Rear end gear ratio
 

Need help on setting up rear gear for big willow. Running top loader with 347 shift points 6500 max? any ideas

Welcome to the forum stidigs.
What's 'big willow'? Does that mean you want a rear end ratio for pulling out big stumps?
Cheers,
Glen

What size are your rear tyres?

What rpm would you be happy cruising at 55mph?

4:10 would be nasty:D 3:75 would be nice...%/

Little more info needed
 

stidigs First welcome to the club.:D We need a little more info for this question.
1 Guess how much torque and HP does your motor make?
2 Size of tires? Type? Wear thread?
3 Suspension upgrades? Driving on the track and cruising have 2 different suspension setups. If you re just cruising around the track, no problem. If racing, a whole different issue. If you are going to the track, you need safety equipment, helmet, gloves, firesuit, arm restraints, headlights need to be taped, battery tied down and doesn't move, cutoff switch for power. There's a list. You may have to run the car before an inspector for this. They should help you and explain what you and your car have to have to pass. A big one, NOTHING loose to fly out of the car onto the track. No leaks of drivetrain. They take your work on this.
4 Don't get mad:mad: do you have time on a track. need to know flags. Riding or driving with a instructor for the first couple of times is a good idea.
5 Speed, DON'T get crazyout there. Cruise in the back of the pack until you learn the corners of the track. Big one here, Brakes depending how hard you drive the fluid will get hot and the brake will fade. This is one thing that is different between street and track.
6 Over fill the motor by 1 quart. This will help save it on higher "g" turns. Against this is a street motor. Lossing oil pressure pull up to "1G" happens and will kill the bottom end bearings.
7 Safety check on your own, put car on jack stands and start from the front and work your way to the back of it. Check tightness of every nut and bolt you can get to. If you have pin drive wheels, they need to be safety wire tied. When was the last time your front wheel bearing where repack if your car has these? Chack play on all 4 wheel. no more than 1/8" upper to lower movement, same for side to side on wheels for front end parts like tierods.
8Last not trying to be a pain but seen too many guys think their cars can fly around a track without any issues and end up into walls, hit barriers, spinouts, tire assemblies come off, and burnt. We are not Nascar. Just guys wanting to have some fun with our cars.
9 Last side note, your insurance on both you and your car is no good on tracks.Check into this. Have heard and seen this happen with accidents. If they find out you where on a track, it could get real ugly.%/ Good luck, drive safe. get a wider rear view mirror for the track to see guys flying up on you. You want to give the pass by signal. This is optional, spare pair of underwear after you do your first spinout.:eek::o It happens to everyone.:rolleyes:%/:) Rick l. Ps wide or close ratio top loader??

gear ratio
 

More info. I am in the infancy stages of this build. motor will be 347, hoping for 400 to 425 torque. I am running a floater rear end so changing gears for street no problem. tires? running 15 inch rims, want to keep nostalgia look. guessing 26 inch tall. I am trying to fit the wilwood 6 piston 12.19 rotor under the front of this thing. have forged narrow dynalites for rear. Thanks for all of the input.

This is going to be an open track day car along with street use. I race a modified on dirt, but have no time on road course with a car, plenty in a shifter kart, but I dont think that counts

Willow is big
 

stidigs Going to need a first name here.%/ If you are running the big track, you are going to run out of motor or gearing. Thing about a cobra is once you hit the 110- 120 mph it becomes front end light. Mine at 125 wants to lift off. Have to remember that a cobra is a barn door cutting though the air. If you want a track car, build one and drive it on the street. IMO don't try the other way around with street suspension. With a 4 spd you have a limit problem for gearing. Either hit the rev limiter on the front straights or not get up to max rpms. 3.20-3.40 gears will get you around the track. You didn't say what the trans ratios are. If a wide box 3.20's. I run 3.31's but have around 600+ torque in my motor and limit to 6,200 rpms with many oil modes. HVHP oil pump, 3 quart accusump, system holds 13 quarts of oil. Always have min of 35 psi on high "g" turns. If nothing else, get a 3 quart accusump and add to oiling system. On the track you need to change the coil springs and add about 150-200 high spring strength. Drop the car down to about 3.5" at the lowest frame or point. Mine is the bellhousing. It's lakewood and I didn't modify it on the bottom. Nose down about 1/2" front to back. Have the car's corner weights done with your weight in the drivers seat. This will get you started. Alignment will be adjusted from the tire heat readings over time. Big brakes, need big air to cool them. I started with 15" wheels and 12.2 rotors and pads. Hard track driving causes Major heat build up and boiling of the fluid. Need blower fans and ducting to help control. I went to 17" wheels. 15" are great for drifting the car and give a better feel for when the car is coming loose. 17" better handling, but no warning of coming loose. Yes 3 spinout and change of underwear:eek::o. Need more air to rear brakes if they are inboard. Still need air to outboards. Look up the original cobra ducts for racing. They will give you ideas about a setup for your car. Good luck Rick L.

Turning your Cobra into a race car is costly and may take away all the fun you have on a daily basis. Just driving it on track day might be a better option. You know about racing and crashing and breaking parts. Count on it with the Cobra. Leave racing to your race car. That's what I do. If not, listen to Rick.

At Willow with the long straight, Small block and 26" tire I would choose around 3.70. With 1:1 Final trans gearing you'll be near 135 at max revs which you may not attain, but gearing will be good for balance of track. JMO