Expect to see even more power in Extreme, as the engine rules are rather liberal. Forced induction is legal, for example, but Ryan says, "I haven't seen an aftermarket power adder that can stand the rigors of a 40-minute race at 110 degrees in the desert." As the class stabilizes, we expect to see maybe 500hp naturally aspirated small-blocks combined with well-sorted chassis carrying the day.
To support the power increase, Extreme cars can run any size Toyo RA-1 they can fit on a 17x9.5-inch wheel, and somewhat more liberal fender-flare rules are given. Frankly, unless you are a seasoned racer and have a penchant for taking overall wins, we'd definitely stick with American Iron as you'll spend less money, more time racing, and less time monkeying with engines.
But in any case, we certainly urge you to get on track and go for it.
Not Just Late-ModelsAmerican Iron is open to any American-made, rear-wheel-drive sedan certified by the Department of Transportation, with a 100-inch-or-greater wheelbase and using a live rear axle. That means all sorts of cars are legal, such as a Dodge Charger. More to the point, early Mustangs (and Camaros) are welcome. At press time, no '60s-era Mustangs had made it to the track, but some were reportedly under construction for the series.
Too Much Power?With a power-to-weight limit, it's possible to have too much horsepower. Just ask Ryan Flaherty. When preparing his American Iron car, he came in with 331 hp and just 2,970 pounds of car weight. That's 8.9 lb/hp-so even after ballasting up, he had to reduce horsepower to meet the 9.5-lb/hp class limit.
Ryan obviously wanted to choke the air at the top end so he wouldn't kill any torque, only the peak horsepower. He tried pinching off the ends of the tailpipes, but this didn't do anything. Then the ignition timing was retarded 6 degrees in 2-degree increments. Unfortunately, removing the first 2 degrees of timing added 10 hp. Ryan took out another 4 degrees, which took out another 10 hp, for a 20hp total reduction. Then the air filter was changed from a 3-inch K&N round to the low-profile 111/42-inch paper element "street rod" filter. This killed another 15 hp, which got him under the limit.
The full Dynojet rear-wheel power figures for the mild carbureted 5.0 are as follows.
Baseline331.1 hp at 5,700 rpm331.7 lb-ft of torque at 4,400 rpm
SupPressed (Timing retarded 6 degrees, low-profile air filter)303.8 hp at 5,800 rpm304.7 lb-ft of torque at 4,400 rpm
Modular engines should not have these issues. Ryan says the 9.5:1 power-to-weight rule was carefully selected to allow the Four-Valve engine all the power it could get with simple bolt-ons (long-tube headers, pulleys, throttle body, and so on) without going into the basic engine. In practice, this means the 5.0 guys have an easy time of making power, while the 4.6 racers have to work harder at it.
Have An American Sedan?What about American Sedan Mustangs currently running in the much larger Sports Car Club of America? Interestingly, even with their much more specific SCCA rule book, American Sedan cars are legal for NASA's American Iron, with two provisions. One, they must run the spec RA-1 Toyo tire, and two, the best SCCA American Sedan cars are probably a tad overpowered to meet the 9.5:1 rule. Simple adjustments ought to take care of both issues.
Alternately, American Sedan cars could enter AIX with no changes, but they would likely suffer a 100hp deficit. Still, for the AS owner looking for another race weekend, AI or AIX offer reasonable alternatives.