History And Mystery Of The Rarest Chevy Chevelle In Existence

Summary

• The LS6 option was the most powerful, with a 454 cubic-inch engine delivering 450 HP and 500 pound-feet of torque, set apart from the LS5 option.
• Identifying an authentic LS6 Chevelle is challenging given the lack of production numbers, but VIN decoding and specific components can provide proof of authenticity.

Arguably known in the muscle car world as the “King of the Muscle Cars,” the 1970 Chevy Chevelle SS 454 LS6 is one of the most sought-after vehicles of the era. A limited number of only 4,475 Chevelles were optioned as the SS 454 with the factory-packed LS6 upgrade. Chevy dropped their high-powered LS6 into three Chevy Chevelle models, which included the coupe, the convertible, and the El Camino.

However, the exact division between how many of each received the high-horse version of the 454 cubic-inch powerhouse was undocumented, or as Hemmings put it, a known unknown. Estimations vary, but there is some consensus that approximately 20 to 25 drop tops are in existence today, which makes finding an intact, numbers-matching example an extraordinary treasure and marks the 1970 Chevelle SS 454 LS6 Convertible the rarest of all Chevelles.

In order to give you the most up-to-date and accurate information possible, the data used to compile this article was sourced from various manufacturer websites and other authoritative sources, including General Motors, GM Heritage, MotorTrend and the LS6 Registry.

The LS6 Upgrade Is What Makes The 1970 Chevelle SS 454 So Rare

In 1970, the Chevelle Super Sport was available as either the SS 396 (RPO Z25) or the SS 454 (RPO Z15). Both SS versions were dressed with a blacked-out grille and an SS emblem swapped in place of the Chevy bow-tie The bow-tie could still be found front and center on the Malibu series, but was deleted from the Chevelle base trim.

In 1970, The 454 Cubic-Inch Engine Was The Largest Chevy Had Used To Date

The RPO Z15 featured a 454 cubic-inch beast that was the biggest, most pumped-up power plant that Chevy had ever stuffed into a production passenger car’s engine bay. Within the SS 454 order, there were two choices. One was the standard LS5 and the other was an upgrade to the LS6. Both represented a cast-iron block. However, the LS5 had a two-bolt main vs. the beefier-bottomed four-bolt main on the LS6.

1970 Chevelle Turbo-Jet 454 V8 LS6 Engine Specs

(Source: Chevrolet)

The LS5 And LS6 Had Their Differences In the Chevelle SS 454

A Special Ducted Hood (RPO ZL2) was available with all the SS options. Choosing ZL2 included stout, functional hood pins and locks that bookended both sides of the hood. The cowl-induction hood force-fed cold air into the LS6’s standard Holley four-barrel carburetor that topped the Winters aluminum intake manifold. The branded intake is identifiable by the cast snowflake.

The 1970 model year was the only one to utilize the Holley carb and aluminum intake. On the other hand, the LS5 included a cast-iron intake manifold with a Rochester Quadra-Jet carburetor. The LS6’s two heavy-duty transmission options were the manual Muncie four-speed (RPO M22) or the three-speed automatic Tubro-Hydromatic TH400 (RPO M40). The LS5 was given a lighter-duty tranny.

AMA Documentation Serves A Deeper Dive Into The LS6

For those looking further into the LS6, the American Manufacturers Association (AMA) Specification Sheets issued on October 15, 1969, verifies there were three versions of the General Motors 1970 model year Chevelle equipped with the Turbo-Jet 454 V-8 LS6. Two five-passenger vehicles, the coupe, (13,637) and the convertible (13,667), in addition to the three-passenger, two-door sedan pickup, known as the El Camino (13,680) complete the list.

1970 Chevy Chevelle SS 454 Coupe Specs

The LS6 within these three examples was rated for a published 450 horsepower at 5,600 RPM and 500 pound-feet of torque at 3600 RPM. During this specific time in hot rod history, the disconnect between published horsepower ratings and actual horsepower ratings is fairly common knowledge.

The well-known reason for the underrated horsepower points to automakers attempting to keep insurance companies in the dark about the engines’ real output. However, it becomes a glaring standout when the AMA specs actually document the phrase “PUBLISHED” MAX BHP” as opposed to simply horsepower.

Identifying A True ’70 Chevelle SS 454 LS6 Is a Challenge

With Chevy’s lacking production numbers, the high value of the Chevelle SS, and the challenge of proof, a real-deal 454 SS LS6’s authenticity comes into question. There isn’t one surefire way to identify an LS6-ordered SS. Build sheets, and original purchase paperwork such as the Chevrolet Owner Protection Plan (Protect-O-Plate) is the most straightforward method.

Most often, those items are not available and other identifiers such as Vehicle Identification Number (VIN), casting numbers, and actual components on a Chevelle will be pieced together to judge potential authenticity.

But for those fortunate to come across a true LS6 ’70 Chevelle, it is quite the find. In fact, a 1970 Chevelle SS 454 LS6 is such a treasure, that experts value a documented version, depending on condition, in the hundreds-thousands or more. One of the coveted 1970 Super Sport Chevelles has even sold for over a million.

A VIN Decoder Is A Good Start To Chevelle Identification

As seen in the Barret Jackson video above, it is important to underline the fact that a VIN alone is not always sufficient evidence to prove a true SS 454 with an original LS6. Much more fact-finding could be required. However, it is a good starting point and provides some history of a vehicle before a restoration begins. A restoration guide such as the E-Book Chevelle Restoration And Authenticity Guide: 1970 – 1972 is helpful with matching parts, casting numbers, and labels such as the Emission Control Label number with photos.

This 1970 Chevelle SS 545 LS6 Convertible Underwent A Top Bottom Restoration

The 1970 Chevrolet SS 454 Convertible shown in the photos above is an example of a restoration with a non-numbers-matching 454 cubic-inch LS6 V-8. It is not documented in the LS6 Registry, but less than 10 percent of the 4,475 Chevelle models manufactured with the 454 LS6 have surfaced and registered with the LS6 Registry.

Decoding A RestoMod’s VIN And Fender Tag

An examination of this Chevelle’s Vehicle Identification Number (VIN) with a VIN Decoder will reveal the basics of the car’s original details. A closer look at this particular soft top, Super Sport’s VIN 136670B****** translates this info:

The Fender Tag is another tell-tale history of any car. This restored Chevelle’s Fender Tag reveals several matches to its VIN.

Although it’s not a number-matching 454 cubic-inch LS6 V-8, the big block buried inside is branded with 3963512 – an era-correct casting number. The factory-color preservation of this unit continued with a redo of the Chevelle’s Tuxedo Black exterior and red interior. Performance-wise, this Super Sport was mated to a Muncie M22 Rock Crusher four-speed manual transmission and built on a factory-accurate chassis with a 12-bolt posi rear end.

The Components That Completed This ’70 Chevelle Restoration

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

Locating any of the currently undocumented units from any model of the original pool of LS6-powered SS Chevelles is a hunt akin to seeking a needle in a haystack. Uncovering a rag-top version is even more like unearthing a unicorn. It is likely that a good chunk of the ’70 SS 454s have met their demise in the more than five decades that have passed since their reveal and every passing year lessens the probability of discovery. Although their numbers are constantly in decline, interest in the legendary iconic Chevy muscle car continues to grow.