 3931824 spring had a SR of 264 pounds and he said he didn't believe that, and I must be mistaken. I asked him to look up the specs and he admitted he didn't have that spring in his data base. I wasn't impressed.

I can't find my notes that have the 3931824 specs. but I was under the impression the original spring was just a bit over 12 inches in height. When I saw the springs I removed were 15.5 inches I just assumed they were replacements.

Mike

Mike------


Well, I was wrong. I DO have some NOS GM #3931824 springs [none for sale]. These springs are 15-7/8" in overall length with a wire OD of 0.615" and 10 coils (as I mentioned previously). They are dual rate type springs (as are most 64-82 springs). Pictured below:

[Richard M.]

Re: 72 with a/c coil spring replacement

This is an update to the original post. I finally removed the springs today and was very surprised to discover they were actually 15 1/2 inches in height, with an addition 1 inch spacer below. There's no telling what spring "Bubba" installed in this car but it definitely wasn't the correct one. I've decided to try the springs from Zip. They advertise them as exact reproductions of the 331316 spring that replaced the 3931823 original spring for a small block, no a/c car. Although they say they are exact reproductions, the spring rate is 430 lbs. which is substantially heavier than the 1823 spring. This spring appears to be the closest to original equipment that's currently available.

Attached are a couple of photos of the old spring and spacer.

Mike

Mike, Zip, and likely others, have been misinformed. Vendors advertise them that way because that's what they've been told.

I strongly feel those reproduction Eatons will result in a suspension at least 1" too high, and you'll have to do what I did in post#7. It may appear you have original springs based on the comparison with Joe's help. If I were you I would clean and reuse those springs.

Mike------

Eaton is supposed to be the "GM Reproduction Parts Program" licensee for just about all Corvette springs. As such, they should have the GM blueprints and specifications for all. However, every time I have spoken with them, they seemed to be totally clueless as to spring specs. This has shaken my faith in them. The fact that they are, basically, selling a "few sizes fits all" sort of thing shows how the "GM Reproduction Parts" assurance that parts sold through the program are true reproductions is meaningless. Eaton is not the only example of this, though.

I think that the GM #331316 would work fine for you. Whether the ZIP spring is "an exact reproduction" of the 331316 is another matter. I've just seen too many "exact reproductions" that weren't.

Joe, Add me as a user of Eaton "exact replacements"......that weren't. Very frustrating.

Hmmm, Back in a earlier post I figured you had some NOS 3931824 springs for Mike to compare to, then you said you didn't have any, but I couldn't believe it. I just knew you had some back there somewhere.

Rich

[Michael B.]

Re: 72 with a/c coil spring replacement

Rich,

Thanks for your input and sharing your experience with these "reproduction" springs. I don't want to ever have to remove those springs again after restoration just to adjust the ride height. Additionally, not having much experience with breaking loose ball joints I seem to destroy the boot in the process more times than not.

I need to do more research before deciding how to proceed. It seems ridiculous to me that GM distinguished between a/c and non a/c cars using original springs that only had a 14 pound difference, but all the replacement springs offered are at least an additional couple hundred pounds heavier. I'm also surprised the additional 200 pounds of spring rate doesn't raise the cars so high that buyers are screaming about it.

Mike

[Richard M.]

Re: 72 with a/c coil spring replacement

Rich,

Thanks for your input and sharing your experience with these "reproduction" springs. I don't want to ever have to remove those springs again after restoration just to adjust the ride height. Additionally, not having much experience with breaking loose ball joints I seem to destroy the boot in the process more times than not.

I need to do more research before deciding how to proceed. It seems ridiculous to me that GM distinguished between a/c and non a/c cars using original springs that only had a 14 pound difference, but all the replacement springs offered are at least an additional couple hundred pounds heavier. I'm also surprised the additional 200 pounds of spring rate doesn't raise the cars so high that buyers are screaming about it.

Mike

Many, and myself have complained yet were obviously ignored. Likely a case of depleting stock... at the expense of the wizz-wheelers.

[Joe L.]

Re: 72 with a/c coil spring replacement

Hmmm, Back in a earlier post I figured you had some NOS 3931824 springs for Mike to compare to, then you said you didn't have any, but I couldn't believe it. I just knew you had some back there somewhere.

Rich

Rich-------

Yes, I went back and checked my "secondary" inventory list and found that I did have the springs. The hard part was digging them out. I almost wished I didn't have them; tote bins full of coil springs are HEAVY. However, there are a few 1964-74 Corvette coil springs that I do not have NOS examples of (yet).

[Joe L.]

Re: 72 with a/c coil spring replacement

Rich,

Thanks for your input and sharing your experience with these "reproduction" springs. I don't want to ever have to remove those springs again after restoration just to adjust the ride height. Additionally, not having much experience with breaking loose ball joints I seem to destroy the boot in the process more times than not.

I need to do more research before deciding how to proceed. It seems ridiculous to me that GM distinguished between a/c and non a/c cars using original springs that only had a 14 pound difference, but all the replacement springs offered are at least an additional couple hundred pounds heavier. I'm also surprised the additional 200 pounds of spring rate doesn't raise the cars so high that buyers are screaming about it.

Mike

Mike------

I agree with Rich that your springs look to be re-usable. They do not appear to suffer from any significant corrosion damage. Such damage is the "killer" of springs. Plus, their free length appears to be near original.

Now, the real quandary is the spacers. I think there's a very good chance that they are original to the car. Dr. Rebuild has, or at least used to have, OEM examples of these spacers for sale.

[Michael B.]

Re: 72 with a/c coil spring replacement

Joe,

If you really wish you didn't have those springs, I can help you out.

Mike

[Edward J.]

Re: 72 with a/c coil spring replacement

Mike, When I restored my 72 air coupe there were no spacers, but have heard it said here before someone makes them. Do you have any pic.s of the car before resto?? My say is as I said in prev. post if they measure up to be the same re-use them and install the spacers back in. being around cars my whole life, spring engineering is a science for all cars for ride height, handling, and comfort. I think anything other than a O/E spring will give up all the above. springs may have settled over the years as most do 3/8 in. is not much.