The one big problem you will have at that speed in a C3 is air entering under the car lifting the front up. Your first priority is to minimize the air going under the car. The front airdam is crucial and needs to be as close to the ground as possible without touching.

Next you want a slight rake. Front down, rear up. Again your trying to manage the air that gets under the car.

You also need to properly secure the hood. There will still be enough air under the car to blow the hood off if it is not secured. Duntov had this happen to him back in the late 60's/early 70's.

 

Zwede, hehe...I been looking at them flimsey hood hinges for years now, been debating about pulling them and doint something differant, like maybe hood pins all 4 corners..?? dunno, gotta be stainless though....can't stand rust, guess from what I seen some years ago, I will have to make my own, did that on an old GTO/Lemans I had....maybe after the headlight project....

GENE

 

I agree, get ahold of gkull. He does alot of mile racing.

Something like this would probably help with some of the turbulence the car creates.

 

Check the Chevy Power Service Manual. Tonnes of info in it about go fast aerodynamics, body angles, suspension loading...

Lower it, tape over all the seams... hold downs for hood, windshield and rear deck window. Lexan would be good for the windows, you can steal from the drag racers.
Manage air flow through the radiator (ala P-51 Mustang) it is very draggy

Ditch the mirrors, NASCAR wheels/tires with inner liners are cheap, fill the rims with foam or aluminum flush with side of car. NASCAR does 200 all afternoon long on the super speedways (with open side windows) (not a fan) take a close look their setups.

Air dam can be constructed of 4" or 6" wide industrial rubberized flat belt like a conveyor belt at the grocery store only 1/4" thick.

Keeping air from getting under the car is good thing... you may have to put a spoiler on it to get enough rear downforce for traction as drag increaes. The C3 vette profile is like the first 2/3 of a wing and will generate lift if air flows over the top and under the car at the same time.

I assume you've studied the class rules and are gonna ditch anything that adds weight or is not involved with going faster or saftey.

Have you thought about steering stability and suspension setup. A damper may be in order to keep a check on any oscillations that may develop in the steering.

If it were me I would approach 200 mph in steps with a plan so you can find the edge without jumping off!! My experience (all be it with motorcycles) and only to 165 MPH (front straight at Pocono and Bridgehampton on a 1000cc in A Superbike in WERA and FUSA racing and with my current 500cc GP Replica bike up the back straight at Mosport at 143 MPH) anything high speed sustained needs practice to keep control and may require adjustment to deal with unexpected aerodynamic or chassis forces.

Replace/check every critical fastener/component in the suspension, steering, and brakes as a minimum unless you know the history of each, 20+ year old fasteners have no place at 200 MPH . Saftey wire ANYTHING that you dont want coming loose at speed.

Vibration Kills, Strain relief and abrasion proof anything you dont want a hole in and balance every thing you can.

And last but not least, buy some black nomex underwear, it helps hide the skid marks, 'cause if you aint scared your not going fast enough!!!

 

Very, very nearly stock-bodied C3 have been way, way over 200 more times than can be counted.

 

You need to put one of those ricer spoilers. This guy makes them out of cardboard great for civics aerodynamics at 330 mph

 

Gale Banks set the Bonneville worlds speed record for a stock bodied automobile that had no aerodynamic modifications. This was in the late 1970's or early 1980's. It was a Corvette. The run at Bonneville was over 200 mph.

The car that he ran was a 1968 Corvette Convertible hard top. It was a completely stock body. No wings.

We had a Corvette show at Champion Chevrolet in Manhattan Beach, Ca and Gale Banks brought the car. I talked with him about the car.

He said that the aerodynamics of the basic body shape were ideal and that's why he chose a Corvette. The hardtop/aero cutoff and the Corvette tail end/aero cutoff meant that the rear would not create lift at high speeds. He pointed out that the Porche 911S's of those years were aerodynamically more stable running down the road backwards. (Interesting that he made a specific point that the Porches were aerodynamically unstable.)

Anyhow, to run over 200 mph in a stock 1968 Corvette hartop convertible....you've got to have 1200 HP!. That's the HP that Gale said he was running. His car had a twin turbo 427. He said the engine could run in excess of 1500HP, except for the Bonneville run, he dropped it down to 1200 for reliability. Oh...stock bodied yes but underneath there were some other changes. The front radiator had heat exchangers for the turbos, but the water radiator for the engine was replaced with a big water tank for engine coolingl The water tank added 400 pounds to the front end of the car to keep it from lifting off the ground at high speed.

Bottom line here is that if you want to go really high speeds, you need really high HP because wind resistance increases dramatically at hight speeds.

 

Maybe it is just late and im stupid, but what do you mean by this?
"hardtop/aero cutoff and the Corvette tail end/aero cutoff"

 

Opps.. Sorry, you're certainly not stupid but I should have been clearer about what I was trying to say. The flat back valances of the chrome bumper Corvettes and the flat back of the Coupe rear windows and the Convertible Hardtop's basically create a lot of aerodynamic drag. However, this drag component, tends to make them stable at high speeds. This aero drag prevents the rear end from lifting up. For example, the Mustang version of the mid-70's. It had a large sweeping fastback body that approximated an air craft wing. Unfortunately at a drag strip someone running one of these cars was killed when the aerodynamic effects of the fastbody styling caused the rear end to lift.
Maybe someone reading this can remember the Mustang drag racers name.

 

high speed

 

You need to get the car as low as possible and keep all the air you can from going under the front. Duntov was finally able to get the lift down to 75 lbs at 100 mph. At 200 mph this is going to be 400 or 500 lbs of lift.

The underside of these cars are very aerodynamically dirty. If air gets under there it creates drag on everything. You will need a front air dam and side skirts that are only about 1/2" off the ground.

Also remember you'll need a VERY stiff rear spring. The more power you transmit through the rear tires the more the rear suspension will squat. Not only that but the more traction the rear tires have the more they try to lever the front tires off the ground. This is exactly why top fuel dragsters need wings on the back AND the front.

BigBlockk

Later.....

 

I have been at 187mph. The only front end work was smoothed lights and bumper and alum skirt under the front nose to seal off air going under nose. This is a drag car and I could change gears and hit 200 easily at the half mile mark.

 

what is the HP ???

 

The fastest speed I got was in my '76 Trans Am, changed it to a 4 sp man.(T-10) without changing the rear end gears, I did'nt know, I was young and learning. It was frying the clutch at take off, but at 3rd gear I was at about 140-150 mph comfortly, with one more gear to go ! Now in my '80 vette I'm scared at 110mph. Either the vette is too light or I'm sure I'm just getting old, or Both.

 

are you sure it was that fast ???

 

I believe the speedo was 120 max. and I was pushing Way pass that in 3rd. So, no I'm Not sure.I apologize.

 

I have the longer Daytona front end and I believe that it's much more earodynamic than stock. Here are some Vettes that I have taken pictures of over the years. I try to make it to Bonneville at least once a year.

Wheels and tires that fit the wheel and front air dam are very important. The rake of the car is how you balance out up and down forces front and rear.

200+ is attainable with just low 500 hp in the later year model c-3's




These sundowner guys go out with a dozen people every year and they all drive over 200 mph.

Then just get your gearing right - This is just a picture driving down a twisty road, but I have a 7500 rpm red line so I'm not doing half my rpm

 

Its over a 1000 conservatively.

 

gkull, whis is everyones exhaust out the front?

 

I think, since mufflers aren't required they run the shortest possible exhaust. No weight of pipes and muffler, none of the associated wind resisitance, etc.

As I remember, the Vettes that did well at Le Mans & the grand prix were convertibles with the hard tops since the hard tops had better aerodynamics.