Street/race engine development is starting to outpace the capability of most engine dynos. Case in point: Nelson Racing Engines was twisting its dyno with a 572ci big-block Chevy when steam started pouring out of the water brake around 6,000 rpm. Even though the power curve was still on a northward climb, the team was left with little choice but to guess as to the power output.
“Personally, I think it could have made 2,800 horsepower,” NRE boss Tom Nelson tells EngineLabs. “But we called it 2,500 just because everyone will cry about it.”
The Rat motor is built around a Dart tall-deck block, Callies Magnum crankshaft, Oliver billet rods and custom-made JE pistons. There’s also a custom-ground cam that motivates Comp Cams Elite Race roller lifters, Smith Bros. pushrods and T&D rocker shaft-mounted rocker arms. On the bottom side is a Aviad dry-sump system and custom oil pan so the big-block can fit into a Dodge Viper chassis. The heads are Brodix 24-degree, rectangular-port CNC heads topped with NRE billet valve covers.
“We alway change the valve jobs for the turbo motors,” adds Nelson. “Plus, we add Inconel valves.”
The induction is all NRE trademark components, like the twin 88mm mirror-image turbos, stainless-steel headers, air-to-water intercooler and unique Alien intake manifold.
“The Alien has the fuel regulator and fuel rail all built in. You don’t have to mount anything” explains Nelson, adding that the manifold also houses the throttle-position, MAP, coolant and air-temperature sensors. “Even the boost references are internally drilled and o-ringed.”
The Alien is also fitted with two fuel injectors per cylinder: the primary is 83 pounds while the secondary is rated at 154 pounds. The primary and secondary injectors operate from separate fuel lines.
“The secondary comes on only when you get into boost,” says Nelson. “So, you could run 91 octane on the primary side, then feed race gas to the secondary injectors. Or it could be all race gas or all pump, depending on what boost level you want to run. We call it NRE Octane On Demand. If you want to drive it on the street, you don’t have to kill yourself in the wallet.”
Also helping to promote a clean look are the wires neatly bundled into a single Deutsch connector and a hidden throttle linkage.
“From a racer’s standpoint, it kinda sucks,” admits Nelson, “because it’s hard to get to everything. But from a beauty standpoint, everything is hidden. Doesn’t even look like the motor runs.”
The video shows a preliminary run on 12 pounds of boost up 6,500 rpm where the engine pulled 1,608 horsepower and 1,300 lb-ft torque. Stepping up to 18 pounds, the dyno recorded 1,940 horsepower with 1,670 lb-ft, at 6,100 rpm, and numbers were climbing hard. Another run with nearly 25 pounds saw an early shutoff but more than 1,800 lb-ft of torque and 2,100-plus horsepower.
“It’s on the edge of streetable,” sums up Nelson. “There was so much left in that motor but the dyno was giving up. We’ve had that motor at 38 pounds, so it’s a bad boy!”