Chevrolet produced two different generations of 427 cubic inch engines that would go down in history as some of the most powerful engines of the time.
Generation 1: W-Series
The first generation of Big-Block engines were the W series, named after its unique valve cover design. The most famous engine in this series was the “so fine” 409. A special 427 cubic inch version of this 409 engine could be ordered under RPO (Regular Production Order) code Z11 for the 1963 Chevrolet Impala Sport Coupe. This special package included an aluminum 427 engine with a longer 3.65 inch stroke, 13.5:1 compression ratio, a high-rise, two-piece aluminum intake manifold and dual Carter AFB carburetors. This combination would produce an under-rated 430 hp and 575 lb·ft torque.
Generation 2: Mark IV Series
Development of the second generation Big-Block engine started with the so-called Mark II Z33 Mystery Motor used in Chevrolet’s 1963 Daytona 500 record-setting stock cars. This “secret” engine was a substantially modified form of the W-series engine, and was released for production in mid-1965 as the Mark IV, referred to in sales literature as the “Turbo-Jet V8”.
Chevrolet Motor Division’s management has always been performance oriented but during the late-50s through the mid-60s upper management at General Motors adopted a “no racing” policy, which meant that Chevrolet’s engineering team had to develop powerplants based on passenger car applications while Ford and Chrysler were experimenting with hemisperical cylinder heads, overhead camshaft setups and multiple four-barrel carburetors. This policy seemed self-defeating but Zora Arkus Duntov led the Corvette group to unleash the most powerful powerplant ever conceived in Detroit. This powerplant was the second design of the L88: a 427 cubic-inch monster that left Chevrolet’s competitors awestruck! Although conservatively rated at 430 hp, the aluminum cylinder head equipped L-88 was easily capable of churning out close to 600 horsepower in a stock configuration.
As an option code on the 1967 to 1969 Corvette and after two years of development, the L88 took the 427 Big-Block step further. Almost every component was reconsidered for power and racing endurance by adding a strengthened crankshaft, 12.5:1 pistons, solid lifter camshaft and a 850 CFM dual feed Holley carburetor. Running on racing fuel, the L88 was capable of 600 horsepower, on the road, and far above GM’s 430 hp figure, the L88 can claim anywhere from 550 to 570 horsepower in production trim.
Out of all the 427 versions, the all aluminum 427 cubic inch ZL1 engine produced in 1969 is the most highly sought after. It was developed ultimately for Can-Am racing and therefore necessary for Chevrolet to produce it as an RPO in order for it to qualify. The engine featured an aluminum cylinder block with iron cylinder sleeves which reduced the engine weight to 575 pounds. The cylinder block was patterned after the cast iron 427 L88, but it wasn’t just a change of the block casting material. The engine was engineered for the capability for a dry sump oil system, an optional gear drive for the camshaft, strengthened bearing journal web areas, external web braces and extra pads inside the lifter valley to allow for additional head bolts.
1969 Chevrolet Mark IV, L88 Engine Specifications
Manufacturing Plant: Tonawanda, New York Cylinder Block: cast iron, 4-bolt main Bore: 4.251 in Stroke: 3.760 in Displacement: 427 cu in Crankshaft: forged Tifftrided 5140 alloy steel Compression Ratio: 12.5:1 Pistons: forged, high-silicon alloy aluminum, 51.7cc dome, floating wrist pins Piston Rings: 1/16 inch compression rings Camshaft: high-lift mechanical camshaft, GM# 3928911 Duration: 354/360 Lift: .540/.560 Lash: .022/.024 Overlap: 133 Seat-To-Seat Timing (TDC Based): 61.0 IVO 113.0 IVC 108.0 EVO 72.0 EVC Cylinder Heads: CanAm-Spec, aluminum, rectangular port, open chamber Valvetrain: 7/16 pushrods, 2.19-inch intake valves, 1.84-inch exhaust valves, 45-degree seat face Induction: aluminum single-plane, open plenum intake manifold, 850 Holley 4 Bbl SAE Gross Power (advertised): 430 hp @ 5200 rpm SAE Net Torque (advertised): 460 lb·ft @ 4000 rpm SAE Gross Power (actual): 550-570 @ 6200-6400 rpm SAE Net Torque (actual): 470 lb·ft @ 5200 rpm