Harken back to the heyday of the musclecar revolution and imagine using hindsight to sit across the desk at your favorite Chevrolet dealer to order up a 1967 Corvette with the legendary RPO code L88. For a scant $947.90, you could have checked the option for the aluminum headed 427 that was conservatively rated at 430 gross hp (at 5,200 rpm) and 460 ft-lbs of torque (at 4,000 rpm). The Chevrolet big-block featured a 4.251-inch bore, 3.76-inch stroke and 12:5:1 compression. With a mechanical lifter camshaft that featured 264 degrees of intake and 269 degrees of exhaust duration (measured at .050-inch lift) with .560-inch intake and .580-inch exhaust lift, it was designed to be revved to 6,400 rpm, where it would wake up and reach its power potential. This was a solid lifter race motor, never meant for daily driving. GM tried to keep the actual horsepower of approximately 500 a secret, and to a degree was successful with only a mere 216 Vettes factory equipped with the L88 from 1967-69.
Fast forward to 2006 and you can walk into your Chevrolet dealer and check off option code 1LZ or 2LZ and order yourself a new Z06 Corvette featuring the 7.0 liter (427 cubic inch) LS7 engine. The upgrade to a Z06 carries with it a $21,200 price tag, but includes much more than the LS7 engine and its crate motor retail price of $13,895 (under PN 17802397). Carrying a conservative net horsepower rating of 505 (at 6,300 rpm) and 470 lb-ft (at 4,800 rpm), the all-aluminum engine is the ultimate factory Gen IV small-block and a direct descendant of the impressive C5R racing efforts. The rigid aluminum block carries 6-bolt main caps, a 4.125-inch bore by 4.00-inch stroke, and an 11:0:1 compression rating. The hydraulic roller cam specs out at 230/231 at .050 with .591-inch lift on 1.8 roller rockers and is designed to be revved up to 7,000 rpm.
LS7 owners looking for increased power are doing exactly what the original L88 owners did; replacing the cam, exhaust manifolds and exhaust system with the best that the aftermarket has to offer. Horsepower of 550-575 was obtainable with the L88, but along with the power came a radical idle and poor street manners. Since the LS7 idles as well as any modern car of its generation, what would happen if you swapped out the cam for a more aggressive design and freed up the exhaust? Enter Horsepower Engineering (HPE) of Houston, Texas. Founded in 2001 by owner Chuck Anders, the 13,000 square-foot facility has been pushing the envelope on late model GM performance. As the shop that lays claim to the fastest LT1 F-body, along with the fastest stock block LS1 in the country, big power and HPE go together.
According to Chuck Anders, "the LS7 is a fantastic engine with excellent street manners. Substantial power gains can be achieved by optimizing the camshaft and the exhaust system. Our C6ZS2 (Stage II) camshaft package was custom designed for the owner desiring stock like drivability, moderate lope at idle and noticeable power gains. Although the Z06 features hydro-formed tubular steel exhaust manifolds and a 3-inch exhaust system, the LS7 heads are quite restrictive on the exhaust side. Anything you can do to increase the flow of the exhaust helps power on the LS7." By utilizing a set of the new D-port Kooks 1 7/8-inch headers and 3-inch mid-pipe with high-flow metal substrate cats, increased exhaust duration is allowable due to the excellent scavenging of the Kooks components. Throw in a ported HPE throttle body and a Halltech PowerCore air filter and the engine wakes up very nicely.
Follow along as HPE searches for big power on an LS7 by installing a custom ground camshaft, Kooks headers, Kooks mid-pipe with high-flow cats and a Halltech PowerCore high flow LS7 air cleaner on a 2006 C6 Z06, owned by Sanjay Mehta, a radiation oncologist from Houston, Texas. With a mere 3,500 miles on the odometer, his stock-configured Z06 belted out 465 rear-wheel horsepower. Shop manager and lead technician Josh Ledford of HPE will handle installation of the components while HPE owner Chuck Anders will dive into the powertrain control module and retune the car to maximize the power potential. After wrenching and replacing the parts, we'll show you how much power was added to a bone stock Z06. Will the LS7 respond to the changes much as the L88 did and put out close to 575 horsepower?
HPE's Z Series Camshaft and Power Packages
The HPE C6Z series of camshaft packages retails for $999.95 and consists of cam, dual valvesprings, titanium retainers, Super 7 locks, locators, seals, custom length pushrods, and new crankshaft balancer bolt. The custom-ground COMP Cams are offered in Stage I, II and III varieties. The Stage II cam specs as used in our test car, come out at 230/242 at .050 on a 114 LSA with a .607/.620 lift on 1.8 rockers. The Stage III cam specs are under lock and key somewhere in the Dominican Republic and would require 32 members of the Mafia and one very loud 300-pound opera singer to get them past Chuck's lips.
COMP also supplies the custom length Hi-Tech 3/8-inch pushrods. The pushrods are a one-piece design constructed of 4130 seamless chromoly with an outstanding wall thickness of .080 in. The pushrods are heat treated to a "60" hardness on the Rockwell "C" scale and finished in a black oxide.
Patriot Performance "Gold" dual valvesprings (PN 8401) are capable of up to .650 lift and include titanium re-tainers, machined bases, Super 7 locks and Viton rubber intake and exhaust seals. The Patriot Gold springs feature an open spring pressure of 380 pounds, with 135 pounds closing pressure as compared to approximately 310 and 110 pounds for the factory springs.
In addition to the camshaft packages, HPE offers the following components to make up a Power Package. Key to the power packages is intake and exhaust changes designed to maximize flow.