1970 Chevelle LS6 Cowl Hood Emblem
In the golden age of American muscle cars, specifically around 1970, there existed a distinct pecking order on the streets. At the top were the true “Big Dogs,” and then there was everyone else. Simply having a 400 cubic inch engine under the hood was no longer enough to dominate the impromptu stoplight drag races. The defining factor was raw horsepower; more power meant more cubic inches, translating directly to street supremacy. The old adage, “there’s no replacement for displacement,” was never more accurate than in 1970. And reigning supreme, perched at the very peak of this high-octane hierarchy, was Chevrolet’s Ss Chevelle. Not just any SS454 with a respectable 360 horsepower, but the undisputed heavyweight champion of the Bow Tie brand: the legendary RPO Z15. Ticking this option box unleashed a monstrous 450 horsepower, 454 cubic inch engine, a solid lifter beast that generated a staggering 500 lbs.-ft. of torque. This engine was built to conquer, leaving any challengers in its wake and firmly establishing its claim as the undisputed “King of the Streets.”
Chevelle LS6 vs Hemi
While road tests of the era were conducted using both four-speed manual and automatic transmissions, the performance figures were remarkably similar. However, street racers quickly learned that removing the factory-installed smog equipment, adding performance headers, and making minor timing adjustments could dramatically improve performance. Both transmission configurations were capable of leaving lesser muscle cars far behind. In a direct showdown between the LS6 Chevelle and its rivals, victory often depended more on driver skill than any inherent mechanical advantage. Chevrolet, surprisingly, had been somewhat slow to react when the muscle car craze exploded in 1964. While Pontiac had set a bold precedent by installing a 389 cubic inch Bonneville engine into the mid-size LeMans, Chevrolet initially offered a maximum of 327 cubic inches for their newly introduced Malibu. The first big-block Chevelle emerged in 1965 as the “Z16,” boasting a 396 cubic inch, 375-horsepower engine, but production was limited to a mere 201 units. In 1966, the SS396 became an official option for the Chevelle, directly challenging the Pontiac GTO. It proved to be a popular choice, with 72,272 units sold compared to Pontiac’s 96,946. The SS396 continued through 1969, with the 396 engine as the sole powerplant, offered in three horsepower levels: a standard 325, and optional 350 or 375 horsepower versions.
For the 1970 model year, General Motors finally lifted the 400 cubic inch restriction on intermediate-sized cars. The four GM divisions producing muscle cars—Buick, Oldsmobile, Pontiac, and Chevrolet—wasted no time in fitting their largest engines into their respective models. Buick, Oldsmobile, and Pontiac selected their existing 455 cubic inch engines. Chevrolet, however, took a different approach, choosing to enlarge their already potent 427 to a massive 454 cubic inches. This resulted in two 454 engine options for the Chevelle: the hydraulic lifter LS5, rated at 360 horsepower, and the solid lifter LS6.
1970 Chevelle LS6 454 Engine
The 450 horsepower LS6 was officially the most powerful engine offered by any manufacturer in 1970. Its performance was further enhanced by the Cowl Induction system, which channeled cool, outside air directly into the massive 780 cfm Holley carburetor. While the LS6 shared the same robust block as the LS5, it incorporated significant upgrades. A high-performance 800-cfm Holley four-barrel carburetor, mounted on an aluminum intake manifold, replaced the Rochester Quadra Jet found on the LS5. The LS6 engine featured a strengthened lower end with four-bolt main bearing caps, a durable forged steel crankshaft and connecting rods, and high-compression forged aluminum pistons with an 11.25:1 compression ratio. To handle the LS6’s high 6500 RPM redline, deep groove accessory drive pulleys were essential to prevent belt slippage at high engine speeds. Ironically, the LS6, the pinnacle of performance, was also burdened with early emissions control technology. New Federal emission standards mandated the inclusion of a primitive Air Injection Reactor (A.I.R.) pump. This system, plumbed into the exhaust manifolds, injected additional air into the exhaust stream to promote further combustion of unburned hydrocarbons and carbon monoxide. Interestingly, only the Holley-equipped LS6 received the A.I.R. system, and it was frequently one of the first components to be removed by performance-minded owners immediately after taking delivery of their new Chevelle.
Transmission choices for the LS6 Chevelle included either the close-ratio Muncie M22 “Rock Crusher” four-speed manual transmission, renowned for its strength and durability, or the three-speed M40 Turbo Hydra-Matic automatic transmission, offering a balance of performance and convenience. Rear axle ratios were available up to a very aggressive 4.33:1, and a limited-slip differential was also an option for improved traction.
1970 Chevelle LS6 Rear
Ordering an LS6 SS Chevelle was not a simple matter of selecting the engine. It required the buyer to also choose a set of mandatory options, making it a relatively expensive proposition. The RPO Z15 SS 454 package itself cost $503.45 and included visual and performance enhancements. These included bright engine trim, dual exhaust with polished tips, a black-painted grille, wheel opening moldings, power-assisted front disc brakes, a specialized rear suspension system, and F70 x 14 tires mounted on wider 7-inch rims. The rear bumper featured a distinctive black insert, and the front end was characterized by the signature “power bulge” hood. The base 360 horsepower LS5 engine and a heavy-duty battery were also part of the Z15 package. From this starting point, the buyer could then select the ultimate RPO LS6 454 engine, which added another $263.30 to the price. Transmission choices further impacted the bottom line, with the M22 manual adding $221.80 and the M40 automatic costing $290.40. Just to acquire Chevrolet’s most formidable street machine required spending at least an additional $988.55 on top of the base Chevelle price, which was just over $2,800. By the time a buyer added other desirable options, a fully loaded SS 454 Chevelle could easily exceed $4,000, a significant sum for the time.
1970 Chevelle LS6 Interior
The SS Chevelle’s interior was a step above the standard Chevelle and Malibu models, borrowing the attractive instrument panel design directly from the upscale Chevrolet Monte Carlo. The standard interior configuration included a bench seat, regardless of the transmission choice. However, buyers could opt for optional bucket seats, which also made a center console available. Unlike many other car manufacturers who used a common dashboard design across different trim levels, the 1970 SS Chevelle received a unique instrument panel. This distinctive, flat-faced panel housed a comprehensive gauge package featuring three large, circular openings for the tachometer, speedometer, and clock, with smaller ancillary gauges flanking them. To the right of the instrument cluster were the controls for the HVAC system, the radio, and the cigarette lighter.
The exterior styling of the SS 454 Chevelle was marked by sculpted lines above the wheel arches, giving the car a lower, more aggressive stance. The blacked-out grille was divided horizontally and prominently featured a large “SS” emblem in the center. Chevrolet offered bold “Stereo Stripes” as an option, running the length of the hood and decklid, further emphasizing the car’s performance intentions. The functional Cowl Induction hood was also a key visual feature, incorporating a vacuum-operated door at the rear of the hood. This system drew cool, high-pressure air from the base of the windshield and ducted it directly to the large Holley carburetor, enhancing engine performance.
1970 Chevelle LS6 Headlamp Detail
Dual Guide T-3 headlamps provided bright illumination and were framed by polished chrome bezels.
1970 Chevelle LS6 Tail Light Close Up
Bright chrome extensions on the tailpipes signaled the presence of the LS6’s powerful and sonorous dual exhaust system. While precise production figures are somewhat elusive, it is generally accepted that Chevrolet produced approximately 4,475 LS6 Chevelles in 1970. However, detailed breakdowns differentiating between coupe, convertible, and El Camino body styles within that total are not readily available. One of these coveted coupes is a Cranberry Red example owned by Rob Timken of Clearwater, Florida. This particular LS6, built in Arlington, Texas, has spent the majority of its life in the Florida climate, enjoying a pampered existence. In November 1992, Rob spotted the car in a hotel parking lot during a car show. Discovering that the owner was considering selling, Rob quickly negotiated a deal. He was particularly impressed by the car’s remarkable originality, its desirable options, and its low mileage, envisioning it as the perfect “fun car” to enjoy.
Despite the fact that his 66,000-mile LS6 was already in exceptional, almost pristine condition, Rob’s inherent perfectionism led him to undertake some careful rebuilding and detailing. “I spent time over the years,” Rob recounted, “painting and detailing the car and rebuilding the engine.” He opted for a conservative 0.30 cleanup bore during the engine rebuild, maintaining the original compression ratio and utilizing as many original parts as possible. Before reinstalling the rebuilt engine, Rob had it dyno tested, where it impressively produced 485 horsepower and 513 lb.-ft. of torque, exceeding its factory rating.
The interior was treated to new upholstery and carpeting, along with the installation of a new-old-stock (NOS) center console plate and sport steering wheel. The car’s extensive option list includes a tilt steering column, power steering and brakes, door edge guards, the desirable Rally gauge cluster, the Cowl Induction hood and stripes, bucket seats, a center console, and an AM radio.
In the 13 years that Rob has owned this remarkable LS6 Chevelle, he has added just over 1,800 miles to the odometer. While he doesn’t drive it frequently, when he does, he thoroughly enjoys the immense torque of the LS6 engine and the exhilarating, instant acceleration that only the true “King of the Streets” can deliver.
1970 Chevrolet Chevelle SS 454 LS6 High Exterior
Hood pins, the distinctive Cowl Induction hood, prominent SS454 emblems, and bold “Stereo Stripes” all contributed to the SS Chevelle’s undeniably muscular and aggressive appearance.
1970 Chevelle LS6 Trunk
The full-size spare tire occupies a significant portion of the trunk space, but still leaves room for essential items like a floor jack, tools, and jack stands, a nod to the car’s drag racing potential.
Text and Photos by Paul Zazarine © Car Collector magazine, LLC.
