Hi guys.Allow me step up to the Forum help desk.Time to replace the rear spring in my 1978.I count seven leaves and 2 1/4" width in my car now.A local guy said he would sell me a 9 leaf and said mine is heavy duty and the 9 is standard.WTH, isn't a 9 leaf more heavy duty than 7,logically????Anyway I'm not buying used as I don't need 2 bad ones.Wilcox ,you out there?Thank you.

 

It sounds to me like you have a FE7 Gymkhana optioned car, This came with the 7 leaf spring which was indeed a much heavier spring.

Willcox

 

Really ,Wouldn't my car have a rear sway bar?It doesnt now.I will never race this car, so wouldn't the nine leaf ride better? Thank you.

 

Offered from 1974-1982, the Gymkhana FE7 cars had different front springs, shocks, 1 3/32 front sway bar, a rear sway bar I think it was 7-16" and the 7 leaf HD. spring.

The 7 leaf spring is a harder riding spring than the standard spring. Would the 9 leaf be a good replacement, yes. It is a smoother spring ride wise.

Willcox

 

Hum. . . Any chance there are two holes one on each side of there rear spring bolt (one in front and one toward the rear) in the trailing arm? This would indicate a bar was present at one time or another.

Willcox

 

Not sure.It's here now ,but I can Check tomorrow.I will probably order the nine leaf.Will it affect ride height? Car sits too low in rear compared to the front.

 

If the spring is a factory arch, it should raise it a little.

Willcox

 

I've found the 9 leaf (new) to be a bit too soft and wallowy, at 196lb/in, bad highway manners. The 7 leaf (new) is a better feeling spring, at 315-330lb/in, though you do feel the rear bumps. I found the 9 leaf (new) to be way too soft. and that's on a '73. The 'Vette had pick up some additional weight by 78 fyi. C.

 

I believe that the base suspension spring for a 78 vette is 300 lbs/in versus 360 lbs/in for the F-41 sport suspension vettes. Begining in 1980, GM concentrated more on luxury than handling and the spring rate differential grew more between the base and sport suspension vettes with I know the 82 vette with the base suspension having the 200 lb/in spring rate. I do not believe that a 1978 vette or earlier vettes having a 200 lb/in spring. I have had a composite spring in my 78 since 1986/87 and have a 360 lb/in spring for my F-41 suspension. I would definitely NOT buy another steel spring if you are looking for the best of all worlds:

composite springs offer:

1. A much better ride than a steel spring, ie, a 300 lb composite will ride MUCH better than a steel spring of comparable rating. In fact, I would rather have a 300lb/in composite spring than a 200 lb/in steel spring

2. A composite spring is much liighter than a steel spring, 8 lbs versus 50 lbs.

3. A composite is MUCH quieter than a steel spring.

4. A composite spring will not sag over time, they do not wear out.

Someone may have replaced your 9 leaf rear spring with a 7 leaf, F-41 spring. If you do not have a rear sway bar on your 78, you do not have the sport suspension. F-41/gymkhana suspended 78 vettes have a 1 1/8 in front bar-check that out.

If you want a very good ride in the rear, you may want to go for a 300/315 composite rear spring. My 360 composite with Bilstein HD shocks rides real nice and handles great.

 

I agree with everything jb78l says regarding the composite spring but beware you might have a problem getting the ride height where you want it with a composite. I had to swap out 3 different springs before I got the ride height to an acceptable level and even still I ended up having to use 10 inch bolts. The longer bolts are a definite worry because if you have a tire blow out the bolt will hit the ground before the rim does. I can only imagine what that will do to my rear suspension.

 

You are incorrect. There are 2 9 leafs, an early-68- *early*78 196lb/in and a late *late*78 through 81? the late '78-on 9 leaf was 260lb/in and is 2.5" wide vs 2.25" on the early springs. The 7 leaf can vary by manufacturer, but is nominaly rated at 330lb/in. If you have a '78, measure your rear spring width, as they came with both, that year, the wider spring later in the year. I agree that a composite is the way to go, if you don't have a problem with the extra cost.

 

I wasn't sure about the base spring rate and stand corrected! Sorry about that mistake which is why I said "I do not believe". I was basing that remark on vendor recommendations more than technical fact since for example, Mid America states their standard composite spring is 315, performance is 340, and heavy duty is 355. I guess, I am curious as to why the vendors would recommend a 315 lb spring for base suspension vettes when the OEM steel spring is 196 lb which seems to be a big difference? I see you corrected your original post at the same time I wrote mine that their are 2 different 9 leaf springs. Thanx.

Also, I used a VBP 360 in place of my 7 leaf steel spring, non tapered, and had zero issues with ride height. It seems that certain tapered springs like the TRW ones, create ride height issues. Just an observation but again, not fact.

 

See my revisions, as i did a bit of research on that point myself. Early springs were 196lb/in though, there a wallowy spring, a 7 leaf 330 is a much better fit for the cars purpose, and is just adequate imo, from having recently used both springs, both new. a '78 put on a couple of hundred pounds over my '73 too, so maybe a 360 composite would be a good fit for the original asker. that's about where i think i would go in. C.

 

Again, I agree with you that a 200lb rear spring is way too soft for our types of cars, maybe that is why vendors offer springs from 300-420lb in the composite spring. I think most vendors recommend a 300 lb spring for base suspension vettes and about 360lb springs for F-41/gymkhana vettes. In my opinion, the 360 is just adequate for my F-41 78 and in fact, I switched recently from Bilstein HD's in the rear to Bilstein sports in the rear only since they are 30% stiffer than the HD's. When my spring needs to be replaced (doesn't appear anytime soon, though), I may look into a 400-420 rear spring coupled with Bilstein HD's in the back. Where did you get the rear spring rates since I would like to have that info too? Thanx.

 

The spring I ended up with was the same spring you used (VBP 360). I still had ride height issues though it was better then the TRW springs. I still had to use the 10 inch bolts. Maybe it's because I have a BB convertible or maybe it's because these old vettes were all a little bit different when manufactured.

 

Check front sway bar- 1 1/8" is the Gymkhana which has the 7 leaf rear. The Gymkhana front springs are 550.

I replaced the FE-7/Gymkhana 7 leaf rear w/ VB&P composite.

 

Hi, did some checking.Rear of trailing arms only have one large hole for spring bolt.I don't see two holes in frame that would line up sway bar brackets. Front sway bar is 7/8"(I only see 1" as smallest replacement bar listed).The spring pad bolts look like they have been changed.BTW,car is an L-48.As much as I would like the composite,pay cut dictates steel spring.I'm thinking another 7 leaf at this point.Thanks for the input all good stuff.

 

All the C3's have the two holes for a rear sway bar on top of the trailing arm on each side, whether the car had a stock sway bar or not-it's cast into the trailing arm. The only way to see these holes is to take the wheel off and look down at the top of the trailing arm. You probably cannot see it from crawling under the car but you could feel it with your hand from underneath. I would replace the front 7/8in sway bar with an aftermarket 1 inch or 1 1/8th inch arm and mount the bar with poly bushings to the frame and use poly end link bushings. In the rear mount a 7/16th rear OEM sway bar with the OEM/Stock end links and see how you like that first before deciding if you want a larger rear bar, 5/8 inch or 3/4 inch bar with the OEM type end links-I would stay away from the aftermarket rear sway bars of 3/4 inch or definitely 7/8 inch diameter with a non stock end links, IMHO.

 

It's best to have a balanced setup so you need the 9 leaf which came on it w/o other changes like stiffer front springs.

 

Again, good advice! Since the car did not have the sport suspension, I would either stick with the base spring (9 leaf) in the rear without a rear bar OR you need to change the follwing components to make it a F-41/gymkhana suspended car:

Front:

1. 550 lb front springs

2. 1-1 1/8th inch front sway bar

Rear:

1. At least a 330lb spring or possibly 360 lb spring-Steel or composite with the latter preferred IMHO.

2. 7/16th rear OEM/stock sway bar

255/60/15 tires.

Presto-Gymkhana/F-41 car!