Another coil spring question...

[Mike R.]

I have a 65 L84 car. The rear spring does not appear to be original (no curl on the leaf ends) and the front springs have .685 wire. I don't know the free length since I have not yet removed it. My question is whether the F40 front springs are the progressively wound design or not? Also I would like to find a correct looking F40 rear spring that yields correct ride height with the stock hardware (bolts/cushions). Does anybody have experience with the springs from Duntov Motors or America's Finest Corvettes? Thanks

Mike

[Joe L.]

Re: Another coil spring question...

I have a 65 L84 car. The rear spring does not appear to be original (no curl on the leaf ends) and the front springs have .685 wire. I don't know the free length since I have not yet removed it. My question is whether the F40 front springs are the progressively wound design or not? Also I would like to find a correct looking F40 rear spring that yields correct ride height with the stock hardware (bolts/cushions). Does anybody have experience with the springs from Duntov Motors or America's Finest Corvettes? Thanks


Mike

Mike------


The F-40 front springs were not of the progressive type. These springs had a free length of 12", 7 coils, and wire diameter of 11/16". I believe the GM "official" free length of the springs was 10.84". However, by my measurement of NOS springs, I get 12". Take your pick, though. In any event, they're shorter than any of the other springs used from 1963-73.

By the way, the same front springs were used for all F-40/F-41 applications from 1963 to 1973.

[Mike R.]

Re: Another coil spring question...

Thanks, this helps a lot!

Mike

[Ronald L.]

Re: Another coil spring question...

Joe,
Revisiting this, the 66 AIM calls for this:
F40 EA 3832518
L36 L72 EB 3888250

What is the difference in these two springs?

[Joe L.]

Re: Another coil spring question...

Joe,
Revisiting this, the 66 AIM calls for this:
F40 EA 3832518
L36 L72 EB 3888250

What is the difference in these two springs?

Ronald------


Well, the 3888250 is the standard spring for big block applications and the 3832518 is the spring for F-40/F-41 HD suspension. In general configuration the 3888250 is longer with smaller wire diameter than the 3832518. The 3888250 is rated at 2250 lbs and the 3832518 is rated at 2344 lbs.

[Ronald L.]

Re: Another coil spring question...

Joe,


So with out a doubt the 3888250 was the spring for the base L36 - - -
That is non F41, no AC, etc.???

Somewhere not many months ago I seem to recall someone saying that all big blocks got the F40 - but I think that can't be from trying to count coils on a fully assembled car.

[Bill M.]

Re: Another coil spring question...

Ronald------


Well, the 3888250 is the standard spring for big block applications and the 3832518 is the spring for F-40/F-41 HD suspension. In general configuration the 3888250 is longer with smaller wire diameter than the 3832518. The 3888250 is rated at 2250 lbs and the 3832518 is rated at 2344 lbs.

And the 3888250 is a variable rate (some closely wound coils). It looks like the 327 standard spring, but is just a little longer. The wire diameter on the 3888250 is 0.600.

[Wayne M.]

Re: Another coil spring question...

.... The F-40 front springs were not of the progressive type. These springs had a free length of 12", 7 coils, and wire diameter of 11/16". I believe the GM "official" free length of the springs was 10.84". However, by my measurement of NOS springs, I get 12". Take your pick, though. In any event, they're shorter than any of the other springs used from 1963-73.....

Here's a pic of NOS F40/41's.

[Bill M.]

Re: Another coil spring question...

Here's a pic of NOS F40/41's.

May as well post these too!

Here are the 3888250 (top; 427 w/o A/C
and the 3888251 (bottom; 427 w. A/C)

[Ronald L.]

Re: Another coil spring question...

Joe & Wayne - thanks a picture is worth 1000 words. I have both a NOS F40 set matching Wayne's picture with tag, etc. I can recall in the 70's buying a F41 set from GM with green paint and a green tag, but that was a long time ago.

And most important, the originals in the car are as Bill shows for the larger diameter 427 version.

So much for those F40's they don't work on this car. Thanks again!

[Joe L.]

Re: Another coil spring question...

Joe & Wayne - thanks a picture is worth 1000 words. I have both a NOS F40 set matching Wayne's picture with tag, etc. I can recall in the 70's buying a F41 set from GM with green paint and a green tag, but that was a long time ago.

And most important, the originals in the car are as Bill shows for the larger diameter 427 version.

So much for those F40's they don't work on this car. Thanks again!

Ronald------


I have several NOS sets of the F-40/F-41 springs [none for sale] but you'd NEVER catch me using them on ANY street Corvette. Never. Ever.

[Ronald L.]

Re: Another coil spring question...

Joe,

I agree with you there, I'll trade my F40's for the x250 springs. That is original and the ride is just fine now I took off the gold lines and put on a set of 215/70 Indy 500 Firestones.