suggestions for rear gear ratio?

[orange cuda]

VERY new to the forum, and just getting back into performance cars. I would like suggestions for R. gear ratio for my 3020lb. 74 Cuda(fiberglass parts). I believe at the present time I have 5:13 gears. At 55 mph I'm at 3000rpm. This is with 33 inch tall tires.(Mickey Thompsen Sportsman 33X21.50X15) Car seems to have plenty of power off the line, and or not much traction. 440ci.,lumpy cam?, TorquerII intake,850 Q. Fuel carb, and 727 with 3500 stall. Not going to be a hiway car, just cruise nights, and some informal 1/4 mile racing.Right now it doesn't seem like I'd have enough RPMs to make it to the end of the 1/4 mile.

 

[moparleo]

http://wahiduddin.net/calc/calc_speed_rpm.htm
And
http://www.wallaceracing.com/Calculators.htm
Save these for future reference.:homework: Have fun with them. Lot to learn from these charts.

 

[orange cuda]

Thanks for the quick reply, and the links. The Wallace racing calculators are easy enough for even a D.A. like me! I'm thinking 4:56 at this point. Any tire recommendations for something street legal with some bite that won't break everything? I would prefer the tires to be the weak link!

 

[moparleo]

Remember that lowering your gear ratio increases engine rpm but slows tire rpm. That way the engine is at the top of its power band at the launch. That's is why a 4:56 will hook when a 2:73 will just smoke the tires. That is why when you watch the drags and any of the non nitro cars do their burnout to heat the tires, they do it in second to third gear to get the tire speed up. You want the car to be reaching its peak rpm as you go through the lights. You need to determine what that engine rpm is. Some chassis dyno time. Once you have that info you can calculate the tire diameter and gear ratio to get you where you want to go.

 

[burntorange70]

Another good thing to have is the Mopar Chassis book. It walks you through stuff like that. Can get it through Mancini racing and other places like that.

 

[Chryco Psycho]

The ratio I found worked well was a 4.30 :1 I went through the traps @ close to 120 MPH , the 440 makes lots of torque & will work well if it is not allowed to rev too fast .