The fleet of performance cars that came out of the 60s and 70s with the famous Chevy bowtie stamped on them is virtually endless. From meaty muscle cars like the Camaro to streamline sports cars like the Corvette, the choices were abundant. But when it came to the meatier performance cars that went above and beyond the rest of those in the muscle car market, nothing screamed Chevy performance quite like the 1970 Chevelle SS 454 LS6. A single-year option, this bowtie beast is so exclusive, in fact, that many enthusiasts still dream of owning one today.
The Chevrolet Chevelle made its debut just as the muscle car era was getting started. Introduced to compete with the Ford Fairlane, the Chevelle, however, still carried with it some odes to the past just like many early muscle cars, like the 115-inch wheelbase found previously on the famed Chevy Tri-Fives. But Chevy’s entrance into the muscle car world was not futile and the Chevelle quickly transformed from a bulky under-powered family car in early 1964 to a more sporty muscle machine starting just half a year later, thanks to the introduction of optional engines with more cubic inches.
By 1970, the Chevelle had seen the Malibu nameplate move to only certain models, undergone a couple of serious design overhauls and gained transmission and engine options to include 2, 3 and 4-speed gearboxes, as well as powerplants like the Chevy 350, 396, 400 and 402.
In 1970, Chevy was also offering its exclusive 454ci big block as an option on the Chevelle.
Available in sport coupe, sport sedan, four-door sedan, convertible, wagon and the El Camino “coupe utility” models, the 1970 Chevelles stood apart even from their previous model year siblings. This was thanks to sheet metal revisions that brought a more squared style to the muscle car’s body. While base models were certainly sold by the hundreds, performance enthusiasts flocked to the SS options, available only on the Malibu sport coupes, Malibu convertibles, El Caminos and wagons. Those opting for the SS upgrade could choose from two SS options- the RPO Z25 SS option with a beefed up 402ci engine (marketed as a 396 still), or the RPO Z15 SS option with Chevy’s 454ci big block. It was under the $503.45 RPO Z15 SS option that real performance connoisseurs could get the 454ci LS6 engine option.
In standard form, the RPO Z15-optioned Turbo-Jet 454ci (LS5) engine was rated at 360hp. The LS6, on the other hand, was rated at almost 100hp more (450hp) and capable of producing 500lb-ft of torque, although many believe the LS6 was highly underrated, especially when it came to horsepower. This option came at an even higher price, however, as the LS6 upgrade cost an additional $263.30 on top of the RPO Z15 upgrade in 1970, according to Hemmings.
What is known for sure, unlike exact power numbers, is that the LS6 option brought with it a 4.25-inch bore and a 4.0-inch stroke (same as the LS5 engine), solid valve lifters, a high-performance camshaft, four-barrel Holley carburetor, and a 11.25:1 compression ratio. The performance on the LS6 was upped even further with specialty heads, in contrast with the LS5’s cast-iron heads borrowed from the other 396ci engine, using 1.88-inch exhaust valves and 2.19-inch intake valves.
In addition to the added power and torque that the LS6 brought, all Z15-upgraded SS models (including those with the 360hp Turbo-Jet 454ci V8) received a heavy-duty suspension system complete with IFS and a live rear axle with a 4-link setup, dual exhaust with chrome tips, power front disc brakes, wheel arch moldings, a chrome rear bumper with black inserts and a black grille. This was on top of the quad headlamps, squared off headlight bezels, rectangular taillights and two-part grille design that was standard SS equipment, from the 396ci variety up.
An open 12-bolt rearend was standard on the 454ci SS cars, as were 3.31 rearend gears, although a Positraction rearend with the same gears was a factory option and a Positraction with 4.10 rearend gears a dealer upgrade. In addition to the standard Muncie M22 Rock Crusher four-speed closed-ratio manual transmission, 454 SS models could also be purchased with options like a heavy-duty clutch or a three-speed automatic transmission.
For an even more performance oriented Chevelle SS, the $147.45 ZL2 package was also available in 1970 as an upgrade to SS models, which included a cowl induction hood with vacuum actuated hood opening and functional hood pins, as well as hood and rear deck striping. It is this package that gave the Chevelle SS models their famed racing stripes and aggressive hood design.
Factory standard Chevelle SS 454 LS6 models were reported to be able to accelerate from zero to 60mph in just over 6 seconds. Even today, they continue to break the 12 and 13-second quarter mile marks on tracks all across the country.
The LS6 engine option was intended to continue on as an option in 1971, but was dropped prior to being put in any 1971 Chevelle models. Reports state that the LS6 option was available on 1971 models but was canceled in May of that year, with just 14 LS6 engines having been produced for the Chevelle that never made it into factory cars. It is because of this that the 1970 LS6-equipped cars are that much more intriguing and collectible still to this day.
Documented as one of the greatest Chevelles ever produced, the 1970 Chevelle SS 454 LS6 model was the highest powered Chevelle manufactured in the model’s lifetime, which ran from 1964 through 1977, and was the only GM car at the time to have ever topped the horsepower rating of the Corvette.
Even with up to a reported 4,475 LS6 models said to have left the factory floor for the 1970 model year (reported production numbers are inconsistent at best), LS6 Chevelles remain highly sought-after collectors items. Even those that are undocumented LS6 models have been known to sell for over $150,000 like the convertible sold this year at the Barrett-Jackson Las Vegas Auction for $178,200. Others that sold at Barrett-Jackson auctions in 2013 ranged in price from $88,000 to $258,500. Even clones can go for big money, with some selling well within the $80,000 to $90,000 range at premiere events.
We can go on and on about what any particular car brings to the table compared to its competition, but when it comes to performance Chevys born in the muscle car era, the 1970 Chevelle SS 454 LS6 is definitely at the top of the influential list. Not only did it make history with its power numbers and available options, the car still remains an icon some 40 years later. And if that’s not a key to deciding muscle cars you should know, we don’t know what is!