My brother has a C6 Grand Sport. My daily driver is a 1989 Z51 6-spd. I drove his car a bit recently and told him that driving my car afterwards felt like driving a chuckwagon. It's pretty astounding how improved the C6 feels. Frankly, it was hard to concentrate on driving his car with the oppressive lack of squeaks and rattles it involves. I could barely focus in that maddening silence.

I was left wondering how close to that feeling of rigidity and responsiveness a C4 could be modifed to reach. My car is pretty much bone stock and I have no firsthand experience at making these kinds of improvements--just ideas. Who here is familiar with both generations and has some experience improving the C4?

I would speculate that the two main areas that would make the most difference would be front suspension geometry and chassis stiffness. For the former, I'm anxiously waiting to hear results from the forum member who's mixing pre and post '88 IFS parts.

For chassis stiffness, I'm aware of the common things. Targa brace, framerail tension bars, convertible cross brace. None of those are really on my list, though. I'm thinking it would take a full on cage of some sort to approach the stiffness of the C6 chassis but I'd like to hear what others think. My own blue sky idea is to rip out the fiberglass front half of the floor/firewall and rebuild it in steel while incorporating a plate bolted to the bottom of the tunnel to fully enclose it and finally tying that whole thing into the frame rails at front and rear like they did on the C5. That's well beyond current practicality, though.

Someone is going to come along and say that a C4 will never feel like a C6 and just buy a C6. I know this. I'm just curious how close it can get. Like maybe percentage-wise.

 

I own both, a 2012 Centennial GS (4LT, Coupe, MN6... yeah it's sick and my unicorn spec) and a 92 C4 with some stiffness mods.

If I was gonna put a number to how close you can get I'd say it's like... 30% stock, 40% if you throw the best of everything at it. The chassis stiffness of the C6 is unreal, and then if you get the stiffer GS suspension, and/or the magnetic ride dampers... It's an absolute monster of a chassis. Almost boring in fact, because you really can't get near its limits without significant training. You may think you are near the limits, but you're not. At most you're just out speeding your skill.

The other big difference that you simply can't change between the two is the space inside. The C6 is significantly more spacious, with more passenger space and more storage space. That's just something you can't change in the C4.

You can add the brakes, the engine, and you can approximate the weight balance too. A C4 can still really handle quite well, and if you go through and add anti vibration material to the panels you can quiet them up some. Put a nice Ridetech setup under the C4 and it's gonna drive real nice. But you're never going to get that same chassis stiffness, even if you like seam welded the chassis and did a full cage. It's simply just made with far better materials and with far more engineering and purpose to it.

I drive my C4 more than my C6 because it's more fun. The extra chassis stiffness is nice for a cruiser and performance limits, but the limits on the car are so high it's honestly kind of a snooze besides just stomping on it for 4-5 seconds before you're in felony level speeding.

 

Cut out the rest, because I don't know, hah... but on the squeaks and rattles, most of that is because of the age of the car. I've completely restored three cars in my lifetime, a Porsche 944, a Pontiac Fiero, and a VW Bus. The closest to the 84 Corvette would have to be the Fiero (since they are basically built almost identically, SMC, space frame, etc.). What you'll want to remember is that the body did not squeak like that when it was new. You may have had a little flex (being that it's a targa), but these cars didn't squeak like this when new.

I've had at least a dozen Fieros, and also this Corvette. I bought one Fiero back in 1996 with only 52k miles on it, and it didn't squeak at all. My daughter recently restored a 1985 Fiero 2m4 SE... body off space frame, the works. It has zero squeaks. It doesn't matter how insane you toss it into the turns and how crazy you drive it. The cabin is dead silent other than the engine and a little bit of road noise. What happens typically are the seals between the SMC and the frame will rot out and deteriorate, leaving the body panels to effectively rub in certain places where they previously would not have. It's easy to see these under the hood, those strips that go around the sides of the cowl where the hood latches. There's also things like door pins and such, where the bushings start to wear just enough that the door is now wearing away at the striker and now squeaking against the rubber bump-stops. If you were to totally restore the Corvette... as in, take the body off, re-do all the felt and foam inserts (all of which is available in higher quality than stock from Amazon), you'd have a squeak-free C4.

Can't say anything about the handling though, as I've never owned a C6. We are effectively planning on doing this to this 1984, despite any logic or financial common sense. We spent almost 25 thousand dollars restoring a 4-cyl 5-Speed Fiero that only cost $4k, so don't look to me for common sense! Haha... but my daughter did all the work so I kind of viewed it as a life building / learning experience for her... almost like an early college education. And, I've got to spend the money on something...

But just like that Fiero, we bought the least-desirable, biggest rat of an 84 Corvette that was barely running, and will probably do the exact same thing against all common sense and logic. It'll probably be worth $8k when I'm done, and we'll likely have spent about $15 on top of the $4,000 we spent buying it. Haha...