'A straight-bodied, two-door sedan from 1967 for $2,000 that runs and drives? Sold. Our fantasy was to build a car and drive it solidly into the 10s because even factory cars are running 11s, and Car Craft hasn't had a really fast car since former Editor Matt King's Super Nova went deep into the 11s with a correction factor. We need to be faster.
With insurance cash in hand, we set out to buy the lightest, coolest car we could find. We apprehended a six-cylinder '67 Rambler American that we cobbled together in the May '06 issue and got running with gear from a V-8 Gremlin for a total of $3,500. It smoked its way down to San Diego for the Car Craft Anti Tour then lost oil pressure. We didn't care because we already had a plan.
Why 10s and not 9s? A quick glance at the NHRA rule book told us that 9s required a valid competition license and lots of expensive, SFI-approved goodies like a flexplate shield, a rollcage, and an unfashionable driving suit. We also found that if the car is full bodied and running anywhere between 10.00 and 10.99, you can get away with a rollbar instead of a 'cage. A 'cage requires a side bar on both the driver and the passenger sides of the car and a forward hoop that crosses between the roof line and the top of the front windshield. To us, the look of a 'cage draws the line between a street car and a race car. The 'cage is more complicated and expensive, and the rollbar is easier to hide and requires only one side bar that can be removable. According to the rules, a car with a rollbar cannot exceed 135 mph. So to give ourselves a little wiggle room, we settled on 130 mph as a top speed in the quarter-mile that should put us right around 10.50.
Gears, Mph, And Tire Height
After you've figured out how fast you want to go, you need to find the weight of the car and determine how much horsepower you'll need to accomplish your goal. The formula to estimate amount of horsepower for a terminal mph in the quarter-mile is: hp = (mph / 234)3 x weight. As an example, if your car weighs 3,000 pounds, you'll need about 500 hp to run 130 mph, and if your car weighs 4,000 pounds, you'll need about 685. This is simply a power-to-weight calculation, and experience has shown us it is a little conservative, much depends on the engines torque potential. There are a lot more factors involved in goin' fast, but this is a good place to start, and it shows why weighing less is better.
The next thing you need to do is find out where your engine will make peak horsepower and pick a rear gear that will put the engine at about 200 rpm above that number going through the traps in High gear. Here is the math: gear ratio = (rpm x tire diameter) / (mph x 336). This is closely tied to the size of the tire you are going to run, so before picking a rear gear ratio, find the largest tires that will fit under the rear. You should also note that an automatic transmission in High gear will exhibit about 5 percent slippage, so you will need to add that to equation.
If you've been following along, you know we pulled the six and showed you how to paint the
Instead of immediately frying the stock 904 TorqueFlite, we ordered a rebuilt one from TCI
We predicted the stock AMC Model 20 rearend would fail, and it did on the third run. It wa
The Rambler weighs 2,771 pounds, so we ran the numbers and came up with 461 for an engine-horsepower number. Adding a 180-pound driver and and 10 gallons of fuel at 7 pounds per gallon, the race weight is more like 3,021, so the horsepower required is closer to 483. We plucked a 360 from a Jeep Grand Cherokee, and with some Edelbrock heads, a flat-tappet Lunati cam, and 10.5:1 compression, we made 480 hp at 6,000 rpm in the Jan. '06 issue, before we dropped it in the car. We solved the equation using 6,000 rpm for the ideal trap rpm knowing that with converter slippage the final rpm would be about 6,300. We plugged in the the 26-inch-tall tire, divided it by 130, and got a rear ratio of 3.57.
The Rambler's design restricted the tire size that will fit under the rear without either installing minitubs or relocating the springs. With the 15x7 rear rims, the tires are within 11/48 inch of the springs, and we had to trim the inner fender to get the tires to stop rubbing. The biggest tire we could get in there was a 235/60R15 that is only 26 inches tall. A larger tire, like a 275/60R15, has an overall diameter of 30 inches and would allow us to run a 4.10 ratio. Since gear ratios multiply torque, the higher numerical ratio would help the Rambler run a quicker 60-foot time. More tire allows more gear, both because the greater footprint would help traction and the increased height would still keep the trap rpm where we want it.
We have the weight and we have the horsepower, but for the first three runs, we used the stock 2.71 rear gear. The result was a baseline of 12.75 at 112 mph, which is exactly what Comp's Desktop Drag said it would be and about 2 seconds slower that the pure power-to-weight math wanted us to believe. The run pointed out that the small tire might be enough if we don't hit it too hard on the line, and we are definitely going to need a better gear ratio if we want to go fast. Knowing this, we are going to try a 3.55 gear with the small 235 tire before we return to the racetrack and see if we can go fast without cutting the car for minitubs.
|PARTS LIST |
|DESCRIPTION ||PN ||PRICE |
|'67 Rambler American ||N/A ||$2,000.00 |
|Engine total from Jan. '06 ||N/A ||7,296.11 |
|ADDITIONAL PARTS |
|TCI Torque Command 904 ||601100 ||1,009.00 |
|TCI 10-inch StreetFighter || 751600 ||432.88 |
|Transmission dipstick ||22160 ||74.02 |
|Royal Purple transmission fluid, 5 ||N/A ||8.95 / quart |
|Exhaust Labor ||N/A ||100.00 |
|FlowMaster U-Fit dual kit ||15936 ||183.39 |
|Flex-a-fit radiator ||52180R ||899.95 |
|Powermaster Ultratorque starter ||9415 ||229.95 |
|Stockton Wheels ||15x5 and 15x7 ||440.16 |
|M/T ET Street and VW front tires ||235/60-15 and 165x15 || 411.90 |
|PAINT AND BODY |
|Total from Dec. '06 || ||645.40 |
|TOTAL || ||$13,767.51* |
*Low 12s on the motor in a reliable car that isn't a Chevy. Send rants to CarCraft@primedia.come.t.Corrected 12.36 at 115.36Uncorrected 12.75 at 112 mph
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We weighed the car and found that without the driver, it was 2,771 pounds. The heaviest co
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