While usually showcasing twin-turbocharged engines that tear up dynos or belch fire on its video channel, Nelson Racing Engines is now featuring a street-worthy 474ci LS engine that makes over 700 horsepower and boasts a thundering torque band–all accomplished with a naturally aspirated induction.
NRE achieves the large displacement by starting with a RHS tall-deck aluminum block bored to 4.155-inch and fitted with a Callies 4.375-inch-stroke crankshaft. Rest of the rotating assembly includes Callies rods and JE pistons that squeeze out a pump-gas-safe 9.8:1 compression ratio.
“Actually, this is a good revving motor [even with undersquare bore-stroke ratio],” adds Nelson. “We could turn it to 7,000.”
The engine boasts a factory dry-sump system but with an ATS pan from Speedtech Performance designed to fit in a ’69 Camaro. The All Pro heads are ported at West Coast Racing and fitted with Jesel rockers. NRE custom designs the hydraulic roller cam to match the heads.
“With turbos there’s force-fed air, so you down’t want a lot of that fresh air going out the exhaust with a cam that has too much overlap,” explains Nelson. “On a naturally aspirated motor you can have more overlap, as long as you make sure the heads flow really good. And you also get that bitchin’ sound.”
In typical NRE fashion, the engine takes on a rather menacing character with an all-black color scheme and the imposing and all-billet Alien/Anteater induction sitting on top. Unlike the twin-turbo intakes from NRE that have two injectors per cylinder–the extra one used for octane enrichment under full boost–this Alien intake has single injectors. The smooth design of the intake manifold hides the injectors, fuel rails, sensors and regulators. And the Anteater air tube will hide the twin throttle bodies and pedal linkage.
On the dyno the engine pulled peak torque of 612 lb-ft at 5,200 rpm, but there was more than 500 lb-ft starting at 3,800 rpm up through the end of the run. Nelson says the video run was hampered slightly by rainy atmospheric conditions, resulting in 686 horsepower at 6,400 rpm.
“On a good day it made 708,” he says.