I need to covert to a Ford 9" rearend so that I can run a 2.50 gear
in my Bonneville Car.

Any drag racers out there that have made the conversion to a striaght axle?

 

http://forums.corvetteforum.com/c4-t...sion-kits.html

http://forums.corvetteforum.com/drag...-axle-kit.html

 

http://forums.corvetteforum.com/c4-t...cs-inside.html

 

I am currently selling a very nice bolt in kit which several forum members have aquired. The kit is completely bolt in and does not violate the car in any way. Addresses the crossmember required and so on.

please email/contact me for more infromation

 

Dave, Have you considered picking up a dana 36 (out of a automatic c4) with 2.59 gears in it? You can find them cheap.

 

Good thougth, ragtop, yes I have considered this, but I am worried about showing up with either two much or two little gear, and no way to make the adjustment. I posted a wanted to buy for a D36 2.59 and got several responces.


the Ford 9 has a large amount of available gears.

 

Ski it down,

email me dhleb@cebridge.net

 

What are you doing to make your car ready for the salt?

I have always been interested in top end racing and was thinking about building a car for it.

What top speed are you going for?

What engine and engine mods?

Are you modifying the front suspension? What about roll cage and such. What tires and wheels?

Any info would be appreciated.

Craig

 

We are converting our 88 to a 9 inch rear for the same reason (running at Bonneville). You must be pushing big time torque and horsepower through it if you plan on going 220 or so. It's gunna take some big numbers.

What final trany gear are you planning? 1:1? thats what most guys run, very few overdrive setups - although I think running an 0.96 or 0.92 would work - but getting into 0.76, 0.82 - something on those lines - you just can't overcome the drag. Well you can - but it is expensive!

Carl Johansson

 

Craig
First of all - anything you know about drag racing - just forget it. Everything is backward. For tires - thin is in - 4.5 inches wide for most vettes and pumped up to 50 or 60 psi and they need to be tires rated to 250 mph -
traction on the salt is an issue - so you would think wide tires right? but if you had a table and sprinkled a thin layer of salt on it - and took a 4X 4 piece of plywood and put 50 lbs on it - it would slide easily when you pulled it correct? but if you took all that weight and concentrated it on a 1/4 inch square - it would be alot harder to move! - so tiny contact patches are essential.
for the same reasons weight is good - most record setting cars are carrying 500 - 2000 lbs of ballast to give better traction! I think the record holding vette comes in around 4000 or 4200 lbs.

Roll cage is complete - minimum 6 point - you need 2 separate fire systems - 1 for the engine bay - 1 for the drivers cabin. You need a parachute system - and a race seat and an SFI 20 fire suit.
Most guys running vettes use a coil over or airbag system of suspension

engine is your choice - you are classed by engine size - so you could run 200 CI or 600 CI or anything inbetween, different records for each class.

Current record for GT (unaltered body) C (engine 325 - 372 CI) is right around 230 (sorry the numbers are not exact - I can't find my rule book right now)

When you do the gearing and HP calcs for certain speeds - make sure you pay attention to wind resistance - as that becomes the 800 lb gorrilla as soon as you start to approach 200 mph - By my calculations (using a tried and true formula) for a C-4 vette - with a frontal area of 19.2 sq feet (I'm working from memory - I did this calculation 3 years ago - it was posted here in the forum - if you can find it) and a CD of . 32 It looks like - assume you are geared correctly - you need right at 500 - 510 hp - at the rear wheels - to go 200 mph.

Carl Johansson

 

Hi, Carl, Craig. but if you lower the car say 1/4 off the front spoiler the CD drops to the low .2's its all about frontal area, and CD. these two things impact The HP requred big time. you can't change the body at all so all you can do is work on the profile and try not to add any drag. At 372 CID for the top of the C class, there is only so much Hp you can make, so limiting the drag is the biggest issue. IMO.

I am running a LT5 looking for naturally aspirated 675BHP, and 575 RWHP. running the ZF6 in fourth at 1:1 and 7500 rpm. The key to my effort is I will not be altering the hood, no scoop required with this Lotus engine design. I plan on carrying 800-1200 lb of lead, depending on what the wind tunnel data indicates. look close at the front licence plate area of the number 42 car below, that stack of gray is about 300 # of lead.

this is the current record holder in the C/GT class at 230.5 mph

 

Lowering the nose is good, everybody runs nose low butt high - - not sure where you got the lowering of the CD to the low .2's. Thats a tremendous improvement. Do you have some source for that Data?
a 1/4 inch off the deck? how are you going to keep it from digging in as air pressure pushes down and bumps hop up? I'm looking at about 1 - 1.5 inches off the ground. Are you planning on using airbags or coil overs up front to lower it? I don't think the stock suspension will allow much lowering.

brian Cunningham put me onto a cad model site - and I think I can get this thing into a pretty sophisticated aerodynamics program and take a look at Angle of attack and lowering etc - to get a better idea. I'll keep you posted on that!

Not altering the hood will be big - everybody else runs a big old hood box - they do need the room for Intake stuff - but it sure looks like they are actually using the box to aero advantage - it does not raise the CD - and it looks like it smooths the transition from the hood to the cabin, and maybe dumps a bunch of air off the sides.

One of the places where aero improvement potential is big is under the car, but GT rules limit you on panning etc.

Good luck to you

Hope to see you on the salt. are you aiming for 09?

Carl

 

Carl take a look at the Calloway 1993 calloway CR-1 and 1990 Calloway Turbo both have a CD of .260 with no mods to speak of to the front, most of it is from , lowering the nose. And car 913 did a fantastic job with the hood design, regarding CD, But it adds to Frontal area big time. They probably increased the frontal area from the stock, 19.28 sq ft/ tp 20 or 21. Frontal area is the largest part of the wopper part of the math.

Mine will be running coil overs, and will be locked down on bump stops at the bottom. I am using the George Potets Blow fish as my basic model, keep it low front and rear. You have two choices put the *** in the air for downward force and more drag, or lock the *** down, and put lead in for the same downward force.

This is my basic thoughts and plan, hope it works!!!

whats your car #, maybe I've seen ya,

Dave

 

I want to hit Bonneville after the blower's installed.

I'd like to run a little downforce so I don't do this

or this

 

yep, lead is your friend, and so is a good set of 4 point scales to ensure the car is set up right.

Spins happen for the following reasons: poor car set up, poor driving, Wrong tires for salt ( both cars in the videos) bad luck, hit a rough spot, bad luck, caught a crosswind.

the spreadsheet below calcs Hp need, 550 at the rear wheels for 232 mph in a stock c4 . 550 in the rear wheels is pretty tough to do at a Density altitude of 7000' above sea level. But look at the very bottom, which calcs the weight required to deliver power to the wheels. pretty big numbers

 

Thanks for the info.

Are most o the cars running standard trannys or automatics?

Are you making any changes to the front suspension?

 

man, I wish I had more bar so I could get out there. I have the belts, fire system (well, the engine one) and plenty of motor. This stuff sounds fun.

I wouldn't mind hitting the mile sometime too.

 

He pulled the chute at least.




Hey Dave why dont you buy my Z and beat it up at the flats? Spare motor, too .

 

Cause, I allready bought a high mileage 1990 ZR1 Off ebay, that I am using as the donor car.