yesterdayscorvettes

I want to put C4 front suspension on my '66, but I'm not sure what year C4 suspension to use. I'm being told that '84-'87 wheel base is close to that of the '66, so the rack n pinion would bolt up and it wouldn't mess up the steering geometry. '88-'96 have a wider wheel base. I'm looking to keep the same wheel base as the original '66. Others have told me that there is no difference in front wheel base 84 -96, the only difference is a bigger rotor in 89-96. I have a 15 inch rim I want to use on the front of the car, so I have to make sure it fits. I want to use all the part of the C4 front, a-arms, steering knuckle, calipers, rotors, rack. This way everthing in the front is Corvette. I'm not looking to change the whole frame to make this work, I just want to eliminate the coil spring tower and convert to coil overs and have my frame man weld C4 brackets to the C2 frame and bolt the control arms to the frame (I hope it's as easy as it sounds). I might have to have more mods done to the frame to make the C4 work than just welding bracket to it. If anyone can give me some direction, I would appreciate it. Thanks!!!!!!

jim lockwood

What you are wanting to do is a big job. Period.

The track ( wheel base is the distance between front and rear wheel centerlines) of the C4 suspension is measurably wider than that of the C2 suspension. To make the end result look "right", you'll be wanting to narrow the mount points for the upper and lower control arms. Once you do that, you can no longer use the stock C4 rack and end up with correct geometry.

However, if you go through with your project here is some data:

'84 - '87 (early) front suspension is slightly more narrow than '88 - '96 (late).

To run 15" wheels, you'd have an easier time using the early suspension because the rotors have a smaller diameter (~11.5") which locates the caliper more favorably.

The early C4 brakes are significantly less capable than the brakes currently on your '66. You'll be giving up a lot if you use them.

Late suspension can be used with some 15" wheels, but only if you use the 12" rotors and matching calipers. Even with this combination you might have to shave some material off the calipers to gain clearance. Like the early brakes, these are not as capable as the brakes now on your '66.

Overall, this is a big job with, in my opinion, marginal payback. I wouldn't do it.

Jim

cbernhardt

A friend of mine in Australia wanted to put C4 suspension on his car and the regulations over there forbid cutting or altering the original frame. His car was a '62 but the picture below will give you some idea what you are up against. I have a lot more closeup pictures of the front suspension if you are interested.
Charles

yesterdayscorvettes

Hey Jim,
Do you know how much longer the a-arms are on a C4 vs C2. If I move the mounting point in on the frame I have to worry about interfering with the engine or headers. I'm just trying to get a mental picture of how much I have to move the mounts in. I want to get all the info I can before I do this. Thanks for you info, I appreciate it.
Dan

jim lockwood

Not off the top of my head. I'll measure a late C4 lower control arm later today when I go to my shop and get back to you. The upper control arm will be approximately the same length as the one on a C2.




I think you'd find the engine and the upper control arm mount clear each other nicely..... the engine sits somewhat rearward. As for headers, you'd want to hook up the steering first and then build headers that clear.

However, the real issue, the biggie, the matter that would make me think long and hard about doing this conversion myself (or doing it at all) is preserving correct steering geometry. Choose the wrong length for your new steering rack, or locate the rack improperly either in elevation or fore/aft position and you'll risk having truly unpleasant and potentially dangerous steering properties.

Do you have access to a bump steer gauge?

Jim

jim lockwood

Late C4 lower control arms are about 15-1/4" from centerline of ball joint to centerline of pickup points. Early C4 lower control arms are about 13-1/4".

Jim