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St. Louis, MissouriChevelle/Corvette 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 lbf-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 lbf-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 have 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!
Note the routing of the PCV hose in the photo above. This is indicative of an LS6 built at the Arlington, TX. assembly plant. Learn more interesting details in the new book, Chevelle Restoration and Authenticity Guide 1970-1972, co-authored by Dale McIntosh (webmaster here) and Rick Nelson of Musclecar Restoration & Design.
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.
Update: March 1, 2019. It has been reported to the webmaster there may be an earlier, documented LS6 than the one mentioned above. To date the owner has not come forward to the LS6 Registry with any information on the car.
Introduction of the Z15 Option
It appears the Richmond Zone Office notified its dealers of the Z15 option before GM released their service bulletin.
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 is 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..." The GM Service Bulletin is dated November 20, 1969.
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, but former Tonawanda officials claim no LS6 was ever built with the L89 aluminum head option.
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 & 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.
The LS6 engine was an option on top of the Z15 "SS454" option. One of two transmissions were mandatory, the H.D. Muncie 4-speed under RPO M22 or the H.D. Turbo Hydra-Matic 400 under RPO M40. The metal ID plate on the TH400 can only be coded CY.
One of three rear ends were required with the LS6 engine option;
the two 3.31:1 rear ends were shared with the base LS5 engine (CRU
and CRV), only the LS6 could be ordered with the CRW 4.10:1 Positraction
rear end.
CRU - 3.31:1 open
CRV - 3.31:1 Positraction
CRW
- 4.10:1 Positraction.
1971 Corvette LS6
Strangely enough, the 1970 Corvette's biggest engine was the 390hp LS5. The LS6 was an option in 1971, but only 188 were sold with a horsepower rating of 425hp.
