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Hemmings Motor News Blog

Hemmings Motor News has been around since 1954. We're proud of our heritage, but we're also more than the Hemmings full of classifieds that your father subscribed to. Aside from new editorial content every month in Hemmings, we have three monthly magazines: Hemmings Muscle Machines, Hemmings Classic Car and Hemmings Sports and Exotic Car.

While our editors traverse the country to find the best content for those magazines, we find other oddities related to the old-car hobby that we really had no place for - until now. With this blog, we're giving you a behind-the-scenes look at what we see and what we do during the course of putting out some of the finest automotive magazines you'll ever read.

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The Chevrolet Mark IV L-88 427 Big-Block Powered Corvettes to Victory

Posted June 23, 2022 5:00 AM by dstrohl
Pathfinder Tags: chevrolet corvette

Chevrolet’s Mark IV V-8 was descended from Chevrolet's NASCAR “mystery motor” program, but there’s nothing mysterious about how these engines made horsepower. One of the most formidable Mark IV V-8s was the 1967-’69 L-88, offered as an under-publicized, underrated Corvette option from 1967-’69 and over the counter at Chevrolet parts departments. The L-88 served as a back channel, for Zora Arkus Duntov and his team, to get 427 Cobra-rivaling horsepower in the hands of Corvette racers, while technically not violating the Automobile Manufacturers Association ban on direct-factory involvement in motorsports.

The L-88 427 made its power (rated at 430 hp but capable of more than 500) the old-fashioned way: cubic inches, high compression, an aggressive cam and a free-breathing top end. There were some significant changes in ’69, but the engine’s basic recipe remained the same: an iron block with four-bolt mains capping off a cross-drilled, forged-steel crankshaft; forged-steel connecting rods with floating wrist pins (rather than pressed in) topped with forged pistons; an aggressive mechanical camshaft; aluminum heads with 2.19/1.88-inch valves; and a high-rise aluminum intake fed by a single Holley four barrel.

The ’67-’68 engines used closed-chamber heads, had 12.5:1 compression, and connecting rods with 3/8-inch bolts. In ’69, the L-88 was equipped with better-breathing open-chamber heads (that also lowered the compression ratio slightly), reshaped pistons, rods with 7/16-inch bolts, and a crankshaft to accommodate the new rods.

Actual L-88 Corvette production is a topic of debate, but the generally agreed upon total is 216: 20 in ’67, 80 in ’68, and 116 in ’69. Because the L-88 engine was available through dealers, many more have found their way into Corvettes as well as other Chevrolet cars and some speed boats.

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