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Bonneville Speed Week 2019: Alphabet Soup – What Do All Those Class Designation Letters Mean, Anyway?!

Bonneville Speed Week 2019: Alphabet Soup – What Do All Those Class Designation Letters Mean, Anyway?!

(Editor’s note: Starting this coming weekend, BangShift’s coverage of SpeedWeek 2019 will commence! As we are always gathering new readers we run this story about how to decipher Bonneville classes and rules to inform new land speed racing fans and refresh those who want to polish up their knowledge. Enjoy!)

 Knowing stuff is fun, right? Knowing stuff makes following any sort of event more interesting and engaging, especially when you are a gearhead and events like Speed Week have a lot of little intricacies to them and understanding those widgets makes all of this action make a ton more sense. One of the things that scares most people who have not spent a lot of time around the world of land speed racing or have poured over a rule book to decipher them are the sometimes lengthy class designations. Unlike the drag races where classes are usually about four letters long, you’ll see some pretty interesting letter combos on the salt with stuff like Xs, Vs, and even some that have letters and numbers. Once you get the hang of what this stuff stands for, you’ll gain a greater knowledge and appreciation of the performance numbers that the cars and trucks are putting up. Why? Because when you understand that something with an engine class break of K has a 30ci engine in it and it just went some ungodly speed, you’ll really catch salt fever. Make sense? Commence the lesson! (Editor’s note: As we’re a primarily car/truck based site, I am going to concentrate on the automotive designations and not the motorcycle stuff today. If I can get the time later in the week, I will include motorcycle stuff as well)


The first thing that appears in any Bonneville car class designation is a letter or a couple of letters telling us about the engine in the car. We’re going to run down the chart right here:

AA  = 501+ CID

A = 440-500.99 CID

B = 373-439.99 CID

C = 306.00-372.99 CID

D = 261.00-305.99 CID

E = 184.00-260.99 CID

F = 123.00-183.99 CID

G = 93.00-122.99 CID

H= 62.00-92.99 CID

I = 46.00-61.99 CID

J = 31.00-45.99 CID

K = 0-30.00 CID

Omega – engines that use a thermodyamic cycle other than Otto

So, if you jam a 580ci engine into your Camaro, you’ll be running in AA with respect to the engine. Now, it is important to note that these size designations have NO bearing in how you achieve that displacement. This is why you see guys running a V8 with one head on it or other bizarre methods to achieve the right displacement. Maybe a hemi with one head outflows even the gnarliest little 200ci four banger you can find so you need to make the most of that displacement allotment in your class by any means possible.

In addition to the traditional engine breakdowns you see here there are another set of class designations for vintage engines. In an effort to preserve history and keep a strong presence of hot rodding’s roots involved in land speed racing, the vintage classes take some of the classic obsolete engines from the past and group them together in an environment where they can be competitive. Here’s a rundown of those classes.

XF – Any production Ford/Mercury passenger car flathead V8 engine 1932-1953 measuring up to 325cid

XO – Inline overhead valve, inline flathead, and flathead V8 (outside of Ford/Mercury), and V12 passenger car/pickup truck engines. These are to be of 1959 or earlier design and displace no more than 325ci originally. The idea here is for engines like Chevys, Hudsons, Packards, Buicks, Lincolns, Cadillacs, etc to fill this class. Foreign engines are not allowed here.

XXF – See the same rules as XF above but adding a specialty cylinder head. The book defines that specialty head as one that is made from billet, cast, or is a modified OEM head that has added ports. At least one valve per cylinder must be in the head.

XXO – See the same rules as XF but with a specialty head (as described above) used on the engine.

V4 – This is the vintage four class and it is made up of any pre-1935 American made four cylinder engine up to 220ci. Specialty heads are allowed.

V4F – Flathead Vintage Four – Any pre-1935 originally designed and American made flathead four cylinder automotive engine up to 220ci. The engine has to have been produced as a valve in block engine and it must wear a flathead style cylinder head. Interestingly, the cam must remain in the block. (Honest to Pete, a dude showed up one year with a cam mounted OUTSIDE the block allowing him to run larger lift!)

OK, so there is your primer on the engine side of things. As I am not looking to recreate the entire rule book here, I want this to give you a loose idea of what you are looking at and encourage you to buy an SCTA rule book to really dive deep into the nuances of all this stuff.


The next thing you’ll see after the engine designation is a slash mark on the cars. (AA/….) We’re now going to talk about the stuff after that slash and the first thing we learn is about fuels and induction.

If the first letter you see after the slash is a G it means that the car is running on gasoline and nothing else. There is a single fuel supplier on the salt and that is where your gasoline needs to come from. If you are on gasoline you are running nothing else. No blower, no turbo, no nitrous, just straight up gasoline.

If the first letter you see after the slash is an F, it means that the car is running in a fuel category which opens the selections up to nitrous, alcohol, hydrogen, and everyone’s favorite, nitromethane. Outside of nitrous, it means that the car is running naturally aspirated on that particular fuel.

If the first letter your see after the slash is a D it means that the vehicle is running on diesel.

If the first letter you see after the slash is a B, it means that there’s forced induction involved as B stands for blown. This means belt driven centrifugal blowers, turbochargers, traditional roots blowers, etc. That B will be followed by a F or an G to determine whether the car or truck is running on gasoline or a more potent/exotic fuel.

If the first letter you see after the slash is an S it means that the vehicle is running on steam (seriously).

If the first letter you see after the slash is an E it means that the vehicle is running on electricity.

So as we are building our imaginary car here, we’re at: AA/BF   (“Double A/Blown Fuel…) — So we’re running a 580ci big block with a roots blower on alcohol


The rubber really meets the road at this part of the class designation because it is where you basically classify the car’s body. There are a HUGE number of classes at Speed Week and this thing would read like a telephone book if I were to just rattle them all off, so I am going to hit the most commonly seen classes out there and give you some basic idea of what they are.

Streamliner – These are the fastest cars on the salt and they are all-out efforts from the tiny engined entries to the 400+ MPH fire breathing monsters. Car needs four wheels in pretty much any configuration. Two of the four wheels need to be covered at minimum. Class designation is /S

Lakester – These cars have exposed wheels and range from the classic “belly tanks” to dragster looking creations. The bottom line is that the wheels and tires need to be fully exposed. Class designation is /L  (For instance Blown Gas Lakester = /BGL)

Turbine – Body configuration here is unlimited but if powered by a turbine, the car will have a /T at the end. There are three classes of turbine vehicles based on weight with III being the heaviest cars and typically the most powerful.

Modified Roadster – Must be an original or faithful reproduction roadster body ranging from 1923-1928 with any sort of frame and chassis under it. The engine can be relocated back in the car. To generally sum up the class, from the cowl forward virtually anything can be done but the wheels all need to be exposed. These look like classic roadsters that have been stretched out and given a nose job. Class designation is /MR  (example: Blown Gas Modified Roadster = /BGMR)

Rear Engine Modified Roadster – These are machines that must start with that 1923-1928 roadster body, the wheels must be exposed, but after that things get wild. The engine is obviously moved to the rear, wheelbases are stretched, wings are allowed, and these cars look little like a “regular roadster”. You’ll know one when you see one. Class designation is /RMR. (Blown Fuel Rear Engine Modified Roadster = /BFRMR)

Roadster – Body styles here range from 1928-1938 American made roadster body. These cars look like traditional roadster but hot rodded up. They can move the engine back in the car but they have to maintain the frontal grill area of a 1928 Ford. There is subtle conturing that can be done to the body, the windshield does not have to be stock sized, and tonneau covers are allowed. Think of a stripped and raced up hot rod and that’s a roadster class entry. Class designation is /R.

Street Roadster – The street roadster division is one of the most hotly contested on the salt and there are lots of killer cars in these classes. This is a highly restricted class in terms of body modifications. The body cannot be altered in height, width, or contour. Things like rear fenders are required, along with stock body panels, headlights, a horn, a transmission, a brake light, etc. These cars can run on gasoline only have have two classes. Blown street roadster and street roadster. /BSTR and /STR are the letter designations.

Competition Coupe and Sedan – This class allows for coupe and sedan bodied cars with bodies unaltered in width or contour to compete. Ahead of the cowl, the car can be stretched, streamlined, etc. The only actual major modification you can made from the cowl back is to chop the top.  Class designation here is /CC

Altered Coupe – This is a class made up of cars from 1982 to present unaltered in height, width, length, or contour. In order to fit into Altered you need 25% engine setback, a front wheel driver made into a RWD configuration, or most basically covered headlights and grille. These are very much “production” looking cars that have been modified but still retain a factory outward appearance. Class designation is /ALT.

Gas Coupe and Sedan – American and foreign cars that are largely stock appearing but have had an engine swap, use a quick change style rear end, or have a non-factory blower bolted to them make up the meat of this class. No streamlining, no use of headlight opening for induction, no narrowing bumpers, etc. Class designation is /GC

Modified Sports – Production sports cars that are heavily modified make up the Modified sports class. We’re talking lots of streamlining from the cowl forward, a chopped top (if there is a top), engine placement is optional, drive wheels can be on either end, any frame can be used, etc. There’s a car in this class shooting for 400 this year. Class designation is /MS.

Modified Mini Pickup Truck – 1972 and newer American and foreign small trucks. Must have a full stock bed, no body alterations, trucks must have an engine swap, non-stock blower, or quick change rear end to fit in this modified class. The bed can be covered with a tonneau or other means. Class designation is /MMP

Production – Just like it sounds, very few alterations allowed with the body, but you can go anywhere you want with the engine. These cars appear the closest to “factory” as almost anything you will see on the salt. Rear wheel drive conversions are NOT ALLOWED. Class designation is /PRO.

Production supercharged – See above but add a combo (Terminator Mustang, Grand National) that was delivered from the factory with forced induction. Class designation is /PS.

Grand Touring – This is a class for two seat sports cars under the Production umbrella. Honda S-2000, Chevy Corvette, Fiero, Miata, etc. They have stringent body modification regulations in this category as well. Class designation is /GT.

Production Pickup – Must be a gasoline burning engine, truck must be 1946 or newer, full stock bed and a virtually unaltered body. No forced induction, the bed can be covered and if the truck had a cab mounted tank it could be removed and relocated but not used for any aero advantage. Class designation is /PP.

Unlimited Diesel Truck – Just like it says, this is the fantasy land class where stuff gets crazy and awesome and the only real limitation is the fact that you need to run a diesel engine and meet all safety requirements for the speeds you are trying to run. One of our favorite classes for sure. Class designation is /UDT

Modified Diesel Truck – Diesel powered trucks with modified bodies. There are typically streamling mods made behind the cab in these trucks. No engine displacement breaks here, there is a single record no matter the combo as long as it is diesel powered. Class designation is /MDT.

Diesel Truck – Outside of the addition of an air damn, engine swaps, and the ability to pull wipers, mirrors, the antenna, and other small stuff, these trucks are largely factory appearing. Turbos and superchargers can be used on any truck without it causing some sort of class jump. Obviously diesel fuel has to be run. If the truck is older than 1948 a 3″ chop is allowed. Class designation is /DT.

Ok, now that we have seen some of the most populous classes on the salt and gotten a quick taste at what they are, we’ll throw one more wrinkle in and that is the Classic umbrella category that is a place for cars built between 1928 and 1981 to live. This means that if you are running Altered in your 1967 Camaro and you had a naturally aspirated 550ci engine on gasoline, your class designation would be: AA/CGALT (550ci engine/Classic Gas Altered). If the car was built after ’81 you’d lose the C. This is done because of modern aerodynamic designs render older cars at a huge disadvantage when running head to head for the same records in the same classes. Imagine a 1998 Camaro and a 1967 Camaro trying to run the same combo….which would be faster? Hmmmm.

Along the same line there is a Vintage umbrella category that gets applied as well. This takes 1948 and earlier cars with the vintage engines we talked about above (flathead fours, inliners, flathead V8s, etc) and moves them into their own categories. So if we were running a 1937 Cadillac with a blown, nitro burning engine in the Blown vintage fuel altered coupe category our designation would look like this: XXO/BVFALT (Vintage flathead engine/Blown Vintage body fuel altered coupe).

Now for a quiz!  If you have made it this far, decipher the five class designations below and put your answer in the comment section!














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2 thoughts on “Bonneville Speed Week 2019: Alphabet Soup – What Do All Those Class Designation Letters Mean, Anyway?!

  1. DanStokes

    A couple of additions (I’ve spent WAY too much time messin’ with LSR!).

    1) Buy and READ the rulebook before you decide to build a car. The smart money is to find a class that interests you, find a body with the smallest possible frontal area to start with, then build to the class. Too many folks build a car that floats their boat then try to force fit it into a class – that never works well.

    2) As I run in the DT classes it has given me some insight into how classes come to be. Brian’s description of the DT classes, for example, are spot-on but it’s useful to note that they’re based off the Gas classes for non-Diesel engine. Hence, there is no penalty for an engine swap just as there would be no penalty in Gas. You CAN run a stock Diesel in the body it came in but there’s no reason not to do a swap if you want to. This logic applies to some other classes a well – check with the class committee if there are any questions.


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