Thread: 1970 Ford Maverick

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If you build the car to run 11.50 or slower, you won't have to put a roll bar or roll cage in it, you won't need aftermarket 5-point belts and you won't need a fire jacket. These items can easily add up to more than $1,000, so if you can live with mid to high 11's, you can go out and have some fun for cheap.

Leaf springs will work, no need to back-half the car with ladder bars or a 4-link. Use an anti-rotation device such as Caltrac bars, Lakewood slapper bars or whatever to prevent spring wind-up. Use a bulletproof rear such as a 9-inch from a Bronco (narrow) with a set of gears to give you a terminal speed through the eyes of about 120 mph (1/4 mile). For instance, 6,500 rpm's with a 4.30 gear, 88" circumference tire and 95% converter lock will give you a trap speed of 119.67 mph.

Enter the maximum rpm's you want the motor to turn into your calculator, divide by the rear gear ratio, multiply by the tire CIRCUMFERENCE, divide by 1056 (the constant in the formula), multiply by the estimated converter efficiency at the big end.
(6500/4.3) x (88/1056) x .95 = 119.67

If you don't want to spend the money for a locker in the diff, you can run it as an open differential and make it work well by installing an air shock on the right rear only and adding air a little at a time until you get the right rear of the car pre-loaded so that you get two equal length black stripes on the pavement. It works.

I always advise those who are starting to hot rod a vehicle to start at the rear of the car. Get the diff all set up, then choose a converter to coordinate with the cam you'll be using, then start work on the motor.

To find the CIRCUMFERENCE of your tire, go to a fabric supply store and buy a cloth tape measure. Inflate the tire to the running pressure and tape it. You can convert diameter to circumference by multiplying diameter by 3.14159, but if you want bulletproof, tape the inflated tire.