1970 Chevy Chevelle Convertible: The Ultra-Rare LS6

The pantheon of American muscle cars holds a special place for the Chevrolet Chevelle, particularly the 1970 model year. Among these automotive legends, the 1970 Chevelle SS 454 LS6 stands out, often hailed as the “King of the Muscle Cars.” While impressive in any form, the 1970 Chevy Chevelle Convertible equipped with the mighty LS6 engine achieves mythical status due to its extreme rarity. Chevrolet produced only 4,475 Chevelles across all body styles (coupe, convertible, El Camino) with the LS6 option package. However, the exact number of convertibles built with this powerhouse remains officially undocumented—a “known unknown.” Current estimates suggest only 20 to 25 original LS6 convertibles exist today, making a verifiable, numbers-matching example an incredibly sought-after and valuable piece of automotive history.

The Heart of the Legend: The LS6 Engine Upgrade

In 1970, buyers seeking peak performance could option their Chevelle Super Sport with either the SS 396 (RPO Z25) or the ultimate SS 454 (RPO Z15). Both packages featured aggressive styling cues like a blacked-out grille proudly displaying the SS emblem instead of the standard Chevrolet bow-tie found on the Malibu series.

Close-up view inside the engine bay of a 1970 Chevy Chevelle SS 454, highlighting the powerful big-block V8 engine.

SS 454 vs. SS 396: Setting the Stage

While the SS 396 offered potent performance, the RPO Z15 package introduced the formidable 454 cubic-inch V8, the largest displacement engine Chevrolet had ever installed in a production passenger car up to that point. This big-block power plant set the stage for legendary performance figures.

LS6 vs. LS5: Key Differences in the 454

Ordering the SS 454 presented a further choice: the standard LS5 engine or the high-performance LS6 upgrade. Both were cast-iron Mark IV big blocks, but crucial differences set them apart. The LS5 utilized a two-bolt main bearing cap configuration, whereas the LS6 featured significantly stronger four-bolt mains, designed to handle higher stress and power output.

Engine Specifications (LS6)

The LS6 wasn’t just about displacement; it was a carefully engineered performance package:

(Source: Chevrolet)

Beyond the Block: Induction and Transmission

Further enhancing the LS6’s performance was the available Special Ducted Hood (RPO ZL2), also known as cowl induction. This functional hood scoop, secured by distinctive hood pins, force-fed cool ambient air directly into the LS6’s standard Holley 800-cfm four-barrel carburetor. This carburetor sat atop a Winters aluminum intake manifold, identifiable by its cast snowflake logo – components unique to the 1970 LS6. In contrast, the LS5 used a cast-iron intake manifold paired with a Rochester Quadra-Jet carburetor. Drivetrain choices for the LS6 were equally robust: the heavy-duty Muncie M22 “Rock Crusher” four-speed manual (RPO M22) or the Turbo-Hydramatic TH400 three-speed automatic (RPO M40). The LS5 received lighter-duty transmission options.

Official Specs and the Horsepower Mystery

Delving deeper into the LS6’s specifics requires looking at official documentation from the era.

Aerial view of the engine bay in a 1970 Chevelle SS 454 LS6, showcasing the Turbo-Jet 454 V8 with its distinctive components.

AMA Documentation Confirms LS6 Models

American Manufacturers Association (AMA) Specification Sheets dated October 15, 1969, confirm that General Motors offered the Turbo-Jet 454 V-8 LS6 engine in three 1970 Chevelle models: the five-passenger coupe (model 13637), the five-passenger 1970 Chevy Chevelle Convertible (model 13667), and the three-passenger El Camino pickup (model 13680).

The Underrated Power Phenomenon

The AMA documents list the LS6’s output as 450 horsepower at 5,600 RPM and 500 lb-ft of torque at 3,600 RPM. However, it’s widely accepted among muscle car historians that manufacturers during this period often deliberately underrated horsepower figures, partly to appease insurance companies wary of high-performance vehicles. Tellingly, the AMA specifications use the exact phrase “PUBLISHED MAX BHP,” hinting that the engine’s actual output might have been considerably higher, potentially exceeding 500 horsepower in reality.

Identifying a Genuine 1970 Chevelle Convertible LS6

Given the lack of precise production breakdowns from Chevrolet, the immense value associated with authentic SS 454 LS6 models, and the ease with which standard Chevelles could be cloned into SS lookalikes, verifying a true LS6, especially a 1970 chevy chevelle convertible, presents a significant challenge.

A black 1970 Chevrolet Chevelle SS performing a burnout, demonstrating the raw power associated with this classic muscle car.

The Authentication Challenge

There is no single, definitive method to confirm an original LS6 Chevelle SS without irrefutable provenance. The most reliable proof comes from original factory documentation, such as the build sheet (often found atop the gas tank or under the seats) or the Chevrolet Owner Protection Plan booklet containing the Protect-O-Plate metal tag.

Using VIN Decoders and Build Sheets

Often, original paperwork is lost to time. In its absence, authenticators must piece together evidence from various sources. Decoding the Vehicle Identification Number (VIN) provides basic information about the model year, assembly plant, body style, and original engine type (V8 vs. six-cylinder), but typically doesn’t specify the LS6 option directly for 1970 Chevelles. Cross-referencing casting numbers on the engine block, cylinder heads, intake manifold, and transmission case against known correct numbers for the LS6 package is crucial. Examining date codes on components ensures they align with the car’s assembly date. Fender tags also offer clues about original paint, trim, and build date. Resources like the Chevelle Restoration And Authenticity Guide: 1970 – 1972 and online registries like the LS6 Registry can be invaluable tools.

Value and Investment Potential

The difficulty in authentication underscores the immense value of a documented, numbers-matching 1970 Chevelle SS 454 LS6. Depending on condition, provenance, and body style, these cars command prices deep into six figures, with pristine convertible examples potentially exceeding seven figures at auction. One exceptionally rare 1970 chevy chevelle convertible SS 454 LS6 reportedly sold for over $1 million, solidifying its status as a blue-chip collectible muscle car.

Case Study: Restoring a 1970 Chevelle SS Convertible

The black 1970 Chevelle SS 454 Convertible featured in some photos serves as an example of a meticulous restoration. While this particular car houses an era-correct, non-numbers-matching LS6 V8 and is not documented in the official LS6 Registry, its restoration highlights the details involved in bringing these icons back to life. It’s worth noting that less than 10% of the original 4,475 LS6-equipped Chevelles have been registered, leaving many potentially undocumented.

Side profile of a stunning blue restored Chevrolet Chevelle, illustrating its potential as a classic car restoration project.

Decoding the VIN and Fender Tag (Example)

Examining this restored convertible’s VIN (136670B**) reveals:
| VIN Segment | Meaning |
| :———- | :———————– |
| 1 | Chevrolet |
| 3 | Chevelle |
| 6 | V8 Engine |
| 67 | 2-Door Convertible |
| 0 | 1970 Model Year |
| B | Baltimore Assembly Plant |
| ** | Sequential Unit Number |

Its Fender Tag provides further original details:
| Fender Tag Code | Meaning |
| :————– | :——————————————– |
| ST70 13667 | Style 1970, Chevelle 2-Door Convertible |
| B | Baltimore Assembly Plant |
| 300812 | Fisher Body Unit Number |
| PNT 19 B | Tuxedo Black Paint, Black Convertible Top |
| TRM 788 | Strato Bucket Seats, Custom Red Vinyl Interior |
| 96D | Assembled 4th Week Of June |

Key Components in the Restoration

This restoration aimed for factory accuracy where possible:

• Era-correct 454 cubic-inch LS6 V-8 (Casting # 3963512)
• Muncie M22 Rock Crusher Four-Speed Manual Transmission
• Factory Power Steering
• Power Front Disc and Rear Drum Brakes
• Fully-Functional Cowl Induction system
• Correct Holley Carburetor and Winter Intake
• Stock-style Exhaust System
• Reproduction Delco Battery
• Factory Accurate Chassis details
• 12-bolt Posi-Traction Rear End
• Correct Double A-Arm Front / 4-Link Rear Suspension
• 14-Inch SS Wheels with F70-14 Goodyear Polyglas Wide Tread Tires

The Ongoing Search for Originals

Finding any undocumented LS6 Chevelle is like searching for a needle in a haystack; uncovering an original 1970 chevy chevelle convertible LS6 is akin to finding a unicorn. As decades pass, the number of surviving examples inevitably dwindles, making each discovery more significant. Despite their scarcity, fascination with these legendary machines continues to grow.

A Brief History of the Iconic Chevy Chevelle

The Chevrolet Chevelle played a pivotal role in the muscle car era, produced over three generations from 1964 to 1977. It became one of GM’s most successful nameplates, solidifying Chevy’s performance image.

Comparison image showing an original 1970 Chevy Chevelle SS alongside the modern 2024 Chevelle 70SS interpretation by Trans Am Worldwide.

Generations and Body Styles

Available in various forms—including two-door hardtops, convertibles, four-door sedans, and even station wagons—the Chevelle offered broad appeal. It also spawned the popular El Camino coupe utility pickup. This versatility allowed it to serve as basic transportation, a family car, or, particularly with the SS package, a dominating force on the street and strip.

Rise and Fall of a Muscle Car King

The Chevelle peaked in popularity and performance around 1970. By its third generation (starting in 1973), tightening emissions regulations and shifting market demands led Chevrolet to drop the high-performance SS options after 1973. The Chevelle gradually transitioned into a more conventional mid-size car before production ceased after the 1977 model year.

Beyond the LS6: Other Rare Chevelle Gems

While the 1970 LS6 convertible might be the rarest, Chevrolet produced other limited-production Chevelles that are highly collectible today:

• 1967 Chevelle SS 396 L78 (612 Units): Equipped with the potent L78 version of the 396 V8, rated at 375 horsepower, significantly higher than the base SS 396 engine.
• 1967 El Camino/Chevelle L78 (612 Built): The same powerful L78 engine option was also available in the El Camino variant, with similarly limited production.
• 1965 Chevelle Malibu SS 396 Z16 (201 Units): A special package introducing the new 396 Turbo-Jet big block (L37 version) rated at 375 horsepower. Only 200 production models plus one prototype were built, with fewer than 75 known to survive today.
• 1969 Chevelle Yenko SC 427 (99 Units): Created by performance dealership Yenko Chevrolet using Chevrolet’s COPO system (Central Office Production Order 9562), these cars received the L72 427 big block V8, normally found in Corvettes, rated at 425 horsepower. Only 99 were produced.

An eye-catching orange 1970 Chevrolet Chevelle SS, reflecting the model's popular culture appearances in films.

The Enduring Legacy of the 1970 Chevelle Convertible LS6

The 1970 chevy chevelle convertible with the SS 454 LS6 package represents the absolute pinnacle of Chevrolet’s muscle car dominance. Its combination of brutal big-block power, aggressive styling, open-air driving experience, and extreme rarity secures its place among the most desirable and valuable American automobiles ever produced. Identifying and authenticating one remains a significant challenge, requiring deep expertise and thorough documentation. Yet, the pursuit continues, driven by the enduring allure of owning a true “King of the Muscle Cars.” For enthusiasts and collectors, the LS6 Chevelle convertible isn’t just a car; it’s a potent symbol of an era defined by horsepower and iconic design.