408ci LS2 Engine Build - Blow By

It's really hard to beat factory GM rockers, so Turn Key saw no need to go exotic. These roller rockers are lightweight, affordable, and battle proven.

To ensure that the balancer doesn't spin on the crank snout during blower operations, Turn Key drilled and pinned the assembly. It's extra steps like this that help ensure trouble free throttle mashing later on.

With the long-block done, Turn Key turned its attention to the really fun stuff: bolting on the Kenne Bell twin-screw blower. The first step was getting the blower manifold and intercooler secured in place.

With the intake torqued down, we put the 2.8-liter displacement supercharger in place. To ensure a tight seal, Turn Key applied a bead of black silicone around the port to the intercooler.

Feeding air to the hungry blower is Turn Key's 90mm cable-actuated throttle body. Once in the Nova we will most likely have to switch to a 180-degree turn throttle body intake.

Turn Key also provided an eight-rib drive system. According to Turn Key's Kory Enger, this kit has been modified to hold up to the stresses that a blower can produce. It utilizes a heavy-duty diesel-truck tensioner and mounts like the alternator bracket and been heavily beefed up.

Since blown engines are thirsty under boost, these Aeromotive rails will supply gobs of fuel to the 62-lb injectors. Turn Key's racks holds the GM coil packs in place and their simple-to-install five-wire harness and MEFI4b computer were also put in place.

The beauty of blown engines is that just by swapping a pulley you can go from a street cruiser to a crazy horsepower track car. We decided to go with a 2.75-inch pulley, but Kenne Bell offers a 2.5-inch version as well.

Here she is, all dressed up and ready to head over to Westech Performance for some good old-fashioned dyno flogging. The chromed goodies from Turn Key show that you can be both show and go if you try hard enough.

With the 408 strapped to the Superflow 902 dyno at Westech, we spent the morning dialing in the engine's air/fuel ratios and experimenting with different sized pulleys. The best street combo was a 2.75-inch pulley and 91-octane gas. Once dialed in, we nailed a best pull of 778 horsepower at 6,600 rpm and 710 pounds of twist way down at 3,700 rpm (11 psi of boost). For giggles we bolted on the 2.5-inch pulley and dumped in 114-octane Rocket Brand race gas. Our reward was 803 horsepower at 5,650 rpm and 813 ft-lbs at 3,700 rpm. We had to stop the pull at 5,650 because the injectors were maxed out! After checking the dyno we were hitting over 20-lbs of boost, so we put the 2.75-inch pulley back on and called it a day. After all, this is for a street car.

It's sort of difficult to call this a torque "curve", but that's the beauty of a supercharged engine; loads of torque way down low and it just keeps on going all the way up to the rev limiter. With the tame camshaft we used, the LS engine idles like a dream where it still makes 15 inches of vacuum.