CadVetteStang

If you were going to build an autocross car, and could have any C4 year model to start out with, what year would you get and why? (Engine considerations do not count in this discussion because it will have an engine swap before it races – this is just about suspensions) The car will also be a daily driver.

ekess744

FOR a solid "A stock" car
89 z51 manual zf6

a couple good reasons come to mind

good axel ratio (3.54 or something near that)
stiff springs
can bolt on upgrades more easily than the 84 (miniram, c5 brakes, c5z06 wheels etc)

USAsOnlyWay

The 89 was shown to be a very capable car, also I believe the 86 Z51 was also a good one (ABS but still fairly stiff.)

However you said you were going to swap the motor and things change A LOT when you change classes. For instance, if you are going into SSM then you'd probably want an 88+ car so you can mount coilovers more easily. Also, since you are going coilovers the Z51 package won't matter as much.

What are your motor plans/what class?

ekess744

[QUOTE=USAsOnlyWay;1571471883]The 89 was shown to be a very capable car, also I believe the 86 Z51 was also a good one (ABS but still fairly stiff.)

However you said you were going to swap the motor and things change A LOT when you change classes. For instance, if you are going into SSM then you'd probably want an 88+ car so you can mount coilovers more easily. Also, since you are going coilovers the Z51 package won't matter as much.

What are your motor plans/what class?[/QUOT

knowing what class you want to race in will dictate the choice of car IMO. I stand by what I said about the 89z51 for "a stock" though

If you want to get crazy about the mods, look into vert as it has a stiffer chassis stock. However, I believe you can add the same bracing to a coupe with a kit.

1991Z07

'91 Z07

Quick ratio steering box (only offered on the Z07)
Power steering cooler (only offered on the Z07)
Heavy-duty springs (only offered on the Z07)
Heavy-duty roll bars (only offered on the Z07)
High durometer LCA bushings (only offered on the Z07)
J55 13" front Brakes
Oil cooler
Same size tires/rims on all 4 corners (stock 275/40-17...only on the Z07)
ZF6 MN6 (Black tag)
FX3 suspension (I know I'll get knocked on this one...but I've owned mine since new and have had the shocks rebuilt once, and it has nearly 70k miles on it now. Have had to replace 1 shock actuator as well).

When I was Autocrossing regularly, I was spanking highly modified C4 cars (engine-wise) when all I had was a pure stock drivetrain and got bumped a class for exhaust system changes. The suspension was the reason. Once I changed out the bushings to urethane, it was a real route...I had to do that because the high durometer rubber bushings were not available from GM, and they had no LCA assemblies in stock anymore.

Once I went with rebuilt shocks, I had them done to Rippie specs (with a new controller and chip) and the car handled like it was on rails.

The other choice is a pre-change (suspension) car. I forget what year they changed the rear geometry, but the offset was different on the early C4's and you can fit 315's on ZR1 rims on the rear (and fit them INSIDE the rear fenders). Gives you more bite for the motor mods...

c4cruiser

An '89 won A Stock in this year's SCCA Nationals. When they came out, that year was pretty much unbeatable.

Once you start doing mods to the suspension or engine, then it will probably be the car that works with the mods you do.

mnstrlt1

i agree with the comments here, seems as though the 89 or the z07 car's are the best platform. The later cars will be a royal pain in the a$$ to get the chassis computer, engine computer, etc worked out with your swap.

BADDUCK

Also quick steering, oil cooler, dual fans, HD radiator, J55 brakes, 17" wheels, better seats and suspension than later years or Z07..
Ask me how I know

Race Prepared

Speaking from experience - 1989 6 speed, an excellent base setup to build on!

ekess744

I knew I was forgetting a few

Mojave

For A Stock, proved again this year by another win (most of any year), the 89 6 spd Z51 is the best car.

Other solid choices: early LT1 Z07's (like 92-93?), 86 or 87 Z51, or 96 LT4 Grand Sport (mostly clones, heavy and soft, but 315's on the rear and more power than the rest).

corvette95

84 has the most agressive suspension of the C4 line.

BADDUCK

Yep, it's an *** beater alright.

mr.beachcomber

According to Corvette Quarterly (Fall 1990, p. 19), The 1991 ZR-1, Z07, and Base FE1 suspensions all used the standard 15.7:1 steering ratio.

I'm pretty sure that the quick steering option was dropped after the 1989 model year. (Can't find any reference for that other than hearsay, Internet babble though.)

There is a big difference between the two steering ratios. When my local Corvette club acquired a permanent auto-x site, I used to let the newbies auto-x my '89 auto because it was a safe car to overdrive as it wouldn't bite the driver or damage the car (as long as you didn't stay in the throttle until you hit something or someone).

I didn't let anyone drive my '89 Z51 6-spd car until a couple of years ago at a banked 1/4 mile NASCAR track, and then it was only for their parade lap around the auto-x course. The feedback that I got from experienced drivers was that the steering was "scary fast" even at low speeds.

batchman

The 88 Z51 is credible too. Only real difference from 89 is the 4+3, which if it's in one piece, isn't a problem.

I'm building a 91 ZR-1 for BSP, the quick rack is one of the first things we did. I don't believe it was available after 89.

Later,
- Jeff

scorp508

87-89 Z51 are all very similar to each other. There's also the Z52 if you want just a slightly less *** beating.

ekess744

Based on what? Spring rate? they are all very different In suspension geometry. Read up

And z52 was just a fancy way of saying base model. Even though there was a true base model for 88, the numbers were pretty small

jhammons01

Only took 12 post to get there.........

1991Z07

Well, according to MY build sheet, I have the B1X Optional steering ratio installed on the car.

The car came with:

AC1 - Power passenger sport seat
AC3 - Power driver sport seat
AQ9 - Sport leather seats
B1X - Optional Steering ratio
C2L - Dual Roof Panels
FE7 - Performance Suspension
FX3 - Selective Ride
J55 - High performance brake package
KC4 - Engine Oil Cooler
GM3 - Rear axle 3.45 ratio
G87 - Ring gear 8.50 inch
L98 - Tuned port injection 5.7 L engine
ML9 - Manual 6-speed, ZF-transmission
MN6 - 6-speed manual transmission
QA1 - Styled aluminum wheels, 17 x 9.5"
U1F - Delco Bose stereo system with CD and cassette
UX0 - Delco Bose six speaker system
U52 - Electronic instrument cluster
XAU - Front tire P275/40 ZR17
YAU - Rear tire P275/40 ZR17
Z07 - Adjustable Performance Handling Package
10U - White Exterior
24S - Blue Roof Panel

It (B1X) does NOT show up on the console door codes, but it is on the build sheet (which I have the original from the frame rail as well as the reprinted and laminated copy from the museum).

I ordered the car...did a lot of soul searching before I finalized it. Somewhere in a file I have the original order sheet along with all the included options with the Z07. It came as the baddest combination of everything they learned from the Corvette Challenge series and had every performance bell and whistle they had...

There are a BUNCH of other codes on the build sheet that don't show up on anyone's lists...I think I'd need to take it into a dealership parts department to decode it all. I know one of them is for the "special" lower control arms...I'm sure others are for the interior color, etc...

It was also the last year for the L98...

Rumor and hearsay dispelled...

1991Z07

But aggressive does not equate to best...

If you are racing on a pool-table smooth track, it is a GREAT suspension. But it is SO stiff that any ripples in the pavement make it bounce like mad. Stiff is not always the best.

Also, the engines (and the 4+3 transmissions) sucked in the '84's (IMO).