GM Engine Serial Number Lookup – What Do They Mean?

Knowing how to do a GM engine serial number lookup can be beneficial for you. It may not be so relevant for GM’s modern cars (like with the new crop of GM 1.5 turbo engine problems to worry about), but for the classic muscle car enthusiasts among you, there are benefits.

Of course, GM has made hundreds of engines over the years, such as the 283 Chevy engine, or the 400 small block, among many others. So, we’re going to focus on popular GM engines where we think it will be beneficial for you to learn how to do a GM engine serial number lookup. Here’s our table of contents to help you navigate:

• What Is A Serial Number?
• Chevy Inline-Six
• Pontiac V8
• Buick “Fireball” V8
• LS Engines
• FAQs

Engine Serial Number

The GM engine serial number is the production code of the engine. This production code will tell you the specifications of the engine. And in some cases, it will even tell you what year and where it was made. In other words, it’s an identification code for the engine.

The length and location of the code vary depending on the engine type. Additionally, the period when the engine was made also determines the code length and information. Older engines tend to have more complete information, while newer ones are more difficult to decipher unless you can find a complete database.

Since GM is a large automaker with a lot of brands under its wings, they’ve made hundreds of engines and we can’t possibly discuss them all. So, we’re focusing on four popular engines in this post: the Chevy inline-six cylinder, Buick’s “Fireball” V8, the Pontiac V8, and the LS engine family.

Wait, how about Chevy’s small-block and big-block V8s? Aren’t those popular GM engines as well? We already made an article for that, and you can learn how to lookup the Chevy engine serial number on those engines here. And fun fact, also check out our catalytic converter code lookup.

How To Tell What Engine I Have

Knowing this information has several benefits. For one, it will allow you to search for the correct parts for the engine. This takes out the guesswork of whether a replacement part will fit perfectly in your engine or not. Possibly saving you money in the process.

Another benefit is that sometimes there are problems specific to a certain model year of an engine. By knowing the engine’s production date, you can anticipate potential reliability issues. This allows you to make modifications to improve reliability in advance. Better to prevent than fix, no?

If you’re planning to do an engine swap, then knowing how to perform a GM engine serial number lookup will be useful. It will allow you to identify the specifications of the engine. Additionally, it’ll help you to seek information on whether or not the engine will fit in your cheap project car.

Sometimes, there doesn’t even have to be a benefit. Sometimes we just have a lot of free time and want to learn more about engine codes and specifications. While probably not the most effective ice-breaker during a first date, certainly useful to have this sort of knowledge at your next classic American muscle cars meet-up.

The bottom line is there are plenty of benefits. Maybe not so much in modern cars, but in older cars, identifying your engine’s serial number will be beneficial.

Engine Serial Number vs VIN

Is an engine serial number the same as a VIN? No, they’re different. VIN stands for Vehicle Identification Number, and it’s a 17-digit alphanumeric code. The VIN will tell you where the car was built, engine size, manufacturer, model year, and more.

In essence, it’s a unique chassis code designated for your specific car. Almost like a birth certificate, if you will. Meanwhile, as mentioned, the engine serial number tells you the production date and location of the engine. It contains useful information about the engine specs. But it doesn’t tell you much about the car that it’s in.

Also note that while the VIN format is the same across every manufacturer (except for carmakers that make less than 1,000 vehicles per year), the engine serial number format will be different from one manufacturer to another.

In most cases, knowing your VIN is more important. This is because not only does it allow you to search for information on all parts of a car to look for spares. But the VIN is necessary when you register and title the car or when you renew them. It will also come in handy should someone steal your car.

Although hopefully, that day will never come. The engine serial number isn’t necessary for those things. However, it is useful for maintenance and modification purposes. You can find your VIN in your vehicle registration numbers, or on the bottom of the windshield on the driver’s side. But how about finding that engine serial number?

Engine Serial Number Location

Unlike VIN, the engine serial numbers are usually not in your vehicle’s title number or registration (to learn more, check out our explainer on vehicle registration renewal WV). However, since every state has a different design for the title, some states may write the engine number on the title. One such example – if we’re not mistaken – is Kentucky.

If you can’t find it in your title, or you’re trying to find the serial number on an engine you’re planning to buy, then you’re going to have to take a closer look at the engine. As mentioned, we’re going to focus on four popular GM engines. We’ll take a look at the inline-six engines first:

GM Engine Serial Number Lookup: Chevy Inline-Six

First, a bit of history: the Chevy straight-six is an engine family made from 1929 to 1988 spanning three generations. There are a lot of variants, but we’ll focus on three: the 235, the 230, and the 250 since they’re the most popular.

The 235 is part of the second-generation family, most famously found in the original C1 Corvette from 1954 – 1957. As well as other cars such as Chevy 150, Chevy 210, and the Bel Air. Meanwhile, the 230 and 250 are part of the third-generation engine, most famously found in the first-generation Camaro.

Whether it’s the second or third generation, you can find the number on the passenger side of the engine block. Just a little behind the distributor. Here’s how to decipher the 235 inline-six engine:

Deciphering The Chevy 235 Inline-Six

The engine serial number consists of a prefix and a suffix. The prefix itself consists of: a six-digit unit number, plant code, and model year. Meanwhile, the suffix is either one or two letters that signify the vehicle designation.

The unit number starts with ‘1001’ at each plant and this number is for keeping track during manufacturing. The plant code doesn’t really matter either. This engine will have either an ‘F’ for Flint, Michigan. Or ‘T’ for Tonawanda, New York.

What you’ll want to pay attention to the most is the model year, so you know when it was made. And of course, the vehicle designation or suffix so you know what the engine was originally intended for. It will also give you information about the specs of the engine.

As an example, let’s use 0001001 F 54 YG. Let’s break it down:

• 0001001 is the unit number for the manufacturer to keep track of the engine during production.
• F is the code for the Flint, Michigan production plant.
• 54 means it’s a 1954 engine.
• YG means it’s a 235ci Corvette engine that comes with a Powerglide transmission.

This is an example of the 1954 model year. Throughout its lifetime, the engine uses this same code system. However, the suffix changes over the years.

For example, the suffix for the 1957 Corvette engines was either A, AD, or, B. The A engine has a three-speed manual, the AD means it comes with a heavy-duty clutch, and the B means it comes with the Powerglide transmission.

Once you find your 235 engine serial number, you can look it up on this website. It’s a community-driven guide led by Chevy enthusiast Keith Hardy. You’ll find a complete list of the engine codes and what they all mean.

Deciphering The Chevy 230 And 250 Inline-Six

As mentioned, the serial number for these engines also lies on the passenger side of the block just behind the distributor. However, the codes have a slightly different format than the second-generation engines and resemble that of the Chevy small and big block V8s.

The code’s prefix consists of the plant code and production date. While the suffix is a two-letter code that tells you the engine application. As an example, let’s use F1012 LH. Let’s decipher them:

• F is the plant code for Flint, Michigan. This is the only plant where the inline-six was produced.
• 1012 is the production date. This means the engine was made on October 12th.
• LH is the engine application. In this case, LH means it was a 1967 230ci base inline-six producing 140 horsepower. This particular code means the car came with a smog pump, air-conditioning, and the standard automatic transmission.

The suffix also tells you what year the engine was made since every year it had a different suffix. For example, LH is a 1967 engine, while the 1968 version of the engine with the same specifications will have a ‘BH’ suffix. Once you find the engine serial number, you can look it up on this database.

GM Engine Serial Number Lookup: Pontiac V8

The Pontiac V8 engine family was made from 1955 to 1981. You’ll find this engine in many popular Pontiacs such as the GTO, the Firebird, and the LeMans amongst others. The engine size ranges from 265ci (4.3L) to 455 (7.5L).

Despite being under the same wings of GM as Chevy, Pontiac uses a different format for its engine codes. They usually have a date code, a casting number, and an application code. To add to the confusion, the date codes can overlap up to three decades.

Additionally, the date code and casting number may be in different locations. The only blessing is that the locations are usually the same regardless of the engine size.

For the casting number and date code, you’ll find them on the back of the block, just underneath the distributor. Meanwhile, you’ll find the application code at the front of the block on the passenger’s side. Usually a little bit above the water pump.

The casting number serves the same purpose as the unit number in Chevy’s inline-six engines. It’s an internal code to keep track of the engine during production.

Meanwhile, the date code will tell you when the engine was made. But as mentioned, this code can overlap up to three decades. So, you’re going to have to cross-reference it with the casting number and application code. Bottom line: it’s more confusing than Chevy’s system.

Deciphering The Pontiac V8

You won’t be able to decipher the casting number as they’re just a sequential number used internally. What you can decipher are the date and application codes. The date code consists of a letter and a three-digit number. Meanwhile, the application code is a two-letter code but is sometimes alphanumeric. And this code will tell you the size and application of the engine.

As an example, let’s take A249 XE:

• A is the month code which is January. They use the alphabet to signify the production month. So, A is January, B is February, and so on through L as December. Note that – for unknown reasons – the month code for December in 1967 was M.
• 24 refers to the production day, in this case, it was the 24th.
• 9 refers to the last digit of the year it was made. It can either be ’59, ’69, or ’79. See how it can be confusing? You’ll need to cross-reference this with the application code.
• XE is the engine size and application code. You’ll need to look it up in a database, but in this case, XE means it’s a ’69 428 engine.

Another example as shown in the video above is A209 YD. This means the engine was made on January 20th. Cross-reference the year code and application code, and you’ll find it’s a ’69 400ci engine.

After you’ve found your engine’s date and application code, you can look for it on this database. Find your application code, and then cross-reference it with the date code. It’ll tell you the engine size, the original transmission, and the application.

GM Engine Serial Number Lookup: Buick “Fireball” V8

The popularity of the Chevy V8s probably overshadows this engine. But it was a popular engine and still has a following to this day. Also known as the “Nailhead”, you’ll find this engine in many popular GM cars, such as the ’60s Buick LeSabre, Buick Wildcat, and even the Pontiac LeMans.

Now, this engine has a lot of variants and was in production for 28 years. Throughout its production, the location slightly changes depending on the year and engine type. So, this might get a little confusing but we’ll try to make it as simple as possible:

• 1953 – 1956 264 and 322 engines: on top of the driver’s side of the cylinder bank. Somewhere between the middle branches of the exhaust manifold.
• 1957 – 1966 364, 401, and 425 engines: on the passenger’s side of the engine block, just in front of the valley pan.
• 1961 – 1963 215 engines: on the front of the cylinder head of the passenger’s side.
• 1964 – 1966 V8 & 1966 V8 340 engines: the engine serial number is on the driver’s side of the front face of the crankcase. While the production code is on the passenger’s side of the crankcase between the middle branches of the exhaust manifold. It will be necessary to remove the power steering pump (akin to a replacement) back to view it in cars with power steering.
• 350, 400, and 430 V8s: the engine production code number is between the two forward branches of the right exhaust manifold, and the engine serial number is between the two rear branches.
• 455 Big-Block V8s: the production code is between the two front plugs and the exhaust manifold on the driver’s side. While the serial number is below the deck.

Deciphering The Buick “Fireball” V8

You may have noticed that we mentioned a production code and a serial number. The serial number is an eight-digit code, while the production code is a five-digit code.

Unfortunately, not much information can be found regarding how to decode the serial number. From what we can work out, the serial number is a partial VIN, but there is no solid information on how to decode them. All we know is that the last six digits are the sequential production number.

Meanwhile, the production code has five digits; the first two are either letters or an alphanumeric code, and this will tell you the engine size and production date. For example, the ‘PD’ date means it’s the 430ci engine from 1968. However, we aren’t able to find any information either on what the last three digits mean.

Information on Buick’s engine codes is rather limited compared to the other engines we’ve discussed so far. However, finding the first two digits of the production code should be enough to help you identify the engine.

Once you find the code, you can look it up on TeamBuick. They have a lot of other useful information as well regarding old Buick cars and should serve as a good guide if you’re working on a Buick project. And, maybe think about comparing a long block vs a short block engine.

GM Engine Serial Number Lookup: GM LS Engine

Finally, we get to the ever-so-popular LS series engines. The LS is the continuation of the Chevy small-block V8s, made from 1997 until today. Most famously found in the modern-age Corvettes, but there are LS variants where it’s used for trucks such as the LY6 engine.

The purpose of knowing how to do a GM engine serial number lookup is to identify the engine’s specifications. When it comes to LS engines though, the method of identifying them is slightly different from the other engines we’ve talked about so far.

Identifying By VIN

If you’re buying a vehicle that was factory-equipped with an LS engine, then you can easily identify what type of LS engine it has by looking at the VIN. Specifically, take a look at the 8th digit of the VIN.

Note that the code may overlap. For example, a ‘G’ signifies that it has a 5.7L LS1 engine. However, it may also mean it’s a 6.0L L96 Vortec 6000 engine (and if you own one, be wary of the Chevy 6.0 engine problems). The key thing here is to know what type of car you’re looking at.

If it’s a GM truck, such as the Silverado 2500 HD, then it’s the L96 variant of the engine. If it’s a sports car like the Corvette or Camaro, then it’s the 5.7L LS1 engine. You can take a look at Summit Racing to help you find out. There’s a complete list of what the VIN code means and its applications.

Of course, if you know the VIN, then you don’t need to know the engine serial number. This is because when you’re looking for replacement parts, you can often enter the VIN of the vehicle and you’ll find the exact parts that you need.

If you’re buying a junkyard engine or don’t have the VIN, you’re going to have to take a closer look at the engine. And this is where it gets a bit tricky:

Inspecting The Engine

LS engines have a casting number and a date code on the engine block. The engine block casting number is an 8-digit numerical code on the back of the engine on the passenger side. The problem is that this number only serves as an internal code for GM to keep track of production.

If you’re lucky, you can Google this casting number and it may return results telling you what type of engine this casting number is for. For example, the casting number ‘12578181’ will return results for the 5.7L LS1 engine.

The cylinder heads also have a casting number, this is because the heads are often interchangeable between LS engines. For example, the LS7 cylinder head casting number is 452. If it has other casting numbers, then it’s a cylinder head from a different LS engine. You can view the complete list of cylinder head numbers here.

However, this doesn’t tell you the production date of the engine. Unfortunately, you’re going to have to take off the cylinder heads (handy if you’re already tallying the cost of a cylinder head replacement) to find the production date. It’s usually on the rear top of the engine block on the driver’s side, and it’s a four-digit alphanumeric code.

The production date code would be something like C246. The C signifies the production month. Since C is the third alphabet, this means the engine was made in March. The next two digits are the date, in this case, it’s the 24th. And the last digit is the production year, in this case, it means 2006.

Chevy Small Block V8 Engine Identification Facts

1. When decoding a Chevy small block V8 engine, the primary pieces of information to decode are the engine code and partial VIN, casting date, and casting number.
2. “Numbers matching” means the engine can be matched to the vehicle it was originally used in via the partial VIN stamp on the component.
3. Numbers matching is important for decoding a Z28 or Super Sport, where the VIN won’t identify the vehicle as such.
4. To verify if the numbers stamped onto the component were the ones stamped into it originally, you may want to verify that they aren’t restamped.
5. The engine ID code consists of an assembly plant code, production date, and suffix code, with V8 codes stamped on a pad just forward of the right side cylinder head.
6. The VIN code format is stamped onto most engines and consists of divisional identification number, model year, assembly plant designation, and vehicle serial or sequence number.
7. In 68-69 model cars, the serial (VIN) number of the car the engine was installed in is stamped next to or under the engine code ID.
8. The small block casting date is located on the driver-side rear of the block on the flange forward of the bellhousing, while the big block is on the right side of the engine above the oil pan rails.
9. The engine block casting number provides information such as CID, low power, high power, and main caps, among others.
10. Four-bolt main blocks are desirable in high-performance applications because the extra strength of the additional bolts keeps the bottom end rigid and less prone to failure.

FAQs On GM Engine Serial Number Lookup

There you go, that about covers it on how to find the serial number on some of GM’s most popular engines. Hopefully, this has been a helpful guide for you! And if you’re still curious to learn more about GM engine serial number lookup, our FAQs here might help…

How To Read Chevy VIN Numbers

To read your Chevy’s VIN numbers, you’ll first have to figure out where it’s stamped on. You can find these in your car’s title or registration. Otherwise, the VIN is found on the dash (under the windshield), or by the firewall or door jamb. Once you’ve found that 17-digit VIN, you can then decode it. The 1st and 2nd digits will say who built your vehicle, whereas the 3rd digit will show which specific division put it together. Meanwhile, the 4th digit is telling you the GVWR, the 5th digit for the chassis type, and the 6th digit for its classification. The 7th digit tells you the body type, the 8th digit for the engine code, the 9th a check digit, the 10th for the year, and the 11th for the plant location. The final 6 digits are for the production sequence.

How To Find Engine Size On Engine Block

You can find out your engine size by locating one of two codes – the engine serial number, and the block casting number. To locate the engine serial number, you’ll have to look near your alternator, water pump, or on the block itself, which is printed on a metal plate. Or, if you need to find the block casting number, this usually involves you needing to lift your car up, and locate it between the engine and transmission. Using both the engine serial number and block casting number, you can then use online resources (such as the decoding guide we have up there) to cross-reference the codes and figure out your engine size, as well as other miscellaneous details.

What Is A Small Block Engine

When it comes to classical engines from GM brands such as Chevy, it’s usually split into two types – small-block engines, and big-block engines. So, what’s the difference, and what is a small block engine? Well, a small-block motor is physically smaller than a big-block – hence, its name. With a smaller footprint, small-block engines have a smaller bore and shorter stroke. They also have smaller displacements, by comparison. Yet, these small-block engines are lighter, which translates to better handling and acceleration. That compensates well for its downsizing, in addition to better fuel economy (and just as much tuning potential) compared to a big-block engine.

Are All Chevy 350 Blocks The Same

Among the most ubiquitous powerplants of its era, Chevy’s 350 V8 motor is still around with us today, mainly as crate engines. With such a long production run then, is every Chevy 350 block the same, even between the new crate engines and classic examples? For the most part, this is true, they are the same. Nevertheless, certain 350s might not be able to interface with other 350s as seamlessly, despite (nearly) matching sensor mounts, head bolt patterns, and so on. For example, older 350 blocks use mechanical pumps or lack fitments for knock sensors and crankshaft sensors, in addition to using a different rear main seal design compared to later 350s motors.

How To Identify A 6.0 LS Motor

Chevy and GM’s LS engines are one of the most diverse families of engines around. With more than 40 distinct variations, it can be tough to discern from one LS to another. Yet, there are ways to identify them. The easiest technique that you can try is by checking the VIN number. Specifically, look at the 8th digit of your VIN, which tells you the engine code. If you’re looking for a 6.0 LS (Gen 3 Vortec), look for the letters U and N in the 8th digit. Meanwhile, 6.0 LS (Gen 4) could be noted by the letters U, Y, and 2. If you have a Gen 4 Vortec, then a 6.0 LS can be identified by the letters K, G, H, Y, 5, and J, instead.

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