International 1970 Chevelle LS6 Registry - Tech & Trivia about the LS6

The awe inspiring 1970 Chevelle SS454 with the RPO LS6 engine option was the baddest of the bad. With a factory advertised 450 HP at 5600 RPMs and 500 lb-ft of torque at 3600 RPMs, it was the highest horsepower offered from Chevrolet in any Chevelle. The RPO LS6 option added $263.30 to the required Z15 SS454 option at $503.45. Due to the 500 lb-ft of torque, the LS6 also required either the M22 "Rock Crusher" Muncie 4-speed manual transmission at $221.80 or a special Turbo-Hydramatic 400 3-speed automatic transmission at $290.40. So, right off the bat you've committed between $988.55 and $1057.15 over the base price of a Malibu sport coupe, convertible, or Custom El Camino for the experience. And what an experience it would turn out to be!

File Photo

For your $503.45 for the RPO Z15 SS454 selection, you got the base 454/360HP LS5 engine, dual exhaust, a special domed hood, black accented grille, power disc brakes, sport wheels with wide oval tires, rear bumper pad (except El Camino), wheel well moldings, bright engine accents like chrome valve covers & air cleaner cover and special chassis features. Add to this $263.30 for the optional LS6 engine and one of the two mandatory transmissions.

Naturally other options were available to personalize your LS6 such as Instrument Panel gauges that included a water temperature gauge, amp gauge, clock and a 6500 redline tachometer, bucket seats, a console with floor mounted shifter for the TH400 automatic (the 4-speed was floor shifted with or without the console), a functional cowl induction hood that also included hood pins and the famous hood & deck stripe kit, Positraction rear axle, power steering and/or power brakes, tilt steering column, a selection of radios and even an 8-track stereo tape system. About the only comfort option not available on the LS6 was air conditioning.

Although the first known, documented, LS6 Chevelle was built at the Kansas City, MO. plant with a build sheet date of 11-19. most plants did not begin in earnest until early December.

Courtesy Dave Birdwell


This follow-up is generously provided by Mr. John Donchak

Fran Preve is the historian for the Tonawanda plant, I'm sure many on here either know or have heard of him. Anyway quite a few years ago he was authorized by GM to make copies of all plant and dealer production bulletins from back then. He graciously did some research for me earlier this year and confirmed a few things. Here's pretty much the timeline based on actual internal documentation - as opposed to the "GM did strange things" black hole of unverified claims.

The "Richmond letter" (shown above) as it's known was disseminated on 10-30-69 from Chevy to dealers stating: "...the 375-HP Engine Option L78 and the L78/L89 for use with SS 396 IS IN PROCESS of being cancelled..."

There is debate as to whether the L89 aluminum head option was offered on the new LS6.  Many say no and cite this sentence in the letter.  However, there are engine codes assigned to L89 optioned LS6 engines.  One such claimed LS6/L89 owner says the car was ordered as an L78/L89 but with the L78 was being discontinued the L78 option was crossed out and the LS6 option substituted.  The various documentation presented indicates the LS6 did come with the L89 optional heads and the warranty Protect-O-Plate card and dealer sales receipt showing the correct CRY engine suffix code.

(On) 11-7-69 a similar letter generated from the Charleston Zone stating:  "The L78 option IS BEING CANCELLED in view of the newly released 454 CID engines."

And finally on 11-20-69 a product bulletin stating: "With the release of the SS 454 engines, option Z25/L78 375 HP 396 V8, and option Z25/L78/L89 375 HP 396 V8 with aluminum cylinder heads "ARE NOW CANCELLED."

(On) 12-8-69 A plant bulletin was released stating " The LS6 engine is now in production."

While there were certainly a small handful of Chevelles rolling around facilities with LS6 engines prior to 12-8, these were R&D transplant 396 cars being emissions certified, as well as long lead press cars being evaluated by automotive journalists etc. These were crusher beta cars, not DOT certified, and never intended for production.

November, 2010:  This particular pilot car recently underwent a complete restoration back to exact assembly line condition by Rick Nelson and can be seen on his MuscleCar Restoration and Design website.

This particular Baltimore LS6 has been touted for a number of years as the "first" production LS6 but a Kansas City-built LS6 destined for a Canadian dealer has put this to rest. It may very well have been the first Baltimore-built LS6 for production (or at least the earliest known from Baltimore) but the Kansas City-built LS6 that, according to GM of Canada paperwork was exported to Canada was built on November 18 and shipped to Canada on November 25. Here's a link to the documentation on this car.