I have a line on a used fiberglass spring. It came off of an 80. The owner of it thinks it is aftermarket. I was wondering if it would fit on my 78? I can say it is the type that the outer ends are wider than the middle. I can't see any type of name on it anywhere, although there is a sticker with a part number and serial number. anyone have any ideas?

 

What you described sounds like the spring sold by Muskegon Brake. They list (link below) composite springs for 1963-77, 1978-79, and 1980-82.

Presume you are wanting to use the spring on your 1978. The fact that it came off an 1980 (aftermarket - no OEM composite springs in 1980) would indicate it would not work on your 1978. A call to Muskegon might be useful.



http://www.muskegonbrake.com/v4/go.g...&listTemplate=

 

To say the least, IMO, being a happy customer for some16+ years now, VBP and Bilstein shocks are the way to go....my plastic spring is 360 lbs then suffering with the KYB shock for years, upon advice from here I went Bilstein...SO much better on my ***....

CASE CLOSED.....

 

Sounds like You have a TRW style spring wich is what came on a 81-82 Vette and were also sold on the Aftermarket. It should fit You 78 just fine however the Mounting Brakets may be a bit diffrent. If so You may be able to buy them with out the spring. I have little or no doubt somebody has done this before on this sight. You might try the Search above.

 

So what are the numbers?
does it have something like 602-??? for a part number? The TRW style had three boxes for the last three digits and one would have a hole punched in it to mark what the rate was
Mooser

 

I had KYB shocks with a 360 lb VBP for years also and replaced the KYB shocks with Bilstein Sports. HUGE improvement.

 

Thanks for the info guys! Moosie, the part number does start with 602, it is as follows but the third set of numbers is unreadable. 602-101-xx3-105

any opinions on the TRW spring, and installing it on a 78? I am looking for improved ride, handling is not my main concern.

Thanks!

Edit: I am looking at a picture of this spring and got thinking..the reason one of the sets of numbers is unreadable is because it looks like there was a hole punched. I see TRW listed 3 springs. a 315, 340, 355 pound. Maybe because the second box is punched, it is a 340 pound? Any idea how this compares to stock?

 

Yes that should be a 340lb spring.
Compared to stock? I think the stock 78 was around 260 or something. Problem is you can't really compare the steel to glass very well, seems like I see a lot of guys running the 315 on small blocks. I have a 355 on my BB.
The strange thing is that number seems to match the 68-77 springs, they list a different number for 78-79
Best to make sure it's the right one for the 78
Mooser

 

If you want a nicer ride, look at the Hyperco EZ ride composite spring. The rate is about 200 lbs. Eckler's and Van Steel both sell them. I put one in this autumn and I can't believe how well it rides. You will need a good pair of shocks. The Bilstein Sports are well recommended, but I am using Delcos, and, so far so good. The only issue is that the spring is the 2 1/2" wide pattern, requiring smaller bolts to fit the diff housing on the earlier cars..

 

My 78 L-82 4 speed with the gymkhana suspension was completely stock when I bought the car in 1983 with 25,000 miles on it-7 leaf steel rear spring with the OEM AC delco shocks. The car rode like a truck not just stiff but very harsh.

As noted above, switching from a steel spring to a fiberglass composite is not an apples to apples swap since the composite spring has much different rebound/compression characteristics compared to a steel spring. One of the advantages of using a composite spring (and there are many and the reason GM stopped using steel in 1982 completely) is that you can go MUCH higher on the spring rate with composite with a MUCH BETTER ride quality and handling characteristics versus steel.

In 1986, I purchased a VBP 360 spring (which I still have in the car) to replace the 260 # steel gymkhana spring and was shocked at the superior ride and handling characteristics of the 360 composite spring! In general, C3's IMO are sprung way too soft in the rear from the factory (probably due to the ride characteristics of the steel spring) and have way too much flex in the front and rear suspensions with the rubber bushings. The 360 spring with the appropriate shocks (I use Bilstein Sports in the rear only, HD's in the front with the 550 springs) rides much better than the steel 260 spring and has much better reaction time compared to the steel one. When and if I need to replace the 360 composite in the future, I will probably go with a 420 rear spring. Keep in mind that my current setup in the rear:

360 Monospring with poly cushings
Bilstein Sports
Competition adjustable strut rods with Heim joint ends (no bushings)
3/4 inch OEM type rear sway bar with poly mounting bushings
255/45/17 ZR Ultra high performance summer only tires

is superior in ride and handling characteristics to the OEM setup of:

7 leaf 260 steel spring
AC delco shocks
OEM strut rods with rubber bushings
7/16 inch rear sway bar.
255/60/15 S/T rated tires

Hope that helps!

 

Thanks for the help guys

 

 

Just a couple more questions please...
I saw a post I can't find again about which composite spring brand to use and what not to use. I remember there was a brand not to use.
Will the pounds change the ride height in the rear?
(I'm switching out my old 7 leaf in my BB 69)