5.0 Mustang & Super FordsHow To Engine
Road Race Mustang Engine Build - Iron Lung
Griggs Racing Gives Us An Inside Look At The Engines That Make Its Road-Racing Rockets Breathe
Horse Sense: Not your average racer, and more complex than a two-time-zone Swiss watch with auto-wind, Bruce Griggs is full of surprises. He told us that when he was young, he played percussion and even stood in a couple of nights with the Los Angeles Philharmonic when they were short-handed.
Above all, Bruce Griggs is a racer. While the Mustang world knows him as a suspension specialist-the originator and most successful campaigner of the torque-arm replacement suspension system-Bruce has always been more than that. He's a racer, doing whatever is necessary to get his cars to the front.
That's how the Mustang torque arm came about-Bruce needed it for racing back in the '80s. It's also how numerous other nonsuspension parts Griggs Racing sells landed in its catalog, such as the company's SN-95 front bumper cap with larger foglight and radiator openings, for example. Griggs also offers brake systems using Sierra components, and it has always had quite a few engine offerings. Replacement accessory drives, pulleys, dry-sump systems, whole engines-pushrod or modular-are all available through Griggs.
In fact, it was a NASA American Iron engine that had Bruce calling us to come and take a look. With two American Iron championships to Griggs Racing's credit-in fact, a perfect season last year-why not take a look at the company's latest ideas in American Iron racing engines? Besides offering insight to the racing world, these engines resonate well with performance street needs, so you don't have to trailer your car to learn something from these powerplants.
What makes American Iron engines interesting is the AI power-to-weight rule. Cars are limited by having to carry 9.5 pounds per rear-wheel horsepower. The typical American Iron Mustang, stripped of the easy-to-get-rid-of stuff and carrying the necessary safety gear, weighs between 2,900 and 3,200 pounds. That means 305-336 hp is allowed at the rear tires, which roughly translates into 355-390 hp at the flywheel, depending on a host of variables. That's a nice number for road-racing fun (you can go well over 160 mph on this sort of power) and typical of many street engines.
What's more, the tough on-again, off-again duty cycle of road racing, along with its need for part-throttle driveability and all-around good manners, is also similar to street needs.
Where AI engines spin off on their own is their torque-to-horsepower relationship. American Iron rules may limit horsepower, but they don't say anything about torque. Thus, the holy grail is to build just enough power, but all the torque possible.
With torque at a premium, several facts dominate. Primarily, torque is a function of displacement and cylinder pressure. So, large engines with plenty of squeeze in the combustion chamber make torque. Secondly, while American Iron rules allow carburetors or fuel injection, the long-intake runners of fuel-injection manifolds are more torque-friendly than the stubby-runner stuff of performance-carburetor intakes.