Examining The Legendary Chevrolet Big-Block Engine

L88: The First Aluminum-Headed Big-Block

This is an early L88 (1966)... 

   

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This is an early L88 (1966) test engine on a pallet.

Talk about breaking new ground, the L88 did so literally andfiguratively. Although it shared the same dimensions (4.251-inch bore,3.76-inch stroke) as its other 427 stablemates, the L88 has becomelegendary for its combination of stump-pulling torque and high-flyinghorsepower. The engine wasn't given a horsepower rating when it wasintroduced in mid-year 1967, but, ultimately, engineers at Chevroletplanted their tongues firmly in their collective cheeks and proclaimedits output at 430 hp at 5,200 rpm. The issue wasn't that the rating wasfalse, it was merely skewed. L88s undoubtedly produced something on theorder of 430 hp at 5,200 rpm. But left unsaid was that it also producedapproximately 500 hp at 6,400 rpm (the engine speed at which most othersolid-lifter-equipped big-blocks were rated). It's also been claimedthat when equipped with headers and an open exhaust, actual output wasin the vicinity of 550-575 hp.

The L88 was set apart from other 427 engines by its large-port aluminumcylinder heads and 12.5:1 compression ratio. Other special equipmentincluded a specially modified aluminum intake manifold, an 850-cfmHolley four-barrel, a mechanical lifter cam with 264 degrees of intakeand 269 degrees of exhaust duration (measured at .050-inch lift),.560-inch intake and .580-inch exhaust lift, special valvesprings, a2.19-inch intake, 1.84-inch exhaust valves, and 7/16-inch-diameterpushrods.

The L88 was a race engine. Period. However, race engines typically findtheir way into street-driven cars, and the L88 was no exception. But asCorvette News noted in an exercise in understatement, "The L88 is not anengine for ordinary everyday driving. It gives a rough idle, is not theeasiest engine to start, and was not designed with high fuel economy inmind."

Available from 1967 through 1969, L88 Corvettes were limited-editionautomobiles. (The L88 option was priced at $947.90 in 1967 and 1968, andat $1,032.15 in 1969.) Only 20 were produced the first year, 80 in 1968,and 116 in 1969. However, quite a few L88 engines were purchased overthe parts counter, so there are probably now more "L88 Corvettes" inexistence than were ever produced by General Motors.

ZL1: The First Aluminum Big-Block

The infamous '69 ZL1 was the... 

   

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The infamous '69 ZL1 was the ultimate big-block . Unfortunately, onlytwo documented production-line cars were reputed to have been built,primarily due the extreme cost ($4,718) of the option.

It borders on blasphemy to talk about infamous Corvette big-blockswithout including the ZL1, but this engine's impact on Corvette enginehistory is minimal since only two documented vehicles were everproduced. The ZL1 was simply an L88 with an aluminum block and a $4,718price tag. Although it's considerably lighter than its cast-ironcounterpart, the ZL1 didn't produce any more power. (See L88 above.)

LS6: The Last Corvette Big-Block

1970 was the first year for... 

   

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1970 was the first year for the 454. Available in LS-5 form (390 horse) or LS-6 form (450 horse) it would be the last big block in a Corvette.

Although 1971 was the first year of reduced compression ratios, it wasalso the first year--and last--for a solid-lifter version of the 454ci(4.251-inch bore, 4-inch stroke) big-block. Wearing option RPO LS6, itwas rated at 425 hp at 5,600 rpm and sported aluminum cylinder heads, a9:1 compression ratio, an aluminum intake manifold, and an 800-cfmHolley four-barrel. Other niceties included a cross-drilled, nitridedcrankshaft, domed pistons, and a $1,220.70 price tag.

In essence, the LS6 was a streetable version of the L88. The increase instroke somewhat offset the loss of compression ratio, so all in all theLS6 was a better engine for non-racing use. And in spite of emissionsregulations and all the other baggage that Detroit had to carry in theearly '70s, the LS6's 425 hp (325 net) was underrated.

Some would argue that the LS7 should occupy this space, but although theengine was announced and specifications printed, the LS7 was neverinstalled in a production Corvette.

Legendary Big-Blocks