Final Drive Ratio Thoughts

[grubby65]

I am getting close to installing the new motor in my Polara. Just waiting on the Dyno Tune and we are ready to go. The motor is a 400/499, Aluminum heads, roller cam, roller rockers, etc. I don't have the final numbers from the dyno, but the computer says the motor will do 500 hp @ 5000 rpm, but due to the cam selection it really noses over above 5000 rpm. The torque is 620 @ 4000 rpm, but carries over 600 #'s from 2000 to 4000 rpm. Currently the car has 4.10 gears and 285 -70/15 tires (30.75" diameter). It is not tubbed, but as you can see the rear of the car is pretty high to keep the tires from rubbing. The car will mostly be street driven, but we do have local drags (non-competitive) and I will probably take it there 5 times/year. I'm planning on a tire change (either 255/70- 15 or 265/70-15). The question I have is what to do about the rear end ratio. I think the car should run between 110-120 in the 1/4 mile. Would you design the final drive ratio to be around 5000 rpm at 120 mph or would you do something different?

Any thoughts would be greatly appreciated.
Thanks

 

[mmissile]

Tall tires kill a bunch of that gear. I'd run it, and see hoe ya feel about it. Actually running the car and gathering info, is the only way you'll really know.

 

[HEMI-ITIS]

Then try a shorter tire,,,,,,

 

[lewtot184]

a flat torque curve with moderate rpm for peak horsepower won't need a bunch of gear. a 3.55 with a 28" tall tire may surprise you. a friend of mine went 11.60's/120mph+ with a 508, 3.23 gears, stock cast exhaust manifolds, and a 4150lb charger. big torque engines are handicapped by low gear ratios.

 

[cryplydog]

I have 4:10 d-60 and 4-speed in my 64 440 and with a 512-B. It's been fun but the thrill is gone. I'm going to change to the 3:53 this year and the car will be a lot more fun, for me.

 

[dvw]

Leave it alone and test with what you already have. To many variables at this point toake an accurate decision.
Doug

 

[HEMI-ITIS]

Leave it alone and test with what you already have. To many variables at this point to make an accurate decision.
Doug

Must start somewhere.

 

[SUPERSTOCKRACER]

What size cam is it the motor?
I think a 28" tall tire would be perfect with that gear ratio, i'd like to see you cross the stripe at 6000

 

[HEMI-ITIS]

119 or 88 all the way!

 

[Mike67]

Badass looking car!!!