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Detroit sold millions of cars in 1970. Most were boring: six-cylinder Plymouth Valiants, base-model Mercury Montegos, and even some 307-powered four-door Novas and Chevelles. In addition, Detroit produced Hemi 'Cudas, Z28s, Boss 302s, GSXs, 442s, 440 Six-Pack Challengers and hyper-winged Charger Daytonas. The year 1970 was the very best year for musclecars. But at the track, those 'Cudas, Camaros, Mustangs, Buicks, Oldsmobiles, Daytonas and Superbirds were getting whooped by the Chevrolet SS454 Chevelle powered by the LS6 big-block engine. The LS6 Chevelle is the greatest musclecar ever built for one simple reason: it was the fastest mid-sized, big-engine musclecar ever built---period.
It's easy to misunderstand the greatness of the LS6. With so much concentration on the engine, it's easy to overlook the Chevelle itself, and the fact that the '70 Chevelle actually enhanced the LS6's efficiency. We're talking about a complete package; a car that handled, stopped, rode and drove as well as any during its era. It was the seventh year of production doe the A-body Chevelle, with a beautifully balanced all-coil sprung, splayed four-link rear and A-arm front suspension. The Chevelle had never been as comfortable or as competent as the '70 model. That the LS6 was smart-looking and brutally quick just made it better.
The LS6 was the culmination of a natural Chevelle evolution that started in 1965 when Chevy knocked out the 201 Z16 375hp, SS396 Malibu coupes. Intended to stomp the GTO, the Z16 did just that, but was also more civilized and sophisticated than the Goat. The Z16 simultaneously introduced big-block power and the idea of a mature musclecar. The big-block became a regular production item in '66 Chevelles, and the SS396 quickly became the best selling of all the musclecars right through the '69 model year.
It's unfair to call the SS396 Chevelle slow, but it had a hard time keeping up with Ford and Chrysler competition. When Motor Trend magazine tested a '68 SS396 against everything from a 390-powered Ford Torino to a 440 Dodge Charger, the 350hp SS396 was the slowest of the eight-car group. The Chevelle's 15.8 second quarter-mile e.t. left it nearly a full second slower than the Charger, and more than half a second behind the Torino with six fewer cubes. Even the 375hp L78 396s had a hard time keeping up.
What was holding the Chevelle SS back was GM's rule demanding that no engine be bigger than 400 inches in a midsize car. In 1969, the potential of a larger engine in the midsize Chevy was obvious as 323 special-order COPO Chevelles were being powered by the Corvette's 425hp L72 427ci big-block (99 of these cars went to Yenko for cosmetic conversion). In some ways these '69 COPO cars were the prototypes of the '70 bigger-block Chevelles to come.
When GM dropped its 400-inch ban, everyone knew the '70 Chevelle SS would finally get the displacement it deserved. What no one was expecting was the LS6; an engine which exaggerated its displacement it advantage with the addition of a solid lifter valvetrain, a Holley carb big enough to suck low-flying Cessnas and a stout block with four-bolt main caps.
The 454ci LS6 engine was essentially the L72 417 with an extra 27 cubic inches of displacement. The crankshaft was forged from tough 5140 alloy steel and Tuffrided, cross-drilled and balanced. Attached to the crank were a set of Manafluxed, forged connecting rods whose 7/16-inch bolts were a 1/16-inch larger than those in the 454 SS base LS5 motor. And atop those rods were TRW aluminum pistons shaped to produce a crushing 11.25:1 compression ratio.
As rugged as the bottom end was, it was the deep breathing heads and atmosphere-emptying induction system that made the LS6's power. The large, rectangular ports contrasted the LS5's less efficient oval ports and were fed by massive 2.19-inch intake valves, and spat out past 1.88-inch exhaust valves. Sending air and fuel to the valves was an LS6 specific low-rise aluminum intake manifold and a monstrous 780cfm Holley. The one weak point in the LS6's assault was a set of constrictive cast iron exhaust manifolds.
Chevy rated the LS6 at 450hp at 5600 rpm and a devastating 500 lb-ft of torque at 3600 rpm. It would be the highest output rating Chevy has ever attributed to one of its engines---even greater than the legendary L72 and the exotic all-aluminum ZL-1 427. In fact the only Chevy engine that comes close is the current LT5 found only in ZR-1 the Corvette. The ZR-1 engine is rated at 405hp at 5800 rpm and 385 lb-ft of torque at 5200 rpm, using the SAE net rating method, which is far more conservative than were the gross ratings where the LS6's output was determined.
Ordering an LS6 was easy. A premium of $503.45 more than the price of a regular '70 Malibu hardtop, convertible or El Camino bought the Z15 SS 454 package which included all the expected SS396 pieces and parts, plus an extra 58 ci of displacement (it actually added another 52, but that's another story). The more common, LS5 SS454 produced 360hp from its 10.25:1 compression ratio, oval port, cast-iron intake manifold-with-a-Q-Jet Mark IV big-block assembly. Throwing yet another $263.30 at the Chevy dealer was to bump you up to the LS6 class. Past that, every regular production option was available on an LS6 except air-conditioning. Three different types of air cleaners were used on the LS6; an open element, a dual snorkel, or the sealed-to-the-hood version used in conjunction with the infamous ZL2 cowl-induction hood. Behind the LS6, buyers could order wither a Muncie M22 high-performance four-speed manual or a Turbo Hydramatic 400 three-speed automatic. Behind either transmission was a beefy 12-bolt rearend carrying Posi traction gears ranging from 3.31 to 4.10:1.
A little known fact peculiar to the '70 SS454 is that when whoever was responsible for encoding the production computer got around to programming the Z15 option, they left off RPO B22, which would have put "SS" insignia on the inside door panels instead of regular "Malibu" script. The result is that roughly 9 out of 10 '70 SS454s have "Malibu" on their door panels, while all SS396s have "SS." If you own one, you might check yours to see.
Since the '70 model year was plagued by a nasty UAW strike, the SS454 didn't go into production until almost October 1969, and the LS6 didn't appear until December. But when the first LS6 prototypes fell into the hands of journalists, the effect was electrifying. Motor Trend magazine compared the LS6 to a 440 six-pack Road Runner and a 429-powered Torino Cobra and found the Chevelle compelling. "we couldn't help but be impressed with the Chevelle," Motor Trend's A.B. Shaman wrote, "it was certainly the strongest---the most super---of the three."
Super indeed. Running the Turbo 400 and 3.31:1 gears, the LS6 managed to casually knock out a 13.8 at 97.5 mph run, and that's on the stock F70x14 Firestone wide-oval bias-ply tires. Putting that time in perspective, in the 46 years Motor Trend has been published, only a few 427 and ZR-1 Corvettes have been faster than that 4100 pound, bias-ply shod Chevelle. Car Craft magazine had another LS6, this one with a four-speed and 3.55:1 gears, and managed a 13.12 blast with a stunning 107.01 mph trap speed. As a Car Craft editor noted, "With good tires and some suspension work, the mid-12s should be no sweat."
Why there wasn't a run on Chevy dealers after word of the LS6's fabulous performance ranks right up there with the question of Jimmy Hoffa's whereabouts. Records from GM's Tonnawanda engine plant, where all big-blocks were assembled, show that only 4475 LS6 hardtops, convertibles and El Caminos were built during the '70 model year. Of that number, no one exactly knows how many were convertibles or El Caminos, but obviously those two body styles are rarer than the hardtop. The most reasonable estimate, according to Mark Meekins of the National Chevelle Owners Association, is that between 100 and 200 of the LS6s were convertibles.
While the LS6 was scheduled to go into the '70 Corvette (and even into the Camaro), it never made it. And by 1971 it disappeared from the Chevelle, even though a lower hp, lower compression version of the engine was used in the '71 Corvette. That makes the LS6 a one-year model, and the only time Chevy ever produced and sold a car more powerful than its own Corvette.
During the '70s, no one quite understood how special the classic musclecar era had been. But by the early '80s, those who grew up craving the cars began earning enough money to obtain them and the market took off. In no time the value of LS6 cars sky-rocketed even faster.
By the mid-80s a good LS6 hardtop was running nearly $50,000 *quite a bit more than the original price of approximately $4000), and convertibles were changing hands for between $150,000 and $170,000. Not too surprisingly, such incredible prices didn't last. When the economy nosedived later in the decade and in the early '90s, the prices of all musclecars dove with it. Today, a good LS6 hardtop costs around $20,000, an exceptional one can cost $30,000 and $35,000 and convertibles have sunk in price to between $50,000 and $70,000.
Stepping into a '70 LS6 in 1995 only confirms the car's greatness. Unlike other musclecar-era machinery, the car doesn't seem antiquated or addled in any significant manner. The brakes are horrid by contemporary standards, but the over-boosted steering is precise and the chassis is remarkably agile and composed over even the most bizarre road surfaces. Punching open the secondaries on the massive Holley is what transports drivers back to the days when emissions controls were proposals instead of realities. Except for the 488ci, V10-powered Dodge Viper, no new car has the low-end torque of an LS6. And compared to a Viper, at least the Chevelle has roll-up windows and a roof.
Its ability to generate insane velocities in a remarkably short time is what made the LS6 a legend. The fact that it's still contemporary as the century that created it dwindles toward its end is what makes it a great car.
Click here for the Myth of the Aluminum-headed LS6
What is it about the '70 Chevelle SS that makes it so eternally attractive? Even people who weren't yet born when the '70 Chevelle first hit the streets have an appreciation for it. And, among the aficionados of Chevy's popular A-body, there's a consensus that the '70 was, is, and always will be the greatest. Lets take a look at the elements that make it so.
The '70 Chevelle had clean lines and maybe they'll even be called classic someday. But the real appeal of the '70 Chevelle lies in the fact that it represents the absolute zenith of musclecar development. Let's face it, horsepower, and plenty of it, was what sold cars during the musclecar era. And, with the Chevelle, you could have as much as you wanted.
At the top of the engine option list was the 454/450hp LS6. Even back then, 450 horsepower right off the showroom floor was an awesome number. And the numbers it could generate on the dragstrip was equally awesome: ETs of 13.20s at over 105 mph were turned in regularly by enthusiast publications of the day, with speculation that slicks and decent rear gearing would put the Chevelle easily into the mid-12s. The LS6 had the highest factory horsepower rating ever offered for public consumption, and with performance figures like those, there was no doubt that all those horses were real.
Making that kind of power reliable and tractable is no small feat, but with five years of big-block production experience behind them, Chevrolet produced the parts needed to do just that. A four-bolt block fitted with a forged steel crank, heavy-duty rods and forged aluminum pistons ensured reliability, while a hot solid-lifter cam, large-port heads and a big Holley carb on an aluminum manifold helped make the power. Tractability? The LS6 would idle happily at 850 rpm, and taking it past the factory-imposed 6500 redline didn't even make the big rat breathe hard. A total of 4475 LS6 cars were built, including El Caminos and Monte Carlos.
Of course, there were other choices on the engine option list, including a tamer version of the 454. Rated at 360hp in the Chevelle (same engine carried a 390hp rating in the Corvette and full-sized cars), the LS5 was intended for people who liked the large displacement, but not the raucous nature of the LS6 (or the frequent tuneups and maintenance that went along with it). And while it sported the displacement and fender badges of Chevrolet's big-block, the hardware was considerably different from its high-horse brother. The LS5 used a two-bolt block as the foundation, although a steel crank still was attached to standard-duty rods. Cast pistons were specified, as was a hydraulic cam and oval-port heads. Fuel delivery was handled by a Quadrajet atop a cast iron intake. Production of the LS5 was pegged at 4298 units.
The SS396 Chevelle still reigned supreme, however, when it came down to overall production numbers. There were 53,599 396-powered Chevelles ordered in 1970 with the Super Sport equipment, 2144 of which were fitted with the 396/375hp (L78) option. The L78 was basically a downsized version of the LS6, and featured much of the same internal hardware. Demand for the L78 fell off dramatically, however, once the LS6 became available late in 1969. Today, the L78-powered Chevelles are even rarer and just as desirable to collectors as the LS6 cars. The base SS396 powerplant was now rated at 350hp as Chevrolet deleted the old 325hp version from the option list. Both 396s actually displaced 402 cubic inches as the result of a factory .030-inch overbore, but they still carried the 396 nomenclature so as not to confuse earlier marketing efforts. Somehow, SS402 just doesn't sound right anyway.
Packaging was plenty important, too, in 1970. And even though the Chevelle SS proved to be more than just another pretty face, it still had all the features that shouted musclecar. The '70 Chevelle had all the right bulges in all the right places. Wheel openings were accented with muscular flares, and the SS hood featured a dome large enough to contain everything that lurked beneath it. There was even an optional cowl induction package incorporated into the hood to help the big blocks breathe easier when they were called upon to lay the competition to waste. And if the body sculpting wasn't enough, a pair of bold stripes ran over the hood and down the trunk lid to signify that the Chevelle SS wasn't a car to trifled with. Other cosmetic additions included 14x7-inch spoked wheels shod with F70x14 rubber, bright wheel lip moldings, chrome exhaust extensions, a black rubber SS pad on the rear bumper and Super Sport badging on the grille and front fenders.
On the inside, special SS instrumentation was employed, and featured round gauges rather than the horizontal layout found in the Malibu. Likewise, special SS emblems could be found on the door panels and the center of the steering wheel.
Special upgraded underpinnings made the Chevelle SS a worthy road car, too. Power front disc brakes were standard items as were the F41 suspension. With a larger front sway bar, special suspension bushings, stiffer springs and shocks, and the addition of a rear sway bar, the Chevelle SS was as capable of turning corners as it was turning tires.
Hence the LS6 Chevelle was created. Chevy engineers passed over the 427 and developed two versions of a 454. The LS5 was the tamer with 360 horsepower while the LS6 pumped out a ground-thumping 450 horsepower. There was nothing gentle about the LS6: forged-steel crank, beefy rods with 7/16-inch bolts, 11:1 forged aluminum pistons, free-breathing rectangular-port heads, a wicked solid lifter camshaft that had seen duty in the 427 Corvette engines, aluminum intake manifold and an 800cfm Holley.
Drop the LS6 into the restyled '70 Chevelle Super Sport, mate it to a close-ratio M22 four-speed and a 4.10:1 Posi 12-bolt, lug on F70 tires at all four corners and top it all off with a bold-stripped ZL2 cowl-induction hood and you have the baddest Chevy ever built.