Cast from 355 T6 alloy, the intake fits a new 7.0-liter, LS7-based COPO engine package that includes the LSX-DR cylinder heads from Chevrolet Performance. The upgraded 450-horsepower showdown engine package was recently approved by NHRA and includes a number of technical specification changes over the standard 427ci 430-horsepower rating established by the sanctioning body. That engine has been offered in the 2012-2014 COPO Camaro, but the new engine is approved only for the 2014 COPO Camaro.
“This engine package addresses the new 426 Hemi Drag Pak that NHRA approved for the Dodge Challenger,” Chevrolet Performance’s Roger Allen tells EngineLabs. “So we developed a 427 that uses our LSX-DR heads that go with this new manifold. It was just approved for competition, and racers are now building the engine.”
The Super Stock Showdown is designed to showcase high-performance products from Detroit, including the Ford Mustang Cobra Jet, Dodge Challenger Drag Pak and Chevy COPO Camaro. The race is run at four NHRA events each year, with the first already staged at the Gatornationals in March. Upcoming events include the Indianapolis, Maple Grove and Las Vegas. Competition includes entries from both the FS/A and FS/B classes. The winners of two classes, which are raced within the regular Stock class competition, then square off with a three-tenths staggered start (FS/A is for supercharged vehicles). Last year, almost 30 cars competed at the US Nationals.
Besides the new heads and intake, other changes over the original 427 COPO engine include a switch from hydraulic roller to solid roller camshaft and stepping up to 1.9:1 rocker arms from 1.8:1 models. The DR head (casting # 19172381) also uses dual coil springs, compared to the beehive on the original 427, and the valves are bigger: 2.280/1.620 vs. 2.205/1.615. Allowable compression ratio is also higher, 14.9:1 over 14.58:1. Both engines are based on the factory LS7 block and feature a 4.125 x 4.000 bore/stroke with 6.100-inch connecting rods.
The new intake manifold, which carries GM part number LSXDR427, was designed in conjunction with Chevrolet Performance and CFE. A sheet-metal prototype was built following extensive computer modeling and CAD work between the two groups, then tested at Cagnazzi Racing.
“Once we came up with a configuration that met the performance targets, CFE then developed the casting,” says Allen.
The original COPO manifold is a “ram-jet” style design with a front-mounted throttle body. The CFE design positions the throttle body over the plenum.
“Running a more conventional Dominator-style throttle body seemed to help with the air-fuel distribution and allow the motor to make more power up high,” reports Scott Kieffer of CFE Racing.
The intake is cast from 355 T6 alloy and features O-ring sealing between the plenum and top plate. Precise CNC machining ensures equal runner lengths and consistent radius at the runner entrance. It’s designed for a standard 9.240-inch deck height and comes with fuel-injector mounting provisions as well as a dedicated fuel rail with -8 AN fittings.
“This manifold was developed to meet the rules criteria,” says Kieffer. “But it can also be used in other non-restricted applications.”
The approved manifold requires an Accufab 4B4500-2 throttle body, which is based on a Dominator/4500-style footprint and comes with 2-inch throttle blades. However, CFE can provide a different top plate to support dual throttle bodies, and nitrous port injection could also be plumbed into the runners.
The manifold is available at CFE Racing or through Chevy Performance dealers, and Allen says teams are already working with the new package for their 2014 Camaros.
“We hope to see at couple of them at Indy for the US Nationals,” adds Allen.