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Old 02-21-2013, 12:52 PM   #1
Mattydale
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Modified Coil Springs

Just removed the original coil springs (tag HV 3931826) and they are different lengths. Never saw a Corvette front end with 3 coil springs.

http://i47.tinypic.com/2pte5o0.jpg

This explains why the car sat lower on the drivers side. And I thought I only needed to lose a few pounds.
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Old 02-21-2013, 01:17 PM   #2
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Looks like it broke. Time for new ones.

Nice thing is front coils can be bought new very inexpensively.
On sale right now.

http://www.vbandp.com/C2-C3-Corvette...s/Springs.html
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I'm taking care of my procrastination issues, just you wait and see.
Old 02-21-2013, 01:29 PM   #3
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Originally Posted by blckslvr79 View Post
Looks like it broke. Time for new ones.

Nice thing is front coils can be bought new very inexpensively.
On sale right now.

http://www.vbandp.com/C2-C3-Corvette...s/Springs.html
Yep. It has been broken since I bought the car in 1985. Didn't handle all that bad though. Maybe I can break the other one so the ride height is the same on both sides.
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Old 02-21-2013, 01:36 PM   #4
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Originally Posted by Mattydale View Post
Yep. It has been broken since I bought the car in 1985. Didn't handle all that bad though. Maybe I can break the other one so the ride height is the same on both sides.

With that many coils gone, you'd be low ridin'. I'm betting you'll notice a big improvement in handling now.
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Old 02-21-2013, 02:55 PM   #5
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Hi Tom
I thought you are supposed to start by removing one coil at a time to get the low rider look!
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Old 02-21-2013, 05:27 PM   #6
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Hi Tom
I thought you are supposed to start by removing one coil at a time to get the low rider look!
Gary- I figured if 1 is good, 4 is better.

All my friends know the low rider
The low rider is a little higher
Low rider drives a little slower
Low rider is a real goer...

You do such good work on the Diffs & Steering Boxes I figure I'll send you the spring and you can fix it for me.

No worries. I know you got my back.
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Old 02-23-2013, 04:53 AM   #7
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When you buy the replacement springs don't freak out , they will be shorter , and the difference will make you wonder if the car will sit a lot lower . It wont
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Old 02-23-2013, 06:01 PM   #8
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When you buy the replacement springs don't freak out , they will be shorter , and the difference will make you wonder if the car will sit a lot lower . It wont
There is no correct direct replacement for the OEM #3931826 spring at this time. The Moog (AMG5762) Rate 474 Ht 13.13 same as 331318 is for a non-AC car. The LS5 454 and AC options resulted in GM producing the 3931826 specifically for those options. I don't want a stiff ride even if the ride height is correct. The F41/550 is too stiff. I'm in contact with a few coil spring manufacturers and they claim to be able to reproduce the 3931826 correctly for me... at a price. We'll see.
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Old 02-23-2013, 06:17 PM   #9
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Quote:
Originally Posted by Mattydale View Post
There is no correct direct replacement for the OEM #3931826 spring at this time. The Moog (AMG5762) Rate 474 Ht 13.13 same as 331318 is for a non-AC car. The LS5 454 and AC options resulted in GM producing the 3931826 specifically for those options. I don't want a stiff ride even if the ride height is correct. The F41/550 is too stiff. I'm in contact with a few coil spring manufacturers and they claim to be able to reproduce the 3931826 correctly for me... at a price. We'll see.
Volunteer Corvette has a spring with the same rate as the Moog you discuss above. Are you saying that would be too soft? We're getting ready to completely rebuild the front end as well, so what you are finding will be helpful.
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Old 02-23-2013, 08:46 PM   #10
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When I replaced my springs they were correct for a L46 small block convertible with out air and they were shorter. The ride height seems to be close,perhaps a tad high,but I have found that they are a bit stiff for my liking. I don't know what they are rated at. I wish,at times,I would have reused the old springs that had a smaller dia. coil.
If you know of a softer replacement I would be interested in the supplier.
Thanks.
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Old 02-25-2013, 08:13 AM   #11
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Quote:
Originally Posted by XQIZT View Post
Volunteer Corvette has a spring with the same rate as the Moog you discuss above. Are you saying that would be too soft? We're getting ready to completely rebuild the front end as well, so what you are finding will be helpful.
If you are referring to the SU12H, that is listed for a NON AC BB. The picture shows 10 coils but there is no guarantee that the pic is actually of the spring in question.

The SU12H specifies "BB 4-SPD ALL; BB AUTO W/O AIR" and a 475 rate. This raises a red flag to me because GM did not have a "BB 4-SPD ALL" spring. The tags on mine are clearly 3931826, not 331318. This needs some clarification. Their SU12F looks like the Moog spring.

I am finding:
1) Many vendors are just reboxing the Moog spring and doubling or tripling the price. Fool me once, shame on you. Fool me twice, shame on me.
2) Many people are installing the Moog spring and say that the ride height is not affected even though the free length is several inches less. I believe this, but I don't believe the ride is the same as the OEM spring as this is a subjective matter.
3) GM created the 331318 specifically for NON AC BB cars. This apparently matches the Moog spring at some level. They developed the 3931826 spring for AC BB cars. They wouldn't have gone through that whole costly design and production process unless they had a reason.

Even though people attest that the Moog spring works fine, I am skeptical. I don't want to be the guinea pig here. I only want to do this once. I'm willing to pay a little more to get the right spring.

To complicate mattters, I am media blasting and painting all of the front end parts and the spring install tends to chew everything up requiring massive painstaking touch-ups. I also don't want to do that twice.

Several people have quoted a "325" number for the 3931826 but I don't know where that number comes from or what it means. The GM Parts catalog (group 7, p.7-1 C) has a build chart for 1972 19437 (coupe) which puts the spring at base 677.5lbs +A31/power windows 2.5lbs +C60/A/C 39lbs + J50/Power Brakes 4lbs +LS5/454 99.5lbs +N37/Tilt Wheel 1lb +N40/Power Steering 13lbs + U69/AM-FM Radio 3lbs + U79/Stereo Radio Amp 1lb for a total sprung weight (in my case) of 840.5 lbs. Don't know how this relates to the scheme of things but thought I should include it here.

It would seem likely that the 3931826 is somewhere between the Moog spring 474/ the 331318/475, and, the F41 550 spring.

FYI- The unbroken 3931826 spring on my 70 has exactly 10 coils and a free length of 15 inches at 95,000 miles.

I have a few more routes to try before I join the masses and use the Moog springs for $50. I can't justify paying the extra bucks for the incorrect repro 331318 when the rate is nearly equivalent to the Moog. Waiting for responses to my inquiries.

Hope this helps rather than adds to the confusion.
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Old 02-25-2013, 08:31 AM   #12
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Matty...you've clearly done extensive research on this issue! And I certainly appreciate the concept of "only doing this once." ABSOLUTELY!

I was thinking about going with the Volunteer SU12F, since it is listed for SB W/ AIR.

In your case, maybe get a hold of someone who does NCRS type restorations and see where they source their parts from. I am sure that they are aware of this issue and can point you in the right direction.

Let us know what you come up with!
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