Building an engine to deliver a required power level at a specific rpm presents its own set of challenges to the builder.

“Yeah, it went through a number of phases before it was perfected,” says Lee Carson of United Racing Engines in Phoenix.

The order came from a New Zealand client who was sourcing engines for an Asian airboat manufacturer. The engines needed to pull around 450 horsepower with a comparable torque output at 5,100 rpm.

“The engines were not to go over 5,200 rpm, which is where the blades become less effective,” says Carson. “It doesn’t matter if it makes 1,000 horsepower. If it’s past 5,200 rpm it’s useless.”

Another requirement was establishing a low compression ratio as the best fuel available in the area is just 87 octane.

“We kept it in the 8.9 range to keep the engine safe,” says Carson, adding that ignition timing was also conservative at 34 degrees.

The foundation is rather typical of strong street engine: GM 1-piece rear seal block, Scat crank and rods and KB pistons.

“We went through some head changes and found the best combo to be the AFR 195 with special hydraulic roller cam ground for that rpm range,” explains Carson.

On top is an Edelbrock Performer Air-Gap intake and a Quick Fuel 850 CFM 4-barrel with mechanical secondaries. Due to the nature of the engine’s intended environment, numerous sensors were installed to monitor all critical functions. Also, a resin-filled coil is utilized to withstand the heavy vibrations.

The engine was dyno’d at URE and independently at Westech Performance where steady state tests were conducted to confirm power levels at 5,100 rpm.

Ironically, it was a big-block project that served as the foundation for this engine’s strategy. That engine was designed to deliver peak power at 5,400 rpm.

“We started with that cam design and concept,” says Carson, “and then carried it over to the small-block.”