For its 1970 lineup, GM lifted the 400 cubic inch restriction on their intermediate models, and the four divisions that produced muscle cars immediately dropped in their biggest engines. Buick, Oldsmobile and Pontiac took the 455 engine off the shelf, while Chevy chose to punch out the venerable 427 to 454 cubic inches, offering the hydraulic-lifter LS5 rated at 360 horsepower and the solid-lifter LS6. The LS5 and LS6 shared the same block; however, a 800-cfm Holley four barrel bolted to an aluminum manifold replaced the venerable Rochester QuadraJet. The LS6 featured a robust bottom end with four-bolt mains, forged steel crankshaft and connecting rods with forged aluminum, 11.25:1 compression pistons. Chevy claimed a 450 gross HP rating in solid-lifter, high-compression guise. Many have suggested that the LS6 was substantially "under-rated" and produced something more on the order of 500 horsepower as delivered.
For the transmission either the Muncie M22 “Rock Crusher” close ratio four-speed manual transmission or the three-speed M40 Turbo Hydra-Matic automatic were available with rear gear choices up to 4.33:1 rear gears and limited slip differential.
The exterior of the SS 454 Chevelle featured sculptured lines above the wheel openings that pulled the car’s look downward. The grille was blacked out, split horizontally and received a large “SS” emblem dead center. Chevrolet offered wide, dual stripes that ran the length of the hood and deck lid and included a Cowl Induction system, which featured a vacuum-operated door at the rear of the SS hood. It stuffed air from the high-pressure area at the base of the windshield to that big Holley carburetor.
What makes this offering so special, however, is that the preserved original build sheet shows the original owner ordered it “stripe delete” and “cowl induction delete”, making this car more of a sleeper, without the bulkier hood and look-at-me racing stripes. Still, with the monster motor and the four-speed a skilled driver would be a street king in this car.
While it’s roundly agreed that Chevrolet produced 4,475 LS6 Chevelles, there is no breakdown to separate coupe, convertible and El Caminos in that total and speculation swirls to this day about how many LS6 convertibles were actually built. Many Chevelles were flogged gleefully into the ground by their owners and there are extremely few “original-survivor” LS6 models remaining, and far less restored cars than one would expect.
|---- Specifications ----|
|Engine||7.4 liter V8||Weight||--|
|HP/Liter||60.8 hp per liter||1/4 mile||--|
|0-62 mph||--||Top Speed||--|
This exceptional 1970 Chevrolet Chevelle LS6 convertible is rare in every sense of the word and has the build sheet to support it. The documented factory-production 13-second Chevelle LS6 is one of just 18 convertibles known to exist. Few were equipped with a 4-speed manual transmission like this one, and this unique car was ordered with stripe and cowl-induction delete, making it one of the rarest LS6s on the planet. This formidable and distinctive LS6 underwent a ground-up restoration when it was part of the Milt Robson Collection and shows just 50,356 miles on the odometer.
The Chevrolet Chevelle was a big hit with more than 440,000 produced in 1970. The ultimate Chevelle package occurred that same year as Chevrolet offered 450-horsepower worth of LS6 Turbo-Jet power to those willing to pay $263.30 for the factory 454-cubic-inch big-block engine. Fitting the car with an LS6 required options that backed up all that power with heavy-duty engineering and added nearly $1,000 to the base price. With that expense in mind, 4,475 Chevelle buyers chose the legendary LS6 engine. Only a tiny fraction of these were LS6-equipped Chevelle convertibles.
The build sheet for this rare LS6 convertible was discovered in the process of a comprehensive restoration. The documentation helps decode why this particular LS6 may represent the very zenith of American muscle car performance development, divulging that the original owner of this Medium Turquoise Metallic muscle car specified stripe and cowl-induction delete with a 4-speed manual to help the 454 deliver its wicked punch. It was as close as any Chevelle LS6 convertible could ever get to being a sleeper, and it was awesome, especially for the unsuspecting passenger who got the thrill ride of a lifetime.
With a Holley 4-barrel carburetor, aluminum dual-plane intake manifold and dual exhaust, the LS6 engine was conservatively rated for 450 horsepower and 500 lb-ft of torque. The 454 was prepared by the factory with a forged crankshaft and pistons with 4-bolt mains. A high-performance camshaft with solid lifters worked dual-sprung oversized valves in the cast-iron heads. The 6,500 RPM redline required deep-groove accessory pulleys. The engine is backed by a Muncie M22 Rock Crusher 4-speed manual transmission and heavy-duty 12-bolt rear axle for supercar-level factory performance that thrust the LS6-equipped 1970 Chevelle into the 13-second quarter-mile club right off the showroom floor.
High performance was not the only refinement to the Chevelle formula for 1970. More sculptured styling emphasized the sporty body lines. The horizontally split front grille featured 4-across headlights. The Super Sport package brought distinctive brightwork, a black-painted grille and SS badging. The code-34 Medium Turquoise Metallic paint is as it once was, returned to its original luster during the restoration. The car sports a power convertible top in white, which opens to a Parchment vinyl interior with optional Strato Bucket seats, pushbutton AM radio and a 4-speed floor-mount shifter proves to be the only subtle hint of the monster that lies under the hood.
The Super Sport package and LS6 engine together brought handling and traction improvements to the A-body platform SS454. The F41 suspension group packed heavy-duty coil springs, front and rear anti-sway bars, and box welded rear lower control arms. Power front disc brakes and power steering help control the horsepower. The Chevelle rides on 14x7-inch Super Sport wheels with SS center caps and Goodyear Polyglas tires.
The LS6 remains a legend to this day. It was a fire that burned brightest just prior to the flame being snuffed out on the original American high-performance era. This Chevelle LS6 convertible’s incredible combination of factory performance and distinctive options make it rare even amongst muscle car royalty.