Katech is certainly on the front row of the race to build the most powerful naturally aspirated LT1 street engine with the release of its 700-horsepower Street Attack C7 427.
The video above demonstrates the level of testing the company goes to validating the engine, which has been in development for some two and half years. Running a program that simulates laps over the Daytona road course, the test engine was subjected to three hours of up and down shift patterns and straightaway top speeds.
“We just kept making changes and testing, getting everything just perfect and refined for a street engine,” says Jason Harding, director of aftermarket operations at Katech.
The finished product is rated at 700 horsepower with 620 lb-ft peak torque. Redline is 7,000 rpm. It’s available either as a crate engine, or the customer can bring in a late-model Corvette or Camaro and Katech will modify the engine.
Making that much power from an engine rated at 460 horsepower at 6,000 rpm in factory crate form required more than just playing with the cam, heads and intake. It meant poking the cylinders out from 4.065 to 4.125 and replacing the stock 3.622-inch stroke crank with a longer 4-inch arm. If those numbers sound familiar, it’s because those are the specs for the 7.0-liter LS7.
“We wanted to see how big we could make it,” says Harding. “We started with a 4.070 by 4.100 before going same as the LS7.”
Katech machines the block in house before inserting new liners that can be bored out to 4.125. The new rotating assembly comprises a Callies forged 4340 crankshaft, Callies forged H-beam rods and Diamond 2618-alloy pistons that bump the compression ratio up from 11.5:1 to 12.5:1.
“We use the same piston-dome geometry from the factory because of the direct injection,” explains Harding. “It still runs on premium pump gas.”
Katech modified the stock injectors to flow more. Adding more air to the fuel is a MSD Atomic Air Force intake manifold and a Katech 103mm billet throttle body. Katech also CNC-ported the LT1 cylinder heads.
“The port design is all new because the head is so different,” says Harding.
A more aggressive camshaft is turned by a timing set originally designed for the Corvette C5.R race team. Katech restricts the amount of cam phasing with a mechanical limiter to avoid any valve contact inside the cylinder. The hotter cam also requires high-speed lifters and high-lift valve springs. Since the old AFM lifters are no longer used, Katech installs a new valley cover that blocks off the unnecessary oil passages and eliminates the oil manifold for the lifters. Other upgrades include ATI damper, redesigned piston squirters that clear the crankshaft, titanium valve-sprint retainers and proprietary dry-sump oil pan, tank and secondary scavenge pump from ARE. The Street Attack package is also available in wet-sump.
Finally, the engine management system is recalibrated and the engine is dyno tested. Katech will announce pricing shortly.