Origin of "ZO6"

[Rich G.]

On ZO6vette.com, one of the younger members (I have socks older than most of these guys) asked about why a ZO6 is called a ZO6. Naturally, several more mature responders related the story of the 1963 Corvette and RPO ZO6.

So here's the question. Some of the commentors suggested the "Z" stood for ZORA. I had never heard this before, but often wondered how the RPO designations are picked. It seems they are common to classes of features. Or maybe not?

Comments?

Rich Giannotti 38594

[mike cobine]

Re: Origin of "ZO6"

Z = packages

Option numbers were in types, like L = engines, M = transmissions, P = tires and wheels, U = radio, and such.

Z28, remember? It was a package, which had a potent 302 ready to SCCA Trans Am race.

Z06 was a package. What was the one on the Impalas? Z11?

The rumor goes that the ZR1 and ZR2 were for Zora's Racer, and probably where the tale in your other group got started.

[Joe L.]

Re: Origin of "ZO6"

Rich-----

I think that someone's suggestion that the "Z" denoted Zora Duntov is "wild speculation". As a matter of fact, from the 1963 outset of the General Motors RPO designation system that's still in use today, "Z" prefix RPOs have designated "equipment PACKAGES". Initially, at least, I expect that the "suffix" portions of the RPO designation were assigned sequentially. So, there was once a Z01, a Z02, etc that were assigned for some other purpose. The Corvette package just got assigned Z06 in that "humble sort of way".

Most of the "Z" prefix "equipment packages" never became very famous. Most of them denote rather run-of-the-mill packages and, often, for appearance or convenience groups of options. There have neem a few other famous ones, though. Things like Z-28, ZR-1, and ZR-2.

Which brings up another subject. The RPO code assigned to the 1969 HD, all aluminum 427 engine, ZL-1, actually denotes an equipemnt package and NOT a specific engine in the normal RPO system. Engines were denoted with "L" prefixes in that system (and still are to this very day). So, how the engine ended up with this code, I don't know. While the engine required other options, they weren't supplied as part of a package. Even if the ZL-1 did refer to some sort of package, then the engine component of that package would have to have had an "L" prefix designation of its own. I've never been aware of one for that engine.

[Duke W.]

Re: Origin of "ZO6"

Z-prefix options are used for "special performance equipment packages", then and now. The current RPO system actually started in 1963. The previous system used three digit numeric codes. The new system for '63, which is still in use today, uses three digit alpha-numeric codes. Early on only one alpha character was used, but circa 1970 it expanded to two alpha characters, which increased the number of combinations.

Another Z-prefix option from 1963 was Z-11, which included the 409/425 and aluminum front end sheet metal for the full-sized Chevrolet. Another well known special performance equipment package is Z-28. These option numbers were only meant for internal use, but when "Z-28" became a performance moniker in the late sixties, GM marketing people recognized the marketing value of Z-prefix options and began to market the RPO designation on some models and options, and you see a lot of trucks around, nowadays, with "Z71 Offroad" body decals. (The dash between the letter(s) and numbers was dropped sometime in the seventies. Thus, the early nineties Corvette engine was designated "LT1" as opposed to the "LT-1" engine option in the early seventies.)

The 1963 Corvette Z-06 option was actually an esoteric designation that was only known amoung serious vintage Corvette enthusiasts before GM decided to resurrect it (without the dash) as the model designation for the highest performance Corvette model in 2001, They did a good job publicing the origin of the moniker, and probably fueled a price increase for the 199 original 1963 models equipped with Z-06.

I have no idea what happened to Z-01 through Z-05 or Z-07 through Z-10, but perhaps they were used for some planned special performance equipment packages that never made it to production, and then "reused" after time - like the 1975-6 Cosworth Vega package, which was RPO Z09.

As far a whether or not "Z" stands for "Zora", I highly doubt it being as how Duntov probably had no involvement in the development of the new production option designation system. No documentary proof exists, so I would just chalk it up to another urban myth.

Duke

[Joe L.]

Re: Origin of "ZO6"

Duke-----

The "Z" prefix was not limited to special performance equipment options; it was and is used for all sorts of non-performance equipment packages. In fact, special performance packages are a very small part of its use. The most common are TRIM packages. Also, unlike GM part numbers which are NEVER re-used or re-assigned, RPO designations ARE re-used and re-assigned. So, when speaking of a particular RPO designation, one has to take into consideration the year and model car.

As a matter of fact, the "Z06" RPO designation was used between the time that it was applied to the 1963 Corvette and the time that it was applied to the 2001 Corvette. What was it's last use before the 2001 Corvette performance package? From what I can tell, its last use was LUXURY INTERIOR TRIM for 1988 "G" body GM cars.

[mike cobine]

Re: Origin of "ZO6"

Joe, when we look at most RPO lists, they are usually in the Genuine Corvette Black Book or NCRS Corvette Specifications Guide format.

They leave out a lot.

In the salesman's booklet, the ZL1 is not listed as ZL1 but rather L88 ZL1.

This is similar to the L71 L89 engine (aluminum headed L71) except that the heads (L89) must have been viewed differently than the aluminum cylinder case.

Of course, the option read:

Engine, Special Corvette 427 V8 - incl. special hood & ornamentation. Positraction axle, special purpose suspension, full-transistor ignition system & HD power brakes req. (NA with power windows, power steering, or radio)

L88 With cast iron cylinder case .... 1032.15
L88 ZL1 With cast aluminum cylinder case ... 4718.35

As of 9-18-1969.

So maybe the L88 had really been the mislabelled option, in that being a package, it should have been Z88 or such.

And who knows the politics? In 1967, Z28 was the hot package to order in the Camaro, and many were figuring that out. But a 302 would get you in a lot less trouble than a 427, so maybe it was a conscious effort to NOT list the L88 as a Z- package knowing that people would pick the Z- under the assumption that it was the racing setup (which it would have been) even though they wouldn't be racing on a track.

After all, listing it as an engine (L88), it could be hidden with a lower HP rating and so the wannabees would pick and order the higher 435 hp and Chevy would be safe. You couldn't have hidden that Z- package.

All speculation on my part.

[Tom R.]

Re: It's not always about the engine

And let's now forget the less familiar Corvette suspension package "Z51" first introduced on the 1984 model and still available through C5 and whose predecessor was the Z07 heavy-duty suspension package. And an even lessor known "Z" non-performance package the ZN1 trailer package for Corvette from 1977-81.

[Warren F.]

Re: Origin of "ZO6"

The RPO options Z10 and Z11 refer to Camaro packages, the first being the regionally sold hardtop pace car option, the second the famous convertible pace car option, both for 1969.

[Duke W.]

Re: It's not always about the engine

Z51 includes both suspension pieces and a power steering cooler on C5. On C6 different tranmission ratios and tires are added. That's why is got a Z-prefix option. It's a "package" with upgrades to more than one system.

Z07 included both HD suspension components and the HD brake system.

Duke

[Tom B.]

Re: Origin of "ZO6"

One thing GM likes to do is recycle codes. The Z11 option on the Camaro is well known but in 1963 there was a Z11 Impala That was a 409 W motor taken out to 427 with the famous (if you are a W motor guy) Z11 cam. It was a last effort to make the W competitive before the 396 came out. Lots of guys put the Z11 cam in their 409s. It was very radical for the time.

Tom

[Tom P.]

Re: Origin of "ZO6"

As mentioned, the "Z" denoted packages. And the 63 Z11 was just that, a package. It came ONE way and one way ONLY. As mentioned, it was basically a 409 (BLOCK ONLY) that was stroked (no additional bore) to 427. And before I proceed any further, for those who are not familiar with the 63 427 engines, there were 2(TWO) distinctly different 427s in 63. The Z-11 (a W motor) was an RPO (believe it or not) and it was among the Mark I family (348-409-427). The other 427 was commonly referred to as the "427 Mystery engine". It was the Mark II engine. The Mark III was ONLY on paper. And as we all know today, the Mark IV (396-402-427-454) is now part of history! This engine WAS NOT an RPO, nor was it available to anyone through normal Chev channels. It was more or less a secret Chev engine dept engineering project. The exact number of Mark II 427s that were built (along with extra parts) will probably never be known. The bulk of the Mark II 427s of 1963 were made available in a rather clandestine manner to bonefide NASCAR types through channels such as Smokey Yunick. One of the better known cars to get a Mark II was the Holley Farms sponsored 63 Impala that was driven by Junior Johnson at the 63 Daytona 500. The small handfull of 63s with a 427 Mystery motor at Daytona literally blew away the competition. As soon as the idiots in upper GM management learned about this "Mystery 427", they had it killed immediately, sort of. It resurfaced in mid-65 as the well known 396. NOTHING, absolutely nothing from the 63 427 Mystery 427 will interchange with a Mark IV engine. Even though they "look" the same, they are not! Not even the heads have the same bolt pattern. I say nothing will interchange, that's wrong. The rear of the blocks still had the same bolt pattern (for the bell housing) and the bolt pattern on the crank for the flywheels are the same---------------and that's about it.
Now, back to the rest of the original Z-11 package. It consisted of a 1963 Impala 2dr hdtop---------------NOT AN SS. Plain, plain, plain. It had a 427 W motor with 2x4 carbs (AFBs) on a 2-piece alum manifold (it had a seperate baseplate kind of like a Rochester FI unit) and the FIRST cowl plenum air cleaner (it had a duct routed over to the right side of the firewall and took in outside air from the vents at the base of the windshield). The heads were different from the regular 409 heads (bolt pattern for intake manifold was different) and redesigned intake ports. ALL 63 Z-11s came with a 4sp and a posi with 30spline axles and axle gears (otherwise, the rearend center section was the same as 56-62 Vettes and 55-64 pass cars). EVERYTHING forward of the firewall was alum, including front-rear bumpers and bumper braces. No radio or heater. HD brakes (I've never had the opportunity to compare, but there was probably some interchangeability with the 63 Z06 brake components). This is the only way you could purchase a 63 Z-11 (except for color choices). Of course, this was NOT an advertised RPO, for understandable reasons. Again, no one knows the exact number of 63 Z-11s that were built and sold, but the number ranges from 47 to 57 units, with 57 being more commonly accepted (and that's disputed by some).

[Gary B.]

A question: Is it Z(zero)6 or Z(upper case O)6?

I notice that some of you posters use a zero for the middle character/digit and some use upper case letter O. Do we even know which of those two is correct?

Gary

[Robert Jorjorian]

Z06 with a zero is correct. *NM*

[Tom B.]

Re: Origin of "ZO6"

Thanks for the thorough explanation Tom. I remember the pictures in Hot Rod and the Cowl ducting has always stuck in my mind. Along with the Super Duty Pontiacs they were really amazing race cars.

Tom

[John H.]

Re: Origin of "ZO6"

The Z-11 '69 Camaro "Pace Car" package came first (all of which were produced prior to the Indy 500), then the dealers in the southwest zones who weren't allocated any howled about it, and the Z-10 "Paint Accents" package was released (well after the Indy 500) on coupes to placate the dealers who didn't get any of the real Z-11 cars. The Z-10 wasn't a complete SS vehicle package like the Z-11 Pace Car package was; Z-10 was only Hugger Orange Z-28 paint stripes on a white base coupe.

"Z" options had lots of interior and exterior trim and appearance applications in addition to the more well-known performance packages; for example, the '69 Camaro had these:

Z21 - Exterior Style Trim Group (bright moldings and pinstripes)
Z22 - Rally Sport Package (hidden headlights and moldings)
Z23 - Special Interior Group (woodgrain horn shroud and lower cluster insert, bright pedal trim, etc.)
Z27 - Actual RPO code for the "SS" package.
Z28 - Well-known performance package.
Z87 - Custom Interior (seats, door panels, woodgrain instrument panel, etc.)
ZJ7 - Rally Wheels, caps, and trim rings.
ZJ9 - Auxiliary Lighting package
ZL2 - Special Ducted Cold Air Hood