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Molon Labe
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I was reading Seniorsmokes lemon post, maybe someone could shed a light on something that I have wondered about but never gave it that much thought.

What do the letters stand for on Chevy car and pickup models, like the Z 28, LT1, and all the different ones on Corvettes
 

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When dealers order cars, there is an option sheet they fill out. GM uses alpha-numeric codes, and most of the performance options started with the letter Z.

Someone thought it would be cool to make decals to slap on vehicles like "Z71". It's just an ordering code.
 

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Designators such as Z28 and the like are RPO - Regular Production Option - codes. Every GM assembly component and option has one. C60 is manually-operated air conditioning, C65 is automatic climate control, Z71 (everyone is familiar with that one) is the off-road package for 4x4 pickups and SUVs and so forth. There really isn't any rhyme or reason to them except that many engine RPOs begin with L, climate control ones usually begin with C, emissions systems start with N, entertainment systems use U and rear axle codes often start with G. Back when GM offered two-tone paint on trucks, they also started with a Z - ZY1, ZY2, ZY3 and ZY4 with ZY1 being the simplest and ZY4 being the most elaborate paint scheme. Even tires carry an RPO that must be entered on the computerized order form when a vehicle is being ordered.

"Z28" was just the randomly assigned code for a package including a 302CID V8 with a four-speed Muncie close-ratio aluminum-cased gearbox, 15" wheels and a specific suspension package. Those transmissions were coded M20 (wide-ratio), M21 (close-ratio) and M22 (heavy-duty close-ratio). The Z28 package was created to allow the Camaro to complete in SCCA racing in that sanctioning body's Trans-Am class, where there was a 5.0L engine size limit. I forget the RPO code for it, but there was an "off-road package" for the 1969 Z28s that consisted of dual four-barrel Holley 650CFM carburetors on an aluminum cross-ram intake manifold, a higher-lift, longer-duration camshaft and tubular exhaust headers that was shipped in the trunk for dealer installation. A Z28 with that option, especially if it still is in its original packaging, is worth LOTS of money today as there were so few sold with it. Rear disc brakes were found on just 200 1969 Camaros and a folding rear seat was even more rare but the off-road package was the rarest. I'd bet that an off-road kit in its as-shipped packaging could fetch ten grand by itself and I could be way low.

Anyway, that's what those codes mean. Of course, then there were COPOs - COrporate Production Option codes for things like ZL-1 Camaros, Penske special-run orders and the like.

Ed
 

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Molon Labe
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Discussion Starter #4
Thanks all, I have just always wondered what they meant

Guess to a regular person they don't mean much
 

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If you hang around a GM dealership and watch new cars coming off the car carrier, you'll find a computer-generated sheet (or several) inside it that is the car's "build sheet" - the "instructions" so to speak for the assembly plant workers to know what color interior and what options that particular car gets as it travels down the assembly line. Every part is included - for example, even though it might indicate that a vehicle gets a heavy-duty suspension, every spring, spring mount, shock absorber, stabilizer bar and all the other suspension bits will be called out. The sheet consists of a maze of blocks, each with an RPO code in it for every item the vehicle gets.

Ed
 

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Ed - The "off road" package you described also came on the 1968 Camaro. A buddy of mine bought one in 1969, from an older gentleman who wanted a new sports car. He found it to be WAY too much to handle, and couldn't get anything for a tradein on a Corvette, so my buddy got it for $1900. The only difference between the '68 and '69 Z28s, as far as I can recall, was the '68 had Carter carbs.

The car was written off after an accident, due to a bent body and subframe, but John bought it back, got all new parts, and straightened the body using 2 big fir trees and some blocks and comealongs. It was built into a show car, and was sold for cheap when he needed to keep his business afloat. Last I saw of it, it was beat to he##, rat racing on weekends.
 

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like Ed said.,..the codes you mentioned were for extra special and super desireable suspension or engine drivetrain options...
for instance

L88..special high compression solid lifter 427ci big block
LS5- same as above but a 454
Z51- special sport suspension option on Vettes for really enthusiastic driving
ZL1- all aluminum all out racing 427
LT1- special hi performance 350 small block..the hottest one was a 350/370hp
LT5- special 350 Corvette engine ,..DOHC and 32valves..
L78- high performance 327ci..350hp in Chevelles and Novas...I had a 67 Nova SS with the L78 327/350hp..4spd , 4.10 rear..I changed the cam/ intake and carb and added headers with cutouts to uncap them for Friday nights..that little bugger would run mid 11 seconds..wish I had that one back :(
 

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GTO= Gran Turismo Omologato



noun<br>
1. (of an automobile) certified as conforming to the specifications, as fuel capacity and engine displacement, for a class of standard automobiles (Gran Turismo) qualified to engage in various types of competitions. Abbreviation: GTO
 

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While they weren't the fastest of the GM A-body muscle cars, I thought the 1970 Olds 4-4-2 with the W30 package was the most attractive. One of the real sleepers of that group was the '70 Buick GS with their Stage 1 package - "only" 360 rated horsepower but 512 lbs/ft of torque! Buick even had a very expensive dealer-installed Stage 2 kit for the Stage 1 455 engine but I never saw one.

Ed
 

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Ed

A friend ordered a new W-30 for 1970, and told them he wanted all the performance options.

When it came in, it was beautiful, Gold and Black, with Black interior, but......
he had wanted air cond., and it didn't have it, and it came with manual disc brakes.

I serviced the car in new, and I can tell you, you couldn't stop it in a football field.

They lied to him and told him that the performance he wanted only came with manual brakes, so he took it.

He sold it outright to an individual, who wanted to drag race it.

I was also racing in Ohio the day he raced. I saw him over by the river, carrying rocks to the car. He was putting them in the trunk for weight because he was frying the goodyears.

He made his first run, and ran clear off the end of the track because of the brakes.

He also sold it the next week, with a bent front fender.

A young customer brought in a 1970 GS-Stage I with the Muncie blown. It was showing 16,000 and some miles.

I pulled the trans and it was garbage, but I told the Service Manager the plastic gear in the speedo adapter was missing, and a short steel rod was in the hole.

When I put it back in, I put a new gear in, and made sure the speedo worked.

The boy blew up the 455, and we repaired it with all new moving parts, and it still had 16,000 miles.

Fast forward and the car has had about three owners, and in 1980, a City COp has it and wants me to work on it in my shop.

Yep, it still showed 16,000 miles and I told the cop the story.

Knowing this, he sold it to a guy from California and the advertisement said 16,000+ original miles.

Obey the Law!
 

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Calvin;

L78 was the RPO code for the 375 horsepower 396 with aluminum intake and solid lifters. Maybe you meant to type L79!

Steve Nunley

Albuquerque, NM
 

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All neat stuff. Average Ed, could it be argued that the A body muscle car Buicks put Kenne-Belle on the map as tuners? I believe that the Buick engine was way light for its cubes etc., an overlooked performance engine.
 

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Including my farm trucks and my classic, I own 4 Chevy trucks, 1 GMC Envoy Denali and a '66 Chevy Bel Air. Only Ford I ever owned was a '54 Victoria, my first car...

Ron Burr
 

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Average Ed,

My buddy has an all original red w/white top(hard top) 1970 Buick GS with the 455 sitting in his garage. I guess it's the Stage 1 model. It still has under 100,000 miles and while it is not his daily driver, he does drive it often. The paint has some sore spots, but there is no rust and it still runs like a champ. As you said, they were not the fastest kids on the block but it's still a 455 and it will sit you down and your seat and make you hold on. He is a die hard Buick guy.


It also has the white viynl interior. The guy who designed white interior obviously never had kids. LOL
 

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I thought the Z was for ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ..................Boring! Bankruptcy vehicles. Should give all tax payers a free one for a boat anchor. Beter than Japanese, but just barely.
 
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