zdave83

Hello,

I'm going to do my first HPDE event this spring, and my C3 is bone stock. Looking for advice on the top 2 or 3 things I can do to make it safer and perform better at the track. Here's what I have so far:
1) change 225/70/15's to 255/60/15's
2) put on a set of adjustable shocks (brand?)
3) change 2.73 rear end to 3.55

Thoughts?

Thanks - Dave

wallyman424

be careful giving your car more grip. I dont know anything about C3's, but if youre putting more grip on a car with a soft suspension, you could end up with a big handling problem.

basically with that car, i'd be much more concerned with the brakes than anything else. fluids/pads/rotors/calipers/lines all that stuff.

CHJ In Virginia

I agree with Wallyman ---- the very first thing to do is get your brakes up to snuff. Stainless lines, High temp fluid like ATE or Motul and a much better set of pads. Unless your tires are well worn - run with them for starters and adjust pressures. The biggest improvement will be the driver --- seat time --- seat time --- seat time --------

AU N EGL

with Wallyman and CHJ

Do the brake fluid and brake pads first. Get an event or two under your belt before HP or tire mods


Good Luck and let us know how it goes

NASAblue

brakes! 82 c3, does it have rear rotors or drums (not that familiar)?

What tires are currently on it? How old are they are they dry rotted or suspect? They are radials right....

Find out what supension you have too, some of those came with performance steel transverse leafs and some came with composite fiberglass leaf I think. I want to say the steel was the high performance option but I'm not 100%, I'd have to look it up.

If those are the stock 26 yr old shocks that should prove interesting....

What engine do you have? L82? with a 4 spd?

rfn026

Keep it stock for the first year. You'll spend enough money on the brakes to keep the Visa people happy.

If you buy adjustable shocks who's going to set the shocks up? Adjustability is nice but don't forget you can adjust yourself right into stupidity. (I have a lot of experience with this.)

Just focus on your driving and maintaining the car. If you decide you like driving fast you can make the changes next year.

My advice is always "Just drive the damn car."

Richard Newton

How to Restore and Modify Your Corvette, 1968-1982

Wheel and Tire Performance Handbook

WNDOPDLR

First and foremost- welcome to the dark side. I am in agreement with the others. I have instructed in a C-3 and they are pretty capable cars. I will pick up on AU N EGL's normal mantra of seat time, seat time, seat time, before you spend money on the car. Having said that, do a better than normal check on the car. Look at brakes and lines as others have said. Make sure your tires are in good condition. Take a hard look at suspension components like rubber bushings for dry rot and brittleness. You will have your hands full for the first few events just learning your car in a different capacity and at a different level than you have ever done before. As Wallyman said, the change to different tires opens up a whole set of issues like shocks, springs, bushing, etc. and should not be done in isolation.
One thing you might do that is inexpensive is to take along some throw rug anti-slip mats. They are sold at the big box -Lowe's etc.- in the carpeting dept. They go under throw rugs to keep them from sliding on hardwood floors. C3's have old slipperery seats with no bolsters and you will have a hard time maintaining your seating position. Get two. Sit on one of these and it will help keep your butt in place and then give one to your instructor. He will love your thoughtfulness.

Good luck, have fun, relax, enjoy and let us know how you liked it.

bb69

As the others have said, start with the brakes. I use Hawk HP Plus pads, stainless braided lines, and Valvoline synthetic fluid. That combination should do just fine for your first year of track events.

For any C3, you should carefully inspect the rear trailing arms and hubs to make sure they are in good condition.

Something else to consider is putting in a real seat. If you seat is anything like the seat in my 69, you will be doing everything you can to hold yourself in the seat. There is no way to be smooth and consistent when you are sliding all over the place.

Check you suspension bushings and replace them if they are dry and cracked. Also, inspect the front lower control arm mounting brackets. This is a known weak spot. For more information, look in the C3 Tech section for this subject.

Overall, you will be surprised what a C3 can do on the track. I don't think you will run out of car during your first year.

Good luck
Ken

zdave83

Thanks for the time everyone took to respond to my question: brake system, seat time, rear trailing arms, front lower control arms, general condition of the suspension, and later a balanced approach to upgrades. Got it!

In answer to the questions above......
o 4 wheel disk brakes
o new 225/70/R15's
o I believe that all 82's had fiberglass monoleafs
o engine is an L83, with 4spd auto
o will get new shocks, adjustable to accommodate upgrades later
o later C3's have fairly supportive seats, but I'll give the anti-slip mats a try

Thanks again for your help! Dave

Gordy M

Couple of suggestions: get a friendly alignment shop that will mark two alignments, one for street and one for HPDE. The street alignment is what you currently have, the track alignment would be 2.25 deg neg camber, 0 toe in rear and 1/16 toe-in in front, all the caster you can get. Sometimes you have to get longer rear A-arm bolts to get all that camber.

That set up will make a tremendous difference on the track.

Inflate the tire to 44 lbs front and 40 lbs rear.

Get the 65-67 Big Block w/o air front springs, they will put the front end lower about 1/2 in.

Put the steering tie rods to the fast turn position if they are not already there.

That set up worked well for me with my 64--except I had the famous drum Z06 drum brakes

DREGSZ

Well I see we have some knowledgeable, and some very not knowledgeable C3 guys here.
Glad to see the Seat Time Mantra is starting to sink in.

Corvettes got (the J56?) 4 wheel disc brakes in the mid sixties.

Certainly track pads and upgraded brake fluid is a good Idea. there is nothing wrong w the C3 calipers.

THe one suspension Item I would SERIOUSLY consider changing, (even for driving in the street) in a C3 is a lower rear toe bracket.
Guldstrand used to make a drop braket w hard or no bushing for this piece.
the reason is the rear diff "jacks" in a C3 and variably changes the rear toe angle in different parts of the turn.
Personally, I find this kind of scary

Maybe called camber bracket, not finding the correct link.

E

DREGSZ

called "smart strut" from Vette brakes and performance
PN 52000HD

Jason Staley

I've been to a few HPDE's with my C3 and here are a few things that will make your car drive more predicable and safe:

1 - Like others have said, change the brake fluid to a high temp. type
2 - Change to a "smart strut" rear camber bracket and set the inner point to the highest setting, then adjust the rod length to set the camber. This will reduce the jacking, but still give a decent camber curve. Another option is to make a 1/2" aluminum block to lower the factory bracket (cheaper but more work) .... oops I see yours is an 80-82... the aluminum block trick won't work on yours.
3 - Have a very good alignment done. C3's are very sensitive to the alignment because of their suspension geometry.

One thing you'll have to contend with that the newer corvettes don't is serious bump-steer from the front and rear suspensions. Its not easy to fix this characteristic but a few things during the alignment will help reduce the rear bump-steer and make the car more enjoyable to drive.

First of all, if at all possible, make sure the rear half shafts slope downward slightly from the rear end to the wheels. This will help reduce the bump-steer effect. You definitely don't want the half shafts to angle up to the rear wheels. Second, when the rear toe is set during the alignment, put a little extra toe-in (like 1/8"). This will help keep the rear tire that is loaded in a corner from toeing out resulting in oversteer at just the wrong time. The bump-steer issue can be improved more, but it takes a bit of work (i.e. moving suspension pivot points). They're covered over in the C3 technical section and you don't really need to worry about them on your first time out. Just get the alignment set-up good and you should be in pretty decent shape for a fun day.

zdave83

LOTS of great advice -- thanks guys !

Mike's 68

Order yourself a Vette Brakes & Products (VBP) Catalog:
http://www.vbandp.com/pages/vbpmaillist.aspx

They have various performance suspension packages and brake products and their catalog is very helpful, even if you don't buy anything from them.

For my 68 I've replaced the front bushings (poly), the front anti-sway bar (1 1/8"), the tie rods/tie rod ends, the idler arm and all four ball joints and all four shocks with Bilstein sport shocks. Now I'm finishing up replacing my rear drive axial’s u-joints, trailing arm bushings (poly), adding a rear anti-sway bar (3/4") and adding smart struts. Oh yea, I got the stainless steal braided brake hoses yet to install.

I completed the front end work last summer during the autocross season and it helped a lot. Actually it was the highway driving to and from the autocross that it help the most, it’s not as scary as it was before.

Bill Dearborn

I had 69 and 71 Big Block daily drivers but haven't played with a C3 in over 20 years. Not knowing the history of your car there are a couple other things I would check. If it has a fair number of miles and was driven in the rain a lot in the past I would check the frame for rust in the box sections in front of the rear wheels and at the top of the bump just over the rear wheels.

Also get the radiator checked and make sure it is flowing coolant through all of the tubes. When inspecting the suspension bushings give the upper front A Arm bushings a very close look as exhaust heat can cause them to fall apart. The rear trailing arm bushings can also take a beating and while you are inspecting them inspect the arms for rust through.

If you have silicone fluid in the brake system you could have a problem. Silicone is great for a garage queen that isn't driven much as it can prevent rust in the caliper cylinders which then causes fluid leaks. However, silicone fluid isn't any good on the track as it tends to out gas when it gets hot and you can lose your brakes. The problem is once you have silicone fluid in the system it is next to impossible to get out.

Get the transmission oil and filter changed if it is an automatic (were all 82's automatics).

Get new seat belts. I wouldn't use 26 year old belts in any car but a lot of people have them in their old Vettes. That many years can lead to a lot of sun damage and seriously compromised belts. If crap happens you want a belt that will stay together and not tear when it is needed most.

Bill

DREGSZ

My suspension Guru is Herb Adams, (everyone needs there own guru) he literally wrote the book "chassis Engineering" and was involved in the development of racecars for GM's
International Race of Champions program.

It didn't hurt that hs son Matt, raced and built his dad's parts for A Sedan Camaros (Racing Camaros were my springboard into Racing vettes) and they lived the next town over (Monterey Area) We used to hang out in the paddock at Laguna on raceweekends and talk what else... Racing...

http://rides.webshots.com/photo/1157...50964049haAYMC

http://rides.webshots.com/photo/1157...50964049JOGpqI

Anyway, Herb said that Poly is the wrong material for trailing arms because, (if I remember correctly) it binds and to stick w rubber trailing arm bushings.

I did in my 74 Hyd roller, 468, 4 spd, side pipe coupe w full road race suspension, let me find a pic...

I bought this car as a stolen and stripped roller, L48 auto, I replaced every nut and bolt in the car, etc...

most people know about big red in my avatar but never knew about my hotrod, "Whiplash"

http://rides.webshots.com/photo/1163...50964049AnYJJa

http://rides.webshots.com/photo/1163...50964049XiRMQM

The unmuffled side pipes kept this car from ever running at Laguna
My neighbors hated me too.

My newest project, Back to Camaros...

http://rides.webshots.com/photo/2974...50964049dMipbz

E

Mike's 68

I have a copy of three articles about how Herb Adams improves the handling of C3 corvettes to include his "Corvette Handling - A Performance Handbook" and you're right about the binding issue. He liked nyliner bushings, but unfortunately I can’t find those for a corvette, so I went with poly. When using poly (front or back) the trick is to use the lubricant that comes with the bushing (at least VBP provides lubricant) and to use lock tight to prevent the nuts from backing out.

Even though the articles are dated they are very helpful.
Small world!

69autoXr

Unless I'm mistaken, smart struts or lowering the strut bracket doesn't help the rear bump steer problem at all, it just changes the camber curve-to one which reduces camber gain, not necessarily desirable when you're turning left and right.

To what are you guys referring with the term "jacking"?

DREGSZ

Not sure of the correct terminology but I can sure tell you what it feels like
It seemed to me in my BBC C3 that the tighter the rest of the suspension, bushings, shocks, spring rates and bigger the sway bars the greater the exageration of wt jacking or the propensity to oversteer at the turn apex.
Jason Staley described it as a Toe/alignment issue, but the C3 racecars I have seen set up for and winning GT1 used a rod ended or solid version of a smart strut.

" Second, when the rear toe is set during the alignment, put a little extra toe-in (like 1/8"). This will help keep the rear tire that is loaded in a corner from toeing out resulting in oversteer at just the wrong time. "

I tried to call Matt and see if he wanted to weigh in on this subject and I they had a source for the bushings but got no answer. I don't know if they are producing vette parts, I always called them for Camamro suspension parts and bushings etc. but here is the contact info:

Matt Adams / VSE 8 Via Contenta, Dept. KC Carmel Valley, CA 93924
(831) 659-7660 www.vsecobra.com

Interestingly, if you check their site, they build AL. back bone frames for kit cars as laid out in Herb's book. but they also have the jigs to mock them up for corvettes and have a few finished ones laying around the shop last time I checked. THey were used for laying out the Avanti 2 chassis geometry which Herb did, (as I recall)

What this means is you can buy a frame, with various C4 components included and build a fully custom corvette, have it be super rigid, stong and light, and the finished project w body, roll bar and Iron block, AL head motor would weigh in at under 2100#s, even less w an LSx motor, Hmm, vette power w Lotus handling, Hmm
This would have been the ultimate street/track roadster w either a C2 Grand Sport Body, or much easier, A C4 vert body, now I have a line on C5 Carbon panels to make the car even lighter, or a C5/6 GT1 race car body would be very cool...
I almost pulled the trigger on this very project but at the last moment crashed my AIX Camaro and built C4R "Big Red" instead. Racecars come before food when you are in it.