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Mark IV Big Block Chevy Engine - The Mark of Chevy Power

Where Chevy Muscle Really Lives

By Paul Zazarine, Photography by Courtesy of GM

The legend began on the high banks of Daytona in February 1963. A handful of Chevrolets arrived for the Daytona 500 with something "mysterious" under the hood. While Ford and Chrysler expected to compete against Chevrolet's venerable "W" head 409, the Bow-Tie guys had a rather large surprise waiting for them. As Junior Johnson's Chevy thundered around the track at speeds in excess of 160 mph, every soul from the garages, to the pits, to the stands knew that was no W block. Hot on Junior's heels was Johnny Rutherford in another Chevy. The Chevrolets of Ray Fox, Smokey Yunick, and Bubber Farr all ran with power unmatched by the 409, and Ford and Chrysler cried foul. What was this "mystery motor" that Chevrolet was running?

Inside Chevrolet Engineering, it was called the Mark II, a 427ci V-8 that had no bloodline with the 409, which was dubbed the "Mark I." The word "Mark" was derived from the European tradition of using "Mark" to designate succeeding phases of a design. Instead, it was a totally new design that started in the summer of 1962 when Chevrolet Engineering's Dick Keinath started work on a replacement for the W block. Keinath started with the same bore centers (4.84-inch) as the W block. To keep things differentiated in the minds of Chevy engineers working on both engines, the planned successor to the W block was dubbed "Mark II." It was this big-bore, short-stroke 427 powerhouse that tore up the Daytona high banks.

The Mark III was a 1963 design study that had features like the Mark II, but had a bigger bore center. None were produced, since it required too much tooling money at the Tonawanda engine plant to change bore centers. The Mark IV went into production in 1965, displacing 396 ci. Mark IVs were subsequently produced in versions of 427 and 454 cid. Deck heights were 9.80 inches

The cylinder heads were kept under wraps at Daytona in 1963, and all throughout the development process. Less than 50 of these engines had been cast before GM slipped out of racing in January 1963. The large-diameter valves were canted, causing them to stick out at odd angles, which then lead to the engine being nicknamed "Porcupine."

From 1965 until it was discontinued in 1974, the Mark IV big-block was produced in a variety of horsepower configurations. It served duty in everything from mundane station wagons with trailer packages, to pavement-melting super Chevys that ruled the streets and the drags.

Even after they were discontinued from production, the Chevy big-block continued on as the GEN II crate motor that powers drag cars, street rods, and the hottest street machines today. Like all great engines, the Chevy big-block will be around to power street machines for generations to come.

The Mark IV 396ci V-8 was introduced in 1965, and was available in the Corvette and the full-sized Chevrolet. With the valve cover removed, the staggered arrangement of the valves is clearly visible. Header-like exhaust manifolds were extremely efficient.

The '67 L34 396ci V-8 was optional on the Chevelle and Camaro. It was rated at 350 hp. Performance versions of the 396 used an open-element air cleaner.

The '66 L72 427 was offered in both the big Chevrolet and the Corvette. The L72 produced 425 hp, and utilized big 2.190-inch intake and 1.720-inch exhausts. The '66 L35 used smaller 2.065-inch intake valves and produced 390 hp.

One of the most famous big-blocks is the '67 L71. This 427 was rated at 425 hp, and a thumpin' 460 lb-ft of torque. A trio of Holley two-barrel carburetors drew air through a triangular-shaped air cleaner with a low-restriction polyurethane element.

The King Kong of the Mark IV family was the '67-'69 L88. It differed very little from the '69 all-aluminum ZL1 shown here. The major difference was that the L88 used an iron block. Both engines were ridiculously underrated at 430 hp, and were true race engines. Chevrolet sold just 216 L88-equipped Corvettes between 1967 and 1969. Only two ZL1s were installed at the factory in '69 Corvettes. A total of 69 ZL1s were installed in '69 Camaros under special Central Office orders. The ZL1 had a 12:1 compression ratio and used an alloy aluminum block with dry cylinder sleeves. Aside from that major difference, it and the L88 were virtually the same. Both used mechanical lifters and 1.70:1 rockers. The ZL1 and the L88 both used 2.185-inch intake and 1.875-inch exhaust valves made of alloy steel. The intake valve face and head was aluminized, while only the exhaust valve's face was aluminized. The L88 had 0.5500 lash at zero lift while the ZL1 had 0.5800 lift at zero lash.

In 1970, the Mark IV was treated to a 0.24-inch bore job, taking it out to 4.00. With the 4.25 stroke unchanged, the new engine displaced 454 ci. The LS5 version produced 390 hp with a hydraulic valvetrain. It was also stymied by emission control equipment.

This is the engine that never was, at least in production form. It's the LS7, and it was destined for the '70 Corvette. None were ever installed at the St. Louis assembly plant. The 460hp LS7 in this factory photo shows a trio of Holley two-barrel carburetors. Factory specifications, however, indicate that a Holley four-barrel was planned, along with aluminum heads, 11.25:1 compression, a mechanical valvetrain, and a transistorized ignition.

The ZZ502/502 is one of GM's most popular crate engines. It features a complete roller-rocker valvetrain, big-valve aluminum heads, and a dyno-tuned induction and ignition system. It's lightweight, and can be ordered as a long-block or a complete engine kit.

The "King of the Crate Engines" is the new ZZ572/620 that's built around an all-new Gen VI tall deck Bow-Tie big-block. This all-new engine is filled with a forged 4340 steel crank with 4.375-inch stroke, shot-peened, forged 4340 H-beam rods, and forged-aluminum pistons with full-floating wristpins. The 572 makes 620 hp at 5,500 rpm, and 650 lb-ft of torque at 4,500 rpm.

1965-1974 Chevrolet Mark IV Engine Specifications

RPO Displacement Horsepower Torque Application
1965
L35 396 325@4,800 410@3,200 Chevrolet
L78 396 425@6,400 415@4,000 Chevrolet
L78 396 425@6,400 415@4,000 Corvette
L37 396 375@5,600 415@3,600 RPO Z16 Chevelle
only
1966
L35 396 325@4,800 410@4,800 Chevrolet/Chevelle
L34 396 360@5,200 415@3,400 Chevelle
L78 396 375@5,600 415@3,600 Chevelle
L36 427 390@5,200 470@3,600 Chevrolet/Corvette
L72 427 425@5,600 460@3,600 Chevrolet/Corvette
1967
L35 396 325@4,800 410@3,200 Chevrolet/Chevelle
L34 396 350@5,200 415@3,400 Chevelle/Camaro
L78 396 375@5,600 415@3,600 Chevelle/Camaro
L36 427 390@5,200 460@3,600 Chevrolet/Corvette
L68 427 3x2 400@5,400 460@3,600 Corvette
L72 427 425@5,600 460@4,000 Chevrolet
L71 427 3x2 435@5,800 460@4,000 Corvette
L88 427 430@4,600 485@4,000 Corvette
L89 427* 435@5,800 460@4,000 Corvette
* Aluminum Head
1968
L35 396 325@4,800 410@3,200 Camaro/
Chevrolet/Chevelle
L34 396 350@5,200 415@3,400 Nova/Camaro/
Chevelle
L78 396 375@5,600 415@3,600 Camaro/Chevelle
L89 396 * 375@5,600 415@3,600 Camaro/Nova
L72 427 425@6,400 460@4,000 Chevrolet
L36 427 390@5,400 460@3,600 Corvette
L68 427 400@5,400 460@3,600 Corvette
L71 427 3x2 435@5,800 460@4,000 Corvette
L88 427 430@4,600 485@4,000 Corvette
L89 427* 435@5,800 460@4,000 Corvette
* Aluminum Head
1969
L35 396 325@4,000 410@3,200 Camaro/Chevelle
L34 396 350@5,200 415@3,400 Chevelle/Camaro/Nova
L78 396 375@5,600 415@3,600 Chevelle/Camaro/Nova
L89 396+ 375@5,600 415@3,600 Chevelle/Camaro
L36 427 390@5,400 460@3,600 Chevrolet/Corvette
L72 427 425@5,600 460@4,000 Chevrolet/Corvette
LS1 427 400@5,400 460@3,600 Chevrolet
L72 427 425@5,600 460@4,000 Chevelle *
L68 427 400@5,400 460@3,600 Corvette
L71 427 3x2 435@5,800 460@4,000 Corvette
L88 427 430@5,200 450@4,400 Corvette
L89 427+ 435@5,800 460@4,000 Corvette
RPO Displacement Horsepower Torque Application
ZL1 427@ 425@5,600 460@4,000 Camaro #
ZL1 427@ 430@5,200 450@4,400 Corvette
* COPO 9562,9566,9694
430@5,200
450@4,400
# COPO 9561 427 ZL1
# COPO 9560 427 ZL1
+ Aluminum Head
@ All Aluminum
1970
L34 396/402 350@5,200 415@3,400 Camaro/Chevelle/
Nova
L78 396/402 375@5,600 415@3,600 Camaro/Chevelle/ Nova
LS3 400 330@4,800 410@3,200 Chevelle
LS5 454 390@4,800 500@3,400 Corvette
LS6 454 450@5,600 500@3,600 Camaro
L89 402* 375@5,600 415@3,600 Chevelle
LS5 454 360@5,400 500@3,200 Chevelle
LS6 454 450@5,600 500@3,200 Chevelle
LS7 454 460@5,600 490@3,600 Corvette
* Aluminum Head
1971
LS3 402 300@4,800 400@3200 Chevrolet/Chevelle/
Monte Carlo/Camaro
LS5 454 365@4,800 465@3,200 Chevrolet/Chevelle/
Monte Carlo/Corvette
LS6 454 425@5,600 475@4,000 Chevelle/Monte
Carlo/Corvette
1972*
LS3 402 240@4,400 345@3,200 Monte Carlo/
Chevelle/Camaro
LS5 454 270@4,000 390@3,200 Chevelle/Chevrolet/
Monte Carlo/Corvette
* SAE Net
1973*
LS4 454 275@4,400 395@2,800 Chevelle/Monte
Carlo/Corvette
* SAE Net
1974*
LS4 454 235@4,000 360@2,800 Chevrolet/Monte
Carlo/Chevelle
LS4 454 270@4,400 380@2,800 Corvette
* SAE Net
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By Paul Zazarine
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