Ron78Z&66Vette

I should have my frame powdercoated in a couple of weeks and am getting ready to order all the stuff I'll need for the re-assembly.

I'm looking at Zip's suspension rebuild kit that comes with the front & rear springs. http://www.zip-products.com/Zip/prod...5A3D48A55A1E24

Only thing I'm wondering is if the springs might be too harsh. The rear composite spring is 355/360 lbs and the front coils are only described as being "similar to F-41" specs (I'm assuming that they are rated @ 550lbs).

I plan on using poly bushings, 2XX/7X/15 radials (not sure exact size yet) on stock wheels, 1" front & 3/4" rear sway bars, and KYB shocks. Not sure if it matters, but the engine is a 327 with A/C and I will probably be running aluminum heads.

The car will be close to a daily driver with no track use other than an occasional pass down the 1/4 mile.

I'm not against a "stiff" ride as I previously owned an '85 Corvette (non Z51) which my wife thought rode "rough", but I thought it was just fine. I know what I'm asking is VERY subjective, but if any of you have any first hand experience with this heavily rated of a spring set-up I'd like to hear your opinions.

macdarren

That is pretty much what I run....different shock, but mine is a small block with AL heads and AC. I think you will find it pretty firm but nice up front but the rear might be a bit harsh especially with that heavy a rear bar. I ended up removing the bar all together (mine didn't have one from the factory and considering it has been slightly lightened and has a stiffer spring setup I found the rear bar just made that bump in the road that only hit one wheel just a little too jarring....keeping the tank full helped a little as did a passenger. I think you would be ok if you like it firm and you can always unhook one side of the the bar if you want to try it that way just for comparison. I suspect I didn't have enough shock so that might have been why I found it harsh.


Just for comparison my daily driver is a very stiff sprung solid bearing solo car, and I like that ride just fine 3 hours a day, but in the 65 that 360 and heavy bar felt wrong in the rear. I am going to try it again with a different shock and still no bar as soon as I get her back together.

63 340HP

When considering the 66's ride quality, the 85's low profile tires and the old school 70-series rubber are light-years apart. The tall sidewall flex and the resulting pneumatic spring effect in the 70-series rubber provide a tunable spring rate in the tire: more pressure = higher tire sidewall spring rate = harder ride. The high frequency jolts and road imperfections that tickle & jar your backside in the 85' (or with the F41 spring package) can be soaked up and dampened by the tall tire sidewall simply by lowering the pressure. The tall tire sidewall dampens the road imperfections before the springs and shocks can be forced to work, resulting in a smoother ride.

What tire pressure adjustments cannot tune out of the suspension is the low velocity cross-coupling effect of the swaybars. A load on one side of the vehicle (crossing a rut or speedbump at an angle) will demand shock and spring travel, and the suspension travel is limited by the combined corner spring and swaybar spring rate. This is why macdarren mentions the rear swaybar can make the ride seem harsh, because you lose some of the low velocity independent suspension benefits with the bar installed. This may be one reason GM did not install a rear swaybar on small block corvettes until well into the 1970's (after the enthusiast driving public became more used to stiff cross-coupled suspensions).

Most street drivers with tall sidewall tires do not notice the F41 suspension's higher corner spring rates unless they pump the tires up for competition fun (and eliminate the "spring" in the tire sidewall). Running the 24-28 psi factory tire pressure recommendation in a modern 70-series radial will net a fairly compliant ride (compared to modern ride expectations). Pumping these radials up to 35 psi will net traction far superior to any of the stock bias ply tires of the 60's (the popular P4000's performance probably exceed the lateral traction provided by similar width 60's era GY Blue Streak rain tires).

I do not know what the motion ratio of the C2/C3 suspension is by design (anyone?), but I expect the factory spring rate to place the effective wheel frequency to be well below 1.3Hz.

One caution I have is the KYB shock performance. KYB's Engineers tended to overdampen the shocks for a competition-oriented ride (and I do not know if they have made recent changes in their product). Their valving philosophy tended to make the shocks stiff on small bumps (road ripples and uneven expansion strips). The unique valving of Edelbrocks and the digressive dampening options the different Bilsteen shock offerings provide (or the adjustable QA1's) will probably net you a more compliant low-speed street ride without sacrificing the high-speed performance potential of a modern 70's-series radial.

I run a high-pressure Monroe built shock tuned to after-market tuner specs (Guildstrand/Rancho) but would upgrade to modern Edelbrocks if I were buying shocks today.

66427-450

I've owned both std, and F-41 (current 66 BB has F-41 springs/bars, with Bilstein Sport shocks).

based on what you describe, i think you'd be much happier with 460 coils and a 330 composite spring. i personally don't care for a composite spring on a Midyear, it came with a leaf, that's what belongs there :-)

seriously I'd give VBP a call 800 237 9991, or go to VBandP.com The most important thing is to get a balanced "system"

Sky65

I had VBP 460 front springs and 330# rear composite spring. I cut the fronts springs approx 3/4 coil to lower the front. The rear spring was too stiff so I replaced it with a 300#, actual rating 285#. Still too harsh. Replaced the BS with Koni adjustables. Much better. SB manual trans driver.

jobber26

The only difference in your plans and my finished set-up is I cut 2 coils off the 550# coil springs and installed Bilstein gas sport shocks and a 7-leaf Duntov spring (330#) and 2" offset trailing arms and 8" spring bolts to lower the car 2" all way around... it handles like a dream! People say those C3s don't handle and then I take them 60mph on a 25mph rated off ramp just to get a look at their faces!!! I tell them, the C3s needed a little help in the suspension dept!

old68

is that a 7 leaf spring? I have f41, and the front is fine, the rear was chattering all over the place , just shaking the car apart, I ended up using the longer bolts and raising the car up and it smoothed out, hopefully whatever spring you use will set a proper ride height and not too high,

jobber26

Yes, it is a 7-leaf spring from Duntov.com and it mimics the F41 part. I also moved down to a 5/8" rear sway bar to try and avoid an over aggressive rear end... I was going to go to 3/4" and my mechanic said not to go with a thicker rear sway bar because of problems binding the independent trailing arms... I also have the adjustable rear strut rods that my alignment guy used to spread the tires just a frog hair for cornering... I did go aggressive on the front with a 1-1/4" sway bar and the 550# springs (2 coils chopped). I wish you didn't have to raise your car back up to avoid the chatter; it's such a fluid feel when it's right down on the tire tops!

TJefferson2020

I run that set up in my 64 with Koni Classic adjustable shocks. 1.25" anti sway up front and .75" on the rear. Poly bushings.

Car is on rails. Only issue is that there is zero warning when you lose adhesion. No squeal, no cowl shake - nothing.

Some might describe the ride as "harsh" - I like it. I feel super secure and connected to the car and road. Off ramps at 85 mph are no problem.

Rear rides a bit high for my tastes with composite spring (bolts are as long as they can be) but I like the feel of the composite over the steel spring. It is certainly lighter.

larrywalk

I am running 460 lb/in front springs with 330 lb/in fiberglass rear spring. I have a 1" front sway bar and had tried using a 3/4" rear sway bar, but I discovered that the car was divergent and would lose grip suddenly - not something you want to have happen on a curvy off ramp. Further, the car was slower on the autocross with the rear bar than with it disconnected. I finally removed the rear bar altogether for better handling and quicker times.

FWIW, the 330 rear FG spring was less harsh than the 7-leaf steel F41 spring.

63 340HP

Holy dusty archive Batman, this thread started in 2006 😏

Move along, nothing new here, just good stuff.

jobber26

85MPH Off Ramps is KICK ***!!!!!!!! I get squeamish at 60!!!! I'd have to take a shot of whiskey to try that one... you got nerves of steel my man!!! Hey, another dude on the forum says that the 1984-86 9" spring bolts will fit the C2s and C3s rear spring and let you come down another inch or so, if you don't like the ride height... not sure how this will effect your handling... also, have you had any problems with your mono-spring delaminating? I hear they are possibly vulnerable to this from rock blows.