rachels

I HAVE AN 87 C4 THAT IM GETTING READY TO HPEFULLY BE COMPEDITIVE WITH MY DAD WHICH WAS 5TH IN THE NATION TWO YEARS AGO. HE IS ALSO BUILDING A C4 RIGHT NOW AND A LOT OF TRASH IS BEING TALKED. SO FAR I HAVE 315'S ALL THE WAY AROUND ON ZR1'S. I BOUGHT THE AUTOCROSS BILSTIEN SHOCKS, ZZ9 CAM FROM TPIS, CHIP, 1.6s, PORTED AND POLISHED HEADS, UNDER DRIVE PULLYS. DYNOMAX WELDS, GUTTED CAT/RESINATORS, AND I RECENTLY WELDED MY ROLL CAGE IN. WHAT I NEED IS CAMBER SPECS THAT ARE GOING TO WORK THE BEST WITH MY SETUP. IT IS A Z52 CAR.

PLEASE EXPERIENCED ADVICE ONLY

THANKS

bogus

there is a section dedicated to autocross and road racing. From the top menu bar, Forums ==> General Corvette ==> Autocrossing & Road Racing.

Check it out. I am SURE that good specs are there.

Also, seek out forum member BrianCunningham. He has gotten the C4 to handle very well.

Is your car an automatic or manual? Either way, I would convert it to a 5spd TKO from Keisler. It's a pricy upgrade, but the A4 will kill you from power loss and poor gear selection, and the 4+3 has the worlds WORST linkage.

bogus

oh, I remember one alignment setting trick on the 1987 and earlier cars.

swap the upper control arm mounts. The rear mount forward, forward, to the rear. This will give added camber.

however, since camber effects steering center, it may not help you at all.

astock165

I agree about checking out the AX&RR forum. There is a ton of info there but in short for alignment: max out the front so its even (probably about -2* max as the C4 is camber challenged) with a little toe out (1/8"-1/4" total). Put about 1/2* LESS camber in the rear with a little toe in (about 1/8").

I have to disagree with this one. My 93 coupe is an A4 and the although the auto may not be ideal you're probably going to be in 2nd most of the time anyway. If it's an auto, just put in 2nd leave it there.

Vetracr

From your description your building a BSP C4. From what you've described of your modifications you have a long way to go to be competitive with the Harold Olsens and Rita Wilseys of the world. The 87 is a great starting point. It has a better for autox suspension than the 88+ cars.
Suggestions;
1) Forget about the engine until you have the suspension dialed in and have experience driving the car.
2) Go with 84 Z-51 springs. 2nd choice 85-87 Z-51 springs
3) 30 mm front bar (minimum) and 24,25 or 26 mm rear bar. You'll have to test.
4) For starters try to find Corvette Challenge Bilsteins or Koni sports shocks. The quick BSP guys and gals are all running Penskes or other mega buck shocks.
5) The automatic is fine for autocrossing. My 86 Z-51 auto (w/3.07 rear) was consistantly 1 sec faster than my 90 6 spd.
6) Go with Hoosiers or Kumho tires. I can't stress the importance of running good tires that haven't been excessively heat cycled. You won't learn a thing about your suspension set up on old tires. Get the lightest wheels you can find.
7) Make sure you have the fast rack and a PS cooler.
8) Go with poly bushings everywhere.
9) Get a good drivers seat and belts/harness to keep you upright in the seat.
10) Front suspension 1.75 to 2 degrees negative camber. Mill the upper control arm spacers or use offset LCA bushings. Run 1/8" toe out. Caster, all you can get.
11) Rear suspenaion: 1.5 to 2 degrees negative camber, 1/16 total toe in.
12) Use VPB or Gulstrand rear toe assembly
13) Probably number 1 item. Drive the car as much as you can to learn a) how to drive it ans 2) to learn effects of changes you make.
14) Have an experienced Corvette driver test your car and give you feed back on how it handles.
14) Theres more, lots more but this is a start

Larry

DonF

Vette Brakes Mag. has a section in it for setting up alignment for Autocross, that what we use & it seems to work well. We also do switch the small donuts. Change out the rear rears & the auto will keep up w/ all of the six speeds. What are you autocrossing in? NCCC? Good Luck

xflagz51

Just for my own knowledge, why is the early suspension better for autocross than the '88+?

bogus

They redesigned the suspension in 1988, as a result of lessons learned in the Corvette Challenge Series.

however, the earlier versions were a bit more sporty, if you know what I mean. Essentially, more aggressive.

The later versions were better road cars, where the earlier versions were better track cars.

I know that's a generality, but it holds reasonably true.

When they redesigned the suspension, they did it all. Camber, caster, roll center, control arm & spring (front). The rear got some new geometry, too.

I don't know all the specifics, but this should give you a good idea.

It's also why many parts from the earlier style are not interchangeable with the later style.

Also, the later style got uprated brakes with 2 piston calipers.

z28cp

Vetracr -Not with this...

Rachels - The cam, rockers, and Ported and Polished heads aren't legal for BSP. Sounds more like an SM2 car with these mods.

My .02.

DaveZ.

Vetracr

Whoops! Missed that.

Larry

c4cruiser

Fortunately the Z52 cas has the additional chassis stiffeners That were used in the 'vert welded in place. That helps keep the front stiffer than a bse car. Also get one of R-D Racing's Camber Brace strut bars. They bolt right in and will help a bunch.

R-D Racing also has a neat product called a "Targa-Truss" that bolts into the factory holes for the coupe top. The factory top will keep the body from flexing, but the Targa-Truss lets you run with an open car giving you more head room (especially for the helmet) and keeps the body stiff.

The factory 11.5" rotors are not the best if you are going to do long and fast courses. But for now, get the cheap "white box" rotors and use a good semi-metallic pad like the Hawk HP+. There aren't too many good race level pads for the early cars so later on you will probably want to upgrade the brakes to the later J55 13" rotors or go with a C5 brake setup. This will require 17" wheels so you may have to balance this with the higher cost of wheels and other tires.

The Z52 rack is the same ratio as the Z51 but Z52 didn't get the cooler. The factory cooloer and lines are not available so you will probably wind up having to fabricate a small two-pass cooler and new lines.

I like the 4+3 in my 87 for autocrossing. Just remember to shut off the OD at the shifter when you stage. I pretty much try to get into 2nd gear as soon as possible. The L98 has great low-end torque and will pull the car hard at anything above 2000RPM.

xflagz51

Isn't it amazing that just a few years ago you could be very competitive with Konis, then Guy Ankeny started installing Penskies and now you have to spend $1200 a corner to be competitive on a national level.

Adam.

rocco16

Racing anything, from Corvettes to lawn mowers to belt sanders, is a competitive endeavor.
How fa$t do you want to go??

Kid, assuming your dad was 5th in the nation in autocrossing, it seems like you have a wealth of information in him that you could tap. Also, your post indicates that you are concentrating on power more than on handling or driving experience.
You are going about this backward; time/money spent on driving schools will yield returns far above time/money spent on porting and polishing. Next, get the chassis/suspension/brakes/tires sorted out.
Then and only then will additional power be of benefit.

Good luck and don't be surprised if the old man kicks your fanny for awhile....

Larry
code5coupe

xflagz51

It's a well known fact that there is no better teacher than experience or in this case, seat time. My Dad kicked my butt a couple of times. You're right, racing has always been a very competitive endeavor and it can be very expensive. I guess spending $5000 for shocks to win doesn't score too high on my scale of priorities.

AUTO_X_AL

if you are just auto crossing I may not upgrade to the big brakes. The bigger brakes are 7lbs heavier per side! I think the old rule of thumb is that every pound of unsprung weight equals close to 7lbs of sprung weight or non-rotational mass. I have know a few sm2 cars to run awfully well with the small brakes and this was on larger courses with alot of left foot braking going on. I upgraded the brakes so i could run the HT-10 hawk pad and have increased fade resistance becuase we opted to do some high speed courses that were very hard on brakes(gingerman mainly) but for auto-x I would stick to the small brakes because they are lighter.
If your going to be bsp you cant run half of the aforementioned stuff either. If scca is where you want to be get an LT-4 and a ZF-6 or use the auto because lets not forget an auto won BSP last year. So with an A4 and a decent rear end you could have a good car to run with. Best way as always is get a rule book and build.