Chevrolet had introduced its popular small-block V8 in 1955, but needed something larger to power its medium duty trucks and the heavier cars that were on the drawing board.

As with the 265 and 283 cu in (4.3 and 4.6 L) "small-block" engines, the W-series valve gear consisted of tubular steel pushrods operating stud-mounted, stamped-steel rocker arms.

Due to the relatively low mass of the valve train, mechanical lifter versions of the W-series engine were capable of operating at speeds well beyond 6000 rpm.

This arrangement was achieved by combining a cylinder head deck that was not perpendicular to the bore with a crowned piston, which was a novel concept in American production engines of the day.

As the piston approached top dead center, the angle of the crown combined with that of the head deck to form a wedge-shaped combustion chamber with a pronounced quench area.

"[14] The first iteration of the W-series engine was the 1958 "Turbo-Thrust" 348-cubic-inch (5.7 L), originally intended for use in Chevrolet trucks but also introduced in the larger, heavier 1958 passenger car line.

In addition, a 340 hp (254 kW) version of the 409 engine was available from 1963 to 1965, with a single 4-barrel cast iron intake mounting a Rochester 4GC square-bore carburetor, and a hydraulic-lifter camshaft.

[17] This was a special package created for drag racers, as well as NASCAR,[18] and it consisted of a cowl-induction 427 cu in (7.0 L) engine and body with selected aluminum stampings.

A high-rise, two-piece aluminum intake manifold and dual Carter AFB carburetors fed a 13.5:1 compression ratio to produce an under-rated SAE gross 430 hp (321 kW) and 575 lb⋅ft (780 N⋅m).

This "secret" engine was a unique design incorporating aspects of both the W-series and the mid-1965 introduced Mark IV,[20] referred to in sales literature as the "Turbo-Jet V8".

The valves continued to use the displaced arrangement of the W-series engine, but were also inclined so that they would open away from the combustion chamber and cylinder walls, a design feature made possible by Chevrolet's stud mounted rocker arms.

This alteration in valve placement resulted in a significant improvement in volumetric efficiency at high RPM and a substantial increase in power output at racing speeds.

[26] As part of the head redesign, the spark plugs were relocated so that they entered the combustion chamber at an angle relative to the cylinder centerline, rather than the straight-in relationship of the W-series engine.

Like its predecessor, the Mark IV used crowned pistons, which were castings for conventional models and impact extruded (forged), solid skirt types in high performance applications.

The all-aluminum 1969 ZL1 version of the 427 engine was developed primarily for Can-Am racing,[citation needed] which did not require homologation to compete,; it was very successful in cars like the McLaren M8B.

As impressive as the ZL1 was in its day, actual engine dyno tests of a certified production line stock ZL1 revealed 376 hp (280 kW) SAE net with rated output swelling to 524 hp (391 kW) SAE gross with the help of optimal carb and ignition tuning, open long tube racing headers, and with no power-sapping engine accessories or air cleaner in place.

High-Performance Cars tested a production line stock, but well tuned, example and recorded a 13.1 second/110 mph (180 km/h) 1⁄4 mile (402 m), which correlates quite well with the previously referenced 376 hp (280 kW) SAE Net figure.

Using Patrick Hale's Power/Speed formula, the 122.15 mph (196.58 km/h) trap speed indicated low 11-second ET (elapsed time) potential (e.g. with larger drag slicks) and suggested something on the order of 495 hp (369 kW), "as installed", in that modified configuration.

However, most of these items were racing parts originally designed for Can-Am competition that found their way onto dealers' shelves, and were meant to boost the engine's power output.

Beginning in 1969, the highest performance 427 models were fitted with the new open (vs. closed) chamber cylinder heads, along with design improvements in crankshafts, connecting rods, and pistons, adopted from the Can-Am development program.

[38][39] The AHRA ASA (Showroom Stock Automatic) Class record-holding Chevelle LS-6 for the 1970 racing season posted a best-of-season trap speed of 106.76 mph (172 km/h),[40] which suggests something on the order of 350 "as installed" (SAE Net) HP for a 3,900 pounds (1,769 kg) car-and-driver combination.

In 1972, only the LS-5 remained, when SAE net power ratings and the move towards emission compliance resulted in a temporary output decline, due to lowered compression, to about 270 hp (201 kW) and 468 lb⋅ft (635 N⋅m).

Hardened valve seats further increased reliability and helped allow these engines to last much longer than the earlier versions, even without the protection previously provided by leaded fuel.

Mark IV engines saw extensive application in Chevrolet and GMC medium duty trucks, as well as in Blue Bird Corporation's All American and TC/2000 transit buses (the latter up until 1995, using a 427 with purpose-built carburetor).

Both the 366 and 427 commercial versions were built with a raised-deck, four-bolt main bearing cap cylinder to accommodate an extra oil control ring on the pistons.

GM offered it in their Performance Parts catalog, available as multiple crate motors with horsepower ratings from 338 to 600 hp (252 to 447 kW) and torque of 470 to 567 lb⋅ft (637 to 769 N⋅m) in "Base" and "Deluxe" packages.

[43] The "Ram Jet 502,"[44] the 496 hp (370 kW) / 565 lb⋅ft (766 N⋅m) crate motor, was offered with fuel injection, and came as a turn key setup which included all the wiring and electronics needed to operate in any vehicle.

The ZZ632's iron block shares a mold with Chevrolet Performance's ZZ572 crate engines, but the castings are machined to accommodate the huge 632 cubic-inch displacement.

[63] GM sold the Vortec 8100 to Workhorse (now a division of Navistar), making it one of the most popular engine choices in gasoline-powered Class A motorhomes during the early 2000s.

– are available in stock or modified configurations, as well as with increased deck height to allow for a longer stroke or more favorable rod length ratios, depending on intent, providing the ability to make engines with capacities of 632-cubic-inch (10.4 L),[65] 798-cubic-inch (13.1 L),[66] and as large as 1,005.8-cubic-inch (16.5 L).