65 progressive springs

[Bill M.]

Re: 65 progressive springs

Bill-------

There were actually quite a few Corvette springs that used this same wire diameter. However, I really believe that Daniel has the correct springs. The 3851100 was, by far, the most common C2 small block spring.

I agree, Joe. He got 3851100s off a '66 327.

The 3888250 spring was also 0.600 wire diameter and the same number of coils, just wound a little longer. It was used on the C2 big blocks without A/C. You can only tell them apart based on free length. (Now if he had 3888250s, he could use 3851100s to drop it....)

[Daniel D.]

Re: 65 progressive springs

Thanks Bill. Joe has provided all the dimensions for 3851100 including overall length of 15-7/16". Do you know the overall length of 3888250? Or are the various specs published together somewhere? I'm now thinking about removing the springs to get to the bottom of this since I've been hung up on it for a few years now. From the various posts, it seems likely that I have the correct 3851100, but from the pictures I posted earlier, it can't be determined for sure since other springs would appear to be visably similar. I purchased these springs from a Craigslist add in 2011 ... I saw the car that they came out of. I'm pretty sure it was a small block coupe, but don't know whether it had AC, etc. One more thing, the Z measurement of 2.45 +/- .25 inches in the AIM is the correct number that I should shoot for, right? Thanks.

[Duke W.]

Re: 65 progressive springs

Spring specs are in the AMA specs that are part of the "vehicle information packages" that you can download, free, from the GM Heritage Web site.

Duke

[Bill M.]

Re: 65 progressive springs

Thanks Bill. Joe has provided all the dimensions for 3851100 including overall length of 15-7/16". Do you know the overall length of 3888250? Or are the various specs published together somewhere? I'm now thinking about removing the springs to get to the bottom of this since I've been hung up on it for a few years now. From the various posts, it seems likely that I have the correct 3851100, but from the pictures I posted earlier, it can't be determined for sure since other springs would appear to be visably similar. I purchased these springs from a Craigslist add in 2011 ... I saw the car that they came out of. I'm pretty sure it was a small block coupe, but don't know whether it had AC, etc. One more thing, the Z measurement of 2.45 +/- .25 inches in the AIM is the correct number that I should shoot for, right? Thanks.

The free length Joe has provided for 3851100 is wrong. I assume he got them from the AMA specs, but my numbers are straight off the CE print, which is the ultimate authority. No offense intended to Joe or Duke, they are "the man" for most of this stuff. I have NOS 3888250s and they are the same length as the CE print spec.

3851100 free length is 16.88; print says for 327

3888250 free length is 17.35; print says for 427 (mine measure 17.25 inches)

The 385110 was used on all 327s; with or without A/C

Yes, the ride height you have is "right". I had the same issue with my '65 as you; too high. I went to F40 springs, but if I were in your spot, I would just cut the springs you have. I haven't done that myself, so maybe someone who has cut springs can help how much to lop off....

My hot rod with F40 springs:

[Timothy B.]

Re: 65 progressive springs

Thanks Bill. Joe has provided all the dimensions for 3851100 including overall length of 15-7/16". Do you know the overall length of 3888250? Or are the various specs published together somewhere? I'm now thinking about removing the springs to get to the bottom of this since I've been hung up on it for a few years now. From the various posts, it seems likely that I have the correct 3851100, but from the pictures I posted earlier, it can't be determined for sure since other springs would appear to be visably similar. I purchased these springs from a Craigslist add in 2011 ... I saw the car that they came out of. I'm pretty sure it was a small block coupe, but don't know whether it had AC, etc. One more thing, the Z measurement of 2.45 +/- .25 inches in the AIM is the correct number that I should shoot for, right? Thanks.

Daniel,

Lets see what others say about that Z dimension, I think the AIM dimension and the service manual spec say different things. On 63, the service manual says 3 1/2" I think.

[Stewart L.]

Re: 65 progressive springs

The free length Joe has provided for 3851100 is wrong. I assume he got them from the AMA specs, but my numbers are straight off the CE print, which is the ultimate authority. No offense intended to Joe or Duke, they are "the man" for most of this stuff. I have NOS 3888250s and they are the same length as the CE print spec.

3851100 free length is 16.88; print says for 327

3888250 free length is 17.35; print says for 427 (mine measure 17.25 inches)

The 385110 was used on all 327s; with or without A/C

Yes, the ride height you have is "right". I had the same issue with my '65 as you; too high. I went to F40 springs, but if I were in your spot, I would just cut the springs you have. I haven't done that myself, so maybe someone who has cut springs can help how much to lop off....

My hot rod with F40 springs:

Back in the 70's and 80's I was into the race car look, I would cut a half coil off each end. That will drop it down a couple of inches.
I remember the first 66 I bought in 1973 sat high like Daniels. I don't think it had ever been altered before I got it. From what I remember I dropped it down with a set of F40 springs front and rear.
So if you don't want to purchase more springs, cutting a half a coil off each end would drop it down. Maybe one of our engineers can speak up if that adversely affects the spring rate but from what I recall, thats what they used to do on the SCCA race Corvettes I crewed on.
Stewart

[Joe L.]

Re: 65 progressive springs

The free length Joe has provided for 3851100 is wrong. I assume he got them from the AMA specs, but my numbers are straight off the CE print, which is the ultimate authority. No offense intended to Joe or Duke, they are "the man" for most of this stuff. I have NOS 3888250s and they are the same length as the CE print spec.

3851100 free length is 16.88; print says for 327

3888250 free length is 17.35; print says for 427 (mine measure 17.25 inches)

The 385110 was used on all 327s; with or without A/C

Yes, the ride height you have is "right". I had the same issue with my '65 as you; too high. I went to F40 springs, but if I were in your spot, I would just cut the springs you have. I haven't done that myself, so maybe someone who has cut springs can help how much to lop off....

My hot rod with F40 springs:

Bill------


I got the spring free length from a quick search in Noland Adams' book. However, as I look again, I find that he shows the 1964-66 springs at 15.40" and the 1967 springs at 16.82". The problem with that is that most all L1964-67 Corvettes used the same GM #3851100 spring and I really don't think the specifications for that spring changed between 1966 and 1967. His 1967 dimension is probably the correct one for the 3851100 spring.

I've got quite a few NOS examples of this spring [none for sale]. I'll try to dig one out and measure it.

[Daniel D.]

Re: 65 progressive springs

Bill, that's a good looking car. And I like the ride height.

[Daniel D.]

Re: 65 progressive springs

Thanks to all who have replied. I really appreciate this. Yes Timothy, I did notice that the Z dimension is significantly different in the 63 service manual (3 5/8") than in the 65 AIM (2.45"). I know that 63s are different in a lot of ways, but I wouldn't think the height would be much different.

Dan

[Bill M.]

Re: 65 progressive springs

Bill, that's a good looking car. And I like the ride height.

Thanks, Daniel. Good luck with your project. Let us know what you wind up doing.

[Daniel D.]

Re: 65 progressive springs

Thanks Duke. I just spent some time reading through info on GM Heritage site. There is some interesting stuff in there. I think the consensus is that the free length of the springs might be a typo, but nevertheless, there is a lot of good information there.

Dan

[Daniel D.]

Re: 65 progressive springs

It was suggested that I try to locate a pair of NOS 3851100 springs. If anyone has a pair they would be willing to sell, please contact me by email. Thanks.

Dan

[Daniel D.]

[Bill M.]

Re: 65 progressive springs

The 3888251 drawing has wire diameter of 0.573 and free length of 17.15 and constant rate of 220 lb/in (not progressively wound).
Mine measure 0.57, 17.13 and 16.75, 9 turns.
Looks like you have 3888251 springs.

[Daniel D.]

Re: 65 progressive springs

Thanks Bill.

Dan