Home Cars 20 Muscle Car Codes and Terms You Should Know

20 Muscle Car Codes and Terms You Should Know

Vukasin Herbez November 11, 2018

If you ever heard the dialogue between two full-fledged muscle car fans, you may have noticed they were talking in a secret language full of strange codes and numbers. It probably sounded like a military-type conversation where every letter and number meant something. And, in fact, it does. In the colorful world of muscle cars, engine codes, trim designations, model names and factory markings mean a lot.

And even in some cases, just two letters can make a world of difference to a knowledgeable muscle car expert. However, if you don’t know any of them, fear not. Here are the 20 most common and popular muscle car codes and terms. So, read this muscle car glossary to help you understand those terms better, so you can communicate with fellow car enthusiasts.

Soon, you’ll be able to spread the word about these glorious monster machines. So here are the top 20 of them in simple alphabetical order.

  1. The AAR: A Tribute to All American Racers

The 1970 AAR Plymouth ‘Cuda was a limited production model they built to commemorate Dan Gurney’s All American Racers team. That is because they used ‘Cudas to compete in the Trans Am championships. It came with a 340 V8 small block and special plastic hood in matte black paint.

It also had a hood scoop, rear spoiler and interesting side graphics that included a big AAR logo. This version was somewhat more expensive than the regular 340 ‘Cuda. And that’s why they only made 2,724 of them.

  1. Big Block V8: All About Size and Displacement

People commonly use this term for engines that are large in both size and displacement. Also, they often were a top of the line option for muscle cars. Most commonly, they use the big block term for those Chevrolet or GM powerplants with displacement at or above 400 cubic inches. However, the big block also designates the specific engine architecture.

In fact, the big block V-8 different from the camshaft in block type they often use on small block engines. But the main feature is the eight-cylinder V-shaped configuration with the cylinders sitting on the crankcase in two sets of four pistons. For the ultimate power, all eight of the pistons drive a common crankshaft.

  1. The Boss: Limited Production Beasts

Car fans often use the term, “The Boss,” to describe Ford’s limited production Mustangs. They came in the form of the Boss 302, the Boss 429 and the rare Boss 351. Those models featured numerous special items like high-performance engines, special trims and exterior details.

The Boss 302 and 429 were practically homologation specials, first for the Trans Am championship and later for the NASCAR oval. But the rarest is the Boss 351 which Ford only introduced for one year, in 1971. It was a high revving street fighter that collectors still prize today.


  1. The C6: A Ford Gearbox

The C6 is Ford`s code for their heavy-duty automatic gearbox which they introduced in 1966. They often used this transmission on those powerful FoMoCo muscle cars, as well as on some trucks and the Bronco off-roader. The official name was the Cruise-O-Matic transmission.

  1. COPO: On Special Order

COPO is short for “Central Office Production Order.” It was the Chevrolet department for fleet buyers and special-order vehicles. In fact, most muscle car tuners like Baldwin Motion, Yenko, and Fred Gibb Chevrolet ordered their Camaros and ZL1 models through this department. A COPO is often a barebones car with a 427 or 454 engine, which wasn’t available in regular cars.

  1. The Detroit Locker: A Bullet-Proof Design

The Ford 100-percent automatic locking differential was an option on various models with steep differential ratios. This system offered the highest level of traction for street/drag racing. So, to properly launch the car off the line, you’d need a locking differential. The Detroit Locker was one of the best in the business, keeping all the wheels in drive mode, even when one wheel came off the road.

  1. DOHC/OHC: Valve Train Construction

DOHC stands for, “Double Overhead Camshaft,” while OHC means, “Overhead Camshaft.” Both are simple terms describing the construction of the valve train. The double overhead camshaft is not a standard of the industry. In fact, they were rare in the classic muscle car days.

Most engines had a single overhead camshaft or camshaft in the engine block like the famous small-block Chevrolet V8. However, some manufacturers experimented with DOHC layouts for added performance and revving capacity.

  1. Dual Quad: The More Barrels, the Better

To feed the engine with as much air as possible, engineers mount multiple carburetors to create some interesting combinations. And one of the most popular that also provides much power is the dual quad. The dual qual intake system consists of two four-barrel carburetors. And that means you get eight barrels to feed your engine.

  1. Four-Bolt Main: Designed for High Revving

In engine construction, the crankshaft`s main bearing cap connects with two bolts to the engine block. However, if you want more performance, the crankshaft has to endure much more torture, especially at high RPMs, so two bolts are not enough. So, that’s why engines they designed for high revving and maximum performance have a four-bolt main bearing cap.

  1. Glasspack: More Noise Means More Fun

Even today, you can buy those inexpensive yet popular low-restriction mufflers for an aftermarket installation in your car. They were famous for their fiberglass packing; hence, the name, as well as for minimal noise isolation. In other words, cars fitted with a Glasspack were extremely noisy and fun.

  1. The HEMI: An Infamous Engine

The secret of the Hemi engine is in its cylinder heads that have hemispherical combustion chambers; thus, the name. Although such a solution wasn’t new or unique in the car industry, Chrysler perfected it, making a brand out of it. They presented the street version of the mighty 426 Hemi in 1966. It featured a four-barrel carburetor and a lower 10.5:1 compression ratio.

However, it had the same basic block and heads as the race variant. The factory rated the 426 Hemi at 425 HP, yet it was clear that the engine produced more than that. Most historians agree the real output of the 1966 to 1971 street Hemi was over 500 HP. The Hemi package was available on selected Dodge and Plymouth models.

But it was expensive at $900 to $1,200, which was around a third of the price of the car. The Hemi was an expensive option since the production of the engine cost more. Also, such power required a heavy-duty suspension, frame and gearbox as mandatory options.

  1. The Muncie M22 Rock Crusher: A Heavy Duty Monster

Muncie is the brand name of a series of manual transmissions common in GM muscle cars. There are three basic types. The M20 is a wide ratio manual and the M21 is a close ratio manual. However, the M22 is a heavy-duty close ratio manual transmission people often call the “Rock Crusher.” As you probably guessed, the M22 is the most desirable if you own a Camaro, Corvette, Mustang or any muscle car.

  1. The Magnum 500: Made for Muscle Cars

One of the most popular wheel choices in the muscle car era were those beautiful Magnum 500 wheels they introduced in late 1963. First available in the 14-inch size, they later became available in 16 inches, since the dimensions of wheels grew. The Magnum 500 was a rather common factory option on almost all models of muscle cars.

In fact, Ford, GM and Mopar all used them on their cars. Interestingly, only one company refused to install them on their muscle cars. No Pontiac ever came with Magnum 500 wheels. They used their own version they called Rally II wheels.

  1. N.O.S. or New Old Stock: Never Used

N.O.S stands for “New Old Stock,” which describes a part or component they produced back in the day, but never used. N.O.S. parts are still in their original packaging and they never opened or messed with them. Collectors are willing to pay top prices for such items since they deliver more originality to their restorations.

Beware, though, because some N.O.S. parts like rubber hoses or weather-stripping kits are not safe to use since the materials have probably deteriorated over time. In some cases, you want newer parts for your restomod.

  1. Numbers Matching: Like They Just Left the Factory

Numbers matching means that the car has an engine, gearbox, production and drivetrain code that is the same as the Vehicle Identification Number (VIN). Numbers matching cars are as original as the day they left the factory assembly line. For that reason, they will always command higher prices than cars that they have replaced or modernized the drivetrain.

  1. Ram Air: Feeding Fresh Air to the Engine

Ram Air marks the induction systems characterized by the openings on a car’s hood, grille or even below the bumpers in some Oldsmobile models. They are designed to feed fresh air to the engine. Almost all muscle car manufacturers produce some kind of Ram Air device. However, Pontiac was the most famous for naming its system “Ram Air,” marketing it as a special performance package on their GTO and Trans Am models.

  1. Restomod: Modernizing Old Cars

Restomod stands for restoration and modification. It describes when drivers restore their classic cars to perfection. Restomod means the addition of modern engines, transmissions, suspension parts, safety upgrades and creature comforts. During that process, they remove all the flaws.

The new creation is a thoroughly modern machine that performs better, yet it still retains its classic style and looks. This is a common choice among most classic muscle car owners. Restomod helps modernize old cars and brings them to the performance and handling levels of modern machines.

  1. The Shaker: When Hood Scoops Rock N’ Roll

The Shaker is a hood scoop they mount on top of the car intake system. Visually, it sticks through the hood. Since it is an integral part of the engine, the hood scoop moves and shakes as the engine works; hence, the name. Most popular shakers were on Dodge and Plymouth cars, but almost all other muscle car brands have at least one model with this feature.

  1. SS: Super Sport or Super Stock?

The double S stands for “Super Sport.” It has been Chevrolet’s prime designation for performance models since 1961. Over the years, Chevrolet produced the Impala SS, Camaro SS, Nova SS and Chevelle SS, among others. They were even close to introducing the Corvette SS. But sometimes, SS can stand for “Super Stock,” which was a popular drag racing class back in the day for stock and factory models.

  1. The Z/28: Nimble Handling and a Thrilling Performance

The Z/28 has been a production option for numerous Camaro models since 1967. It was always the lighter, nimbler version of the SS model. The first Z/28 package included front disc brakes, a close-ratio four-speed manual transmission and a revised suspension and steering. It also came with exterior trim details like racing stripes and a vinyl roof and headlight covers.

But the real treat was under the hood. The power came from a 5.0-liter V8 engine delivering 290 HP, creating its high revving nature. This engine proved to be ideal for the Z/28. In fact, it gave the car its thrilling performance while retaining the low weight to offer, exciting yet nimble handling.

This has been a vehicular vocabulary with the 20 muscle car codes and terms you should know. The next time you hear two muscle car fanatics discussing the Boss or dual quads, you’ll be able to follow right along with them. And best of all, if you’re in the market for a classic or modern muscle machine, you’ll have a better chance of getting the best one for your buck.

Please wait 5 sec.