minitech

Maybe I'm getting too old for this or getting more sensible about these these things. I used to think like most as far as I can see that if it is better for racing or performance it is just better...

I would first think about what the car is used for. Not "Hope to bring it to a real track one day (And 99% NEVER DO), I go to a 1/4 mile once per year and hope other people will see me go real fast, etc..."

If you trailer the car to the track as a dedicated track car that is one thing. And you likely are working with a much more sophistocated setup then just changing shocks.

For me I drive the car on nice days and hope to have a smooth stock like ride. I took off the Bilsteins it had because it bounced too much for regular road drivimg and replaced with modern stock like shocks. It is great now and it has parts for whet I use it for most of the time.

I can always bring it to the track each year if I want with the stock like ride but MOST OF THE TIME I just drive it.

Build your car for what you do with it. Don't put one part of a performance car, suffering the side effects and never use it for that.

So my vote is to ask what the performance specs of the stock shocks were. Ask for a modern shock with similar specs.

aaroncorvette

I wanted a vette that would handle as well as it can within a reasonable budget.
So i looked at the suspension and decided what works and what needs to be changed. The c3 has a high ride height in stock form and in stock form the car doesn't appeal to that much, it just looks like an old car, the lines are there, and it's beautiful, but it looks dated, just my opinion.

So, bigger wheels were the start, to fit 285/40/17's required a shorter spring (1"), E bracket moving and the sway bar removing.
Then I lowered the rear with longer bolts, this put the half shafts higher at the wheels than the diff. I looked around at ways to raise the diff and thought modding the crossmember was the most logical.
3/4" is the most you can do without cutting the floor of the car, the diff is tight up against the floor at the moment, not touching but tight.
if I did it again i'd mod the floor and put the diff up higher.
The welder cut a 13" section from the crossmember and welded it 3/4 lower, with reinforcing inside.
I didn't change the pinion angle as it's a minor diff move, a spacer put in/removed would work, best to get the car up in the air and check the prop angle first before you do the mod (I didn't so I have no reference).
Smart strut is stock and in it's lowest eccentric setting is fine, just try to get the rod and halfshafts parallel as much as poss and be done with it.

Oh I also removed the shocks, spring and bump stops and manually pushed the wheel as far up in the arch til it hit something, then allowed 1/2" (I think from memory), then cut the bump stops down, this gave an extra 3/4" travel (again from memory), this is vital on a lowered car, any travel you can find the better. (same with the front)



Ideally a lowered car should have shorter shocks but mine work fine at stock length.

Have a look through this lot - http://s877.photobucket.com/user/aar...?sort=3&page=1

Crossmember - http://s877.photobucket.com/user/aar...ml?sort=3&o=29

I've just applied common sense to get the geometry right at approx 3" lower ride height.

Front - offset top arms, borgeson steering conversion, mono spring, cut down stops, bump steer kit

Solid LT1

Is that a real Lola T70 your crossmember is perched on? Hope the owner of that ride never checks your posts or Internet photos, you would have some serious explaining to do around shops I frequent treating a ride as a prop for a frame member photo.

v2racing

No kidding! With some of the guys I know you'd be wearing that crossmember on your head!

v2racing

Here's what I think about adjustable shocks. I think the majority of people wouldn't know how to really use them to better the handling of their car. Even George (gkull), a guy who works with race cars and has a lot of track time, alludes to that in this thread from a couple years ago. I'm not saying that no one here can handle dialing in their car, but I'm sure more would have trouble with it than those who could really benefit from the adjustability.

My 80 with the F41 suspension had new NAPA (Monroe) shocks on it when I got it. It rode very nicely for a C3, but it would dive into corners, the front end would dive under hard braking, and under acceleration with my 406 in it, it would feel like it was doing wheelies. I put a set of Bilstein Sports on it and it was a completely different car. Cured all of those issues. It rode a little stiff, but not bad.

My 75 came with 550 springs front and a 360 glass spring on the rear. It had Bilstein HD's on it. The front was fine, but the rear bounced a lot. Enough it would make you queasy after a while. I'm completely redoing the suspension and steering on the 75 and it is getting Bilstein Sports for now just for simplicity and cost. Down the road I may upgrade to QA1's.

Kinda on the same subject. I followed a C3 down the road for about 5 miles the other day. I could see it had a glass spring on it. It was bouncing like a carnival ride. I don't know how anyone could stand to drive it like that. Way worse than what I described in my 75 with the HD's, and I couldn't stand that.

aaroncorvette

I 100% agree that adjustability sounds great but can get you in a mess real quick.

The Lola is the welders car, not mine, awesome bit of kit. I needs a crap load of work and the crossmember on his roof is the least of his worries. He took the pics.

jb78L-82

I completely agree as well

My 78 L-82 4 speed originally equipped with the F-41/Gymkhana stock suspension road very hard, bouncing over big bumps like a truck, especially in the rear. After 30 years of tinkering with the suspension, I came to the conclusion that there are 2 inherent problems with the the C3 suspension, too much frame flex and too much suspension movement, in general.

The front suspension is generally not bad BUT the frame flex must be addressed and I did with one of the best investments one can make in the front suspension, a spreader bar-mine is a Speedirect one ($100) designed to be used with the stock mechanical fan. Many folks don't like poly upper and lower control arm bushings but I use them as well to eliminate unwanted control arm movement and found that they made the front feel really planted AND did NOT make the ride harsh. I use 550 springs 1 inch shorter than stock currently and have used Delcos, KYB's, Koni oils, not gas shocks, and currently Bilstein HD's with the 550 springs. The current setup is so much better than the stock front F-41 step up and is stiff but not harsh.

In the rear, the same deal-too much suspension movement with my 360 mono spring installed in 1986. A few years ago, I swapped out the Bilstein HD's for the sports-in the rear only with the HD's up front. Transformed the ride and handling. The other big change was the addition of competition adjustable struts with Heim joints-no bushings too deflect. Solved the bouncy ride issue and the car is really planted with a firm,NOT harsh ride.

After all the suspension tweaking over 30 years, I finally concluded that I had to go to 17/18 inch rims to get rid of the crap 15 inch tires available for these cars-This is a MUST for a good ride. The 15 inch tires make the car bounce all over the road on their own-the sidewalls are too big and too soft. Currently run 255/45/17 ZR ultra high performance summer only tires-transformed the ride, steering, and handling of the car alone!

I wish many of you could actually experience how my 78 rides today with all the modifications to the suspension and steering (GTR1999 custom blueprinted/ rebuilt OEM steering box). It would be very enlightening!

Hope that helps!

aaroncorvette

Oh yeah I forgot about the frame flex, it's terrible.
If someone had told me this before I started modding the car i'd have put a roll cage in first.
I can feel the jolts transferred through the car.
It's a tad difficult putting a cage in a 'vert but it will happen eventually.
It's not like there's loads of room as it is....

v2racing

Yes, the frame flex. I have that problem stuck in my head and I'm not sure what to do about it. This is mostly a street toy, but I will do an autocross now and then. I would like to have at least a loop or dual loops for some safety in a roll over, but a full cage just is a little much for a street car.

I have a spreader bar for it and solid motor mounts. That will help the front a lot. I am going to take the rubber cushions out of the differential and raise it 3/4" by the weld in disk method and a solid front mount. That stiffens the rear up a lot, but there is a lot of flexy frame in between the front and the rear. I keep thinking what can a guy do besides a full cage to tie the front and rear together. Haven't come up with anything yet, but the gears are turning and the smoke is coming out of my ears!

donyue

I have the Koni adjustables for the front with 550lbs springs and Bilstein sports for the back with the VBP dual mount spring (came with the rear kit from VBP).

I haven't installed the new suspension yet, I will be working on that upgrade this coming spring.

I am not expecting that this setup will give me the best suspension available for a C3, however I do expect it will be an noticeable upgrade from the stock 36 year old systems. I will also be installing a Borgeson steering kit with the new suspension.

These upgrades should make the car more responsive for steering and suspension capabilities.

I had a look at the QA1 and the coil over systems originally, but the cost was too much for me and I was only looking to upgrade for spirited street driving and some possible autocross use.

The car is not going to be raced on a track but it is not a daily driver either. It will just be a fun and safe car to drive fast.

7t2vette

The reason I even started this thread was because I was trying to get rid of some bad wheel hop issues. When my car had a TH400 auto trans in it, I could do John Force style burnouts all day long with no wheel hop at all; then I switched to a TKO-600 5spd and then had the wheel hop issues. This was with no other changes to the driveline.

I thought maybe I needed better shocks to dampen the rear suspension better to control the hop. I removed the 8yr old 3 way adjustable Carrera shocks and found that they were worn out. I replaced them with the single adjustable QA1's, and after I had them adjusted to my liking and driving style, I found they did improve the wheel hop issues a lot, but not completely. So I am now on a mission to get rid of the hop completely.

When I did the body-off resto to my car, I prepped the frame by fully welding all the seams and adding all the recommended gussets.

Front suspension consists of:
-VBP tubular upper control arms with offset cross shafts
-VBP front composite spring conversion with tubular control arms
-VBP spreader bar
-QA1 single adjustable shocks
-all poly bushings

Rear suspension consists of:
-Van Steel c-channel trailing arms
-VBP 360lb composite spring
-VBP adjustable struts
-VBP diff crossmember locating discs
-QA1 single adjustable shocks
-all poly bushings

Now I am considering either mounting the diff solidly to the frame or going to a stiffer rear spring, perhaps even a dual-mount. Maybe even both.

I am thinking that the hop came from 2 reasons:

1) the torque convertor in the previous auto trans acted as a fluid dampener of sorts while the manual trans allows the drivetrain to be hit harder by the engine

2) the engine is putting more hp to the wheels because the manual trans has less losses

Any insight to wheel hop issues? I am also considering the VBP traction bar, but I think I would rather just solidly mount the diff to the frame.

gve

If you turn the QA-1s all the way in does the wheel hop go away?
The fact that it improved with better shocks means its still to bouncy in the rear, you may have to go to the 420# spring.

DJmaya

I switched from Bilstein sports to QA1 single adjustable. I could not believe the difference. QA1 all the way! And if i want it stiffer I just turn the ****, it takes 1 minute.

Richard Daugird

I'm glad this old thread came up, lots of good info. How many of you guys with lowered cars and stock length shocks still up and running? I will definitely be lowering mine.

rogernison

I have wondered about a 3/4" spacer between the differential & strut rod bracket with grade 8 bolts. Seems like in would accomplish the same thing without altering the u-joint angles. Don't know of the downside or any negative effect on handling.

revitup

Bilstein HDs with new 550# coils and 330# 7-leal steel rear. Firm but not bone jarring. I'd do it again.