Early C4 Verus Late C4 Handling

[93Rubie]

I was wondering what would (stock) handle better. A early C4 84-87 with the Z51 package or a later C4 (88-96) with the base suspension. I would assume that a later Z51 or Z07 car would handle better than an early Z51 because they totally changed the suspension setup for 88 to a zero or negative scrub radius? I cannot remember which.

So early Z51 or later base?

 

[Hib Halverson]

If we are talking about pure, at limit handling, the best cars were the 85-87 Z51s.

 

[93Rubie]

So if I was going to buy a C4 for track use a 85-87 Z51 might be the best option from a handling perspective?

I would think a 89 or later Z51 or Z07 with a ZF 6 speed might be the better more rounded choice.

Hmm...

 

[JohnGrawcock]

The early C4's were much more aggressive. Customer complaints about the harsh ride resulted in a much more street friendly setup on the later cars. I've got an 84 with standard suspension and a 96 Z51. The 84 I'd put on the track as is. On the 96 Z51 I'd want stiffer springs.

 

[vetteoz]

The early C4's were much more aggressive.

If you reference Hib's suspension chart you can see how much softer the later cars were

http://www.idavette.net/hib/c4/sustunch.pdf

 

[Hib Halverson]

So if I was going to buy a C4 for track use a 85-87 Z51 might be the best option from a handling perspective?

I would think a 89 or later Z51 or Z07 with a ZF 6 speed might be the better more rounded choice.

Hmm...

Your question confuses the issue.

Do you want a C4 for track use and focused on at-limit handling or do you want a C4 which is a "more rounded choice.?"

Also, if the goal is just track use, I wouldn't use a C4 at all. I'd find a used 02-04 C5 Z06, reset the alignment, put on some sticky tires and go have fun. Unless the C4 is highly modified and on race tires, the C5 Z will run rings around it.

Now if the goal is to have a track day C4, then the early chassis is better for handing so, the obvious solution is to swap in an LT4/ZF 6-sp powertrain.

 

[93Rubie]

Hib, I was think about this last night and came to the same conclusion. A C5 Z06 would be the ideal track car,they where designed for it. Problem is they are still 20K+.

So why did they change the suspension geometry in 88, if the earlier setup yielded better performance?

What I ment Hib, by "more rounded choice", is that the SBC and the 4+3 are not exactly track friendly compared to the LT/ZF6, but as you suggested a swap would fix that.
A LT1 or LT4/ZF6 swap should be a straight forward swap, I would think.

A earlier C4 would obviously benefit from the later wheels as you can get performance rubber for them, easier. That and fit bigger brakes. Oh, crap the gears in my brain are turning again.

Could with aftermarket suspension components a later C4 be brought UP to earlier C4 specs.?

When I get to looking into something I want to know everything, just the way I am. Heck, I read Dave McCellans book Corvette From the Inside. While being a good book and I learned a lot it left me with even more questions. He should have provided more technical details than he did. Stupid Lloyd Reuss and his darn targa top. Dave had a drawing of his proposed C4 structure in the book, and it looked in many ways not unlike the C5 minus the T roof of course. Could have had a stiffer car but no we had to change things and then not have enough time to make changes to compensate. Management still STINKS.

Nice to know that when my top is out the structure is so weak the first frequency is below wheel hop and only marginally above it with roof on. Amazing the C4 is as good as it is.

 

[Hib Halverson]

(snip)
So why did they change the suspension geometry in 88, if the earlier setup yielded better performance?

The change in the front was mainly to optimize handling and braking performace during ABS braking on split-mu surfaces.

What I ment Hib, by "more rounded choice", is that the SBC and the 4+3 are not exactly track friendly compared to the LT/ZF6, but as you suggested a swap would fix that.

??I would not characterize the small block-Chevy as "not track friendly". Also, The "LT" IS a small-block Chevy. I agree that the Doug Nash is a POS transmission for track use.

A LT1 or LT4/ZF6 swap should be a straight forward swap, I would think.

Well....it depends on your definition of "straight forward".

A earlier C4 would obviously benefit from the later wheels as you can get performance rubber for them, easier. That and fit bigger brakes. Oh, crap the gears in my brain are turning again.

The brake issue is significant.

Could with aftermarket suspension components a later C4 be brought UP to earlier C4 specs.?

I don't understand the question...are you asking if a late C4 can be backdated or retrofitted with the early parts or are you asking of a late C4 can be modified such that it's handing performance mimics that of an 84-87?

When I get to looking into something I want to know everything, just the way I am. Heck, I read Dave McCellans book Corvette From the Inside. While being a good book and I learned a lot it left me with even more questions. He should have provided more technical details than he did. Stupid Lloyd Reuss and his darn targa top. Dave had a drawing of his proposed C4 structure in the book, and it looked in many ways not unlike the C5 minus the T roof of course. Could have had a stiffer car but no we had to change things and then not have enough time to make changes to compensate. Management still STINKS.

The C4 structure is terrible. This is why, back in the C4 era, "harness bars" were such a useful mod to a C4. Even with shitloads of aftermarket parts, unless you put a roll cage in the car, a C4 will never have the handling at the limit like a C5.
The folks don't understand that when you have a stock C4 structure and you increase the cars roll stiffness and lateral grip beyond that of OE Z51 levels, you begin to bend the structure with cornering loads. Once you do that, at the limit, the car gets less predictable on the track. The C4 coupe structure was a leading edge design for the late 70s but Ruess wanting that targa bodystyle was a major FUBAR. I know the retired-GM guy who was first to cut the T-bar out of one of the early C4 protos. I also know the retired-GM guy who did most of the test driving back then. He told me when they began to test that car, it's handling was quite a bit worse than that of the existing C3. It wasn't until they added those big side rails to the car's frame and bolted the roof in place that the handing got better than C3.

Lastly, this discussion is not to say you can't use a C4 for track day event, but it is to say that if you really want to go fast on a road course and you're skills are such that you really drive the car to it's limits, a C5 is far better choice.

 

[93Rubie]

Ok, sorry for any confusion or being a PITA.

The L98 does not strike me as being well setup for track use. Lack of HIGH RPM power is my main point. LT1 has much broader torque curve and high RPM power, which at least to me would be at least more fun on a road course.

Again sorry for the confusion...I meant can a later C4 fitted with aftermarket springs, shocks, etc...be made to handle similar to the earlier Z51 cars?

Mainly I want another C4 because they are cheaper, than a C5. Also, they are what I am most familiar with. Lastly, I am new to auto cross and road course action so a cheaper car and slower is a good way to get my feet wet. So to speak. Then in the future when C5 Z06's are cheaper buy one of those and go really nuts.

Thanks, all for being informative.

 

[John Robinson]

I think the real question is not if a C4 can be made to handle for auto crossing. The real question is until the driving skills have superseded the cars ability then any C4 will give the driver a thrill if they can push it to the limits. The next question seems to me to be that modifying a C4 to handle like a C and claiming it is to keep the cost down because the C4 is cheaper is false economy. By the time you buy a decent C4 and make the modifications you are talking about to make it as good as a stock C5 Z06 you will have more then the cost of a decent C5 Z06 in the C4. I say this because the other day I had a 30 something fellow in a 370Z try to out run me on a twisting road from a stop light down to a 70 MPH right hand corner. I am not so vain as to think that my 17 year old car can out perform the handling of a 370Z but when we got to the right hand corner I had to back off so he could drop into the corner up to that point I was flat out driving him on the curves leading up to this tight right hand corner as well as out accelerating him. As a 70 year old guy with handicap plates in a 17 year old car I should not have been able to out run this fellow but he lacked the ability to get the performance out of his car. I hope that instead of going off somewhere and spending a ton of money to make his car faster he instead goes to a good driving school and learns how to reach the limits of the car he has.

 

[Hib Halverson]

(snip)
I hope that instead of going off somewhere and spending a ton of money to make his car faster he instead goes to a good driving school and learns how to reach the limits of the car he has.

John Robinson gets the Monday morning Beacon of Reality Award.

 

[93Rubie]

I totally agree with you John, but please reread my posts. I NEVER said I wanted to make any C4 handle like a Z06. You really could not even if you tried. I am in search of the best C4 for track use and clearly the earlier 84-87 cars suspension is superior. I would argue the later cars drive train is better than the earlier cars, anything with a ZF6.

I would like to get into the sport so a cheaper but capable C4 is what I am after. I was merely trying to figure out which C4 to get. If a earlier car is better than there is no need to find a later C4. Spending 20K on something I am new too is dumb, so 5K or so is more like it.

I asked if a later C4 could be modified to handle like a earlier C4 because I prefer the ZF6 to the 4+3.
As Hib noted the 4+3 is garbage for track use.

I am not going to use the Ruby for auto-x or road course use. Its purpose will be built around a Street/Strip combo. Otherwords I am planning on leaving the suspension/brakes mostly stock, but optimized for my purposes of spirited street driving with occasional 1/4mile passes.

 

[John Robinson]

Grounds

I totally agree with you John, but please reread my posts. I NEVER said I wanted to make any C4 handle like a Z. You really could not even if you tried. I am in search of the best C4 for track use and clearly the earlier 84-87 cars suspension is superior. I would argue the later cars drive train is better than the earlier cars, anything with a ZF6.

I would like to get into the sport so a cheaper but capable C4 is what I am after. I was merely trying to figure out which C4 to get. If a earlier car is better than there is no need to find a later C4. Spending 20K on something I am new too is dumb, so 5K or so is more like it.

I asked if a later C4 could be modified to handle like a earlier C4 because I prefer the ZF6 to the 4+3.
As Hib noted the 4+3 is garbage for track use.

I am not going to use the Ruby for auto-x or road course use. Its purpose will be built around a Street/Strip combo. Otherwords I am planning on leaving the suspension/brakes mostly stock, but optimized for my purposes of spirited street driving with occasional 1/4mile passes.

OK I understand your rational about which model would handle the best and needing to keep the cost down is a good goal as well. Just be aware that the older the C4 the greater the chance you will have to replace all the bushings, shocks and various other suspension parts to get the suspension back to the condition to be run hard. I would way the advantages of a later model C4 that might not need to have much done to make it ready for your baptism into auto crossing. My understanding is that the L98 is a torquer and the LT1 (my experience) is the torque comes on higher up the RPM range. I would opt for the lower torque because most auto crossing is not high speed. However if you are talking about track days then depending on the track the Lt1 may be better suited for the longer straights and higher speed corners. But most importantly go and have fun and don't forget to drive your car and not get caught up in the heat of trying to beat someone else. That's the fastest way I know of to find your self in over your head.

 

[93Rubie]

OK I understand your rational about which model would handle the best and needing to keep the cost down is a good goal as well. Just be aware that the older the C4 the greater the chance you will have to replace all the bushings, shocks and various other suspension parts to get the suspension back to the condition to be run hard. I would way the advantages of a later model C4 that might not need to have much done to make it ready for your baptism into auto crossing. My understanding is that the L98 is a torquer and the LT1 (my experience) is the torque comes on higher up the RPM range. I would opt for the lower torque because most auto crossing is not high speed. However if you are talking about track days then depending on the track the Lt1 may be better suited for the longer straights and higher speed corners. But most importantly go and have fun and don't forget to drive your car and not get caught up in the heat of trying to beat someone else. That's the fastest way I know of to find your self in over your head.

That is a good point and one I did not think of. Then again it would all depend upon the kind of shape its in. I could always with a later C4 upgrade with aftermarket suspension. I'll have to see. I'll have to weigh the L98 versus LT1. Decision-Decisions...

I know when I took the 93 to the drag strip I made up my mind I was there to race myself, and only me. I have since always went with that mind set. My first run ever was a 13.88 best now is 13.52. I know for a fact the car is faster, I have never had a totally clean run, my goal is to get 13.4. I know the car will and I can if I try hard enough. Then I'll want a 13.3, but that might be pushing it without starting to think about modifying the car more.

 

[Rogue]

Why not just spend $2k-$3.5k to put a higher performance suspension system and braking system on your C4 and then take it to the track? Must you have a track car in addition to your current C4? If you just want to have fun there, you don't need to beat the crap out of it, just drive it to YOUR limits and then go from there. You said so yourself, you are just racing against yourself, which is really saying, your doing it for fun and not be completely competitve against others. Having seen what other people take to the track, you are already ahead in many ways with your C4 because even though its inherent structre is inferior to a C5, it is superior to cars like Mustangs, Camaros, etc. and even 1990's vintage 911's. If you feel you must improve the structure, put a camber brace and cross bar in it to reinforce the structure and go have fun.

 

[Rogue]

I'll have to see. I'll have to weigh the L98 versus LT1. Decision-Decisions...

For the track, the important thing is that manual transmission. The Automatic with its limited shifter control just won't cut it. The 6-speed would be ideal.

You can easily mod the L98 to put out respectable power up to its redline. You won't gain any RPM's but with a freer flowing intake, Cat back exhaust, custom chip to take advantage, your car will suddenly run stronger than you imagined to redline. The L98 won't be gasping for power up there. Unless you're trying to beat C5's, the TPI L98 is good enough motivation on the C4. For fun running it's more than enough. I've seen guys with Miata's running less than 150 bhp and they're still having a ton of fun. They learn how to maintain their forward momentum, not bleed off energy as much in the corners, use the corners to catapult themselves to the next straightaway to maximize what little power they got. Fun stuff.