compression, hydraulic lifters, nodular iron crankshaft, and two-bolt main caps. It produced (1970), (1971), (1972 net horsepower, single or dual exhaust). L-34: produced 1970. Same as L-34 from 1967 to 1969. L-78: produced 1970. Same as L-78 from 1966 to 1969. 427 The highly successful and versatile version of the Mark IV engine was introduced in 1966 as a production engine option for full-sized Chevrolets and Corvettes. The bore was increased to , with power ratings varying widely depending on the application. There were smooth running versions with hydraulic lifters suitable for powering the family station wagon, as well as rough-idling, high-revving solid lifter models usually applied to a minimally equipped, plain-looking, two-door Biscayne sedan fitted with the version of the 427 - (RPO L72). Perhaps the ultimate 427 for street applications was the at 5800 rpm and at 4000 rpm of torque L71 version available in 1967 to 1969 Corvettes, and in the Italian Iso Grifo. This engine was identical to the L72 427 (first introduced in 1966), but was fitted with 3X2-barrel Holley carburetors, known as "Tri-Power", in lieu of the L72's single 4-barrel carburetor. Both engines used the same high-lift, long-duration, high-overlap camshaft and large-port, cast-iron heads to maximize cylinder head airflow (and, hence, engine power) at elevated engine-operating speeds. Consequently, the engines offered very similar performance and resulted in a car whose performance was described by one automotive journalist as "the ultimate in sheer neck-snapping overkill". Typical magazine road tests of the day yielded 0- in 5.6 seconds and in 13.8 second at range for both the L72 and L71. In 2011, Super Chevy Magazine conducted a chassis dynamometer test of a well documented, production-line, stock but well-tuned L-72 "COPO" Camaro, and recorded a peak at the rear wheels, demonstrating the substantial difference between 1960s-era SAE "gross" horsepower ratings and horsepower at the wheels on a chassis dynomometer. Wheel horsepower (which is obtained at the drive wheels and thus takes into account drivetrain power loss) does not equate to SAE net HP (which is horsepower at the flywheel, like SAE gross, but with all accessories included, unlike SAE gross). The RPO L89 was an L71 fitted with aluminum heads. While this option produced no power advantage, it did reduce engine (and hence, vehicle) weight by roughly . This resulted in superior vehicle weight distribution for improved handling, although the difference in straight line performance was negligible.