GM Engine Serial Number Lookup

How To Decode & Lookup A GM Engine Serial & Casting Number?

If you need to know more about an engine’s details or past, knowing how to do a GM engine serial number lookup can be beneficial. It may not be so relevant for GM’s modern cars, but for the classic muscle car enthusiasts among you, it could help with repairs or restoration work, when you know how to decode an engine serial number and block casting code.

Of course, GM has made hundreds of engines over the years, such as the 283 Chevy engine, or the 400 small block, among others. So, for now, we’re going to focus on some of the more popular ones to understand how to do a GM engine serial number lookup. For Chevrolet engines, we’ve also done a separate guide specific to how to lookup a Chevy engine serial number.

What Is An 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 was its model year and where it was made. Not to mention, highlighting its specs, or what car it was made for. In other words, it’s an identification code for the engine.

The length and location (usually on the engine block or cylinder head) 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. But, we’ll also include a few more here as we continually expand this list.

1. Chevy 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 has changed 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.

How To Decode A Chevy Inline-Six Engine Serial Number

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.

2. Pontiac V8

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.

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 is 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.

How To Decode A Pontiac V8 Engine Serial Number

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.
  • 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 would be something like 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.

3. Buick “Fireball” V8

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.

How To Decode A Buick “Fireball” V8 Engine Serial Number

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.

4. GM LS Engine

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, to do a GM engine serial number lookup, 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:

How To Decode A GM LS Engine Serial Number

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.

5. Chevy Small-Block V8 (SBC)

GM Engine Serial Number Lookup

The engine serial number for the SBC is usually found on a flat pad in front of the passenger-side cylinder head. It typically starts with the engine assembly date followed by the suffix code. The engine assembly date is a combination of the month as a letter (A=January, B=February, and so on), followed by the day and year. For example, A18 means January 18th.

Following the date, the suffix code helps identify the engine. For instance, let’s analyze V0403HR. Here’s the breakdown:

  • V stands for Flint, Michigan, where the engine was manufactured.
  • 0403 represents the assembly date, i.e., April 3rd.
  • HR identifies the engine type. In this case, HR signifies a 1958 283ci V8 with 185hp.

How To Decode A Chevy Small-Block V8 (SBC) Engine Serial Number

Thus, if your engine’s serial number reads V0403HR, it means it’s a 1958 283ci V8 manufactured on April 3rd in Flint, Michigan.

Over the years, different suffixes have been used. Some more examples:

  • FA: 1957 265ci V8 with 162hp.
  • GD: 1962 283ci V8 with 170hp.

Each suffix gives you a snapshot of the engine’s year of manufacture, its displacement, and its horsepower. To ensure you have the most accurate details, cross-reference with reliable Chevy databases or communities, such as or maybe at They have resources that list the hundreds of suffix codes and their meanings for the Chevy Small-Block V8.

Transitioning to the Small-Block V8’s later models, the coding system has remained remarkably consistent. This not only facilitates the decoding process but also highlights the lineage and evolution of the engine. Such a structured and systematic approach has allowed enthusiasts and professionals alike to trace the origins of their Chevy Small-Block V8s with ease.

6. Chevy Big-Block V8 (BBC)

If you’re attempting to decode a BBC’s serial number, start by locating it. Typically, it’s stamped on a pad on the front passenger side of the engine block, just below the cylinder head. This should make trying to do a GM engine serial number lookup much easier.

Once you have the serial number, the decoding process is somewhat similar to the Small-Block. The code usually begins with the assembly date, represented by a combination of a letter for the month (A for January, B for February, etc.), followed by the day and year.

Post the date, the suffix code aids in pinpointing the engine’s specifics. To illustrate, let’s dissect T0105IV:

  • T represents the Tonawanda plant.
  • 0105 indicates the engine was assembled on January 5th.
  • IV identifies the engine variant. In this context, IV indicates a 1972 402ci V8 with 240hp, intended for a Chevelle with a Turbo-Hydramatic transmission.

Several other suffixes exist:

  • JE: 1969 427ci V8, 430hp, used in the Corvette.
  • CRX: 1965 396ci V8, 375hp, found in the Impala.

To decode these, refer to some of the resources, registries, and links we mentioned earlier, up above.

7. Chevy 90° V6

For those on the hunt for the Chevy 90° V6’s serial number and wanting to do a GM engine serial number lookup, look on a flat pad at the front passenger side of the engine block, near the water pump. This location is consistent with its V8 relatives, a testament to its derivative nature.

The coding system mirrors that of its V8 cousins, making the decoding process familiar. It starts with the engine assembly date, marked by a letter denoting the month (A=January, B=February, and so on), succeeded by the day and year.

The suffix code, appearing after the date, reveals specifics about the engine. As an example, let’s explore F0723ZDR:

  • F signifies the Flint, Michigan plant.
  • 0723 represents July 23rd as the assembly date.
  • ZDR points to a 4.3L V6 from the late ’80s, equipped with throttle body fuel injection and designed for a passenger car.

Diving deeper into suffixes, here are some more for context:

  • ZDA: Early ’80s 229ci V6 with a 2-barrel carburetor.
  • ZDM: Mid-’80s 4.3L V6 with throttle body fuel injection, suited for trucks.

Once again, the databases and registries that we linked to earlier may point you toward how to properly decode these.

8. Northstar V8

If you’re looking to uncover the secrets behind the Northstar V8’s serial number, direct your gaze toward the rear of the engine, close to the transmission bell housing. Here, to do a GM engine serial number lookup, look out for it on a flat pad, and you’ll find the engine’s unique identifier.

Diving into the Northstar V8’s serial number offers a gateway to its rich heritage. The code usually kicks off with a letter denoting the assembly plant, followed by the production year, and then a string that stands for the day of the year.

Let’s decode a hypothetical number: Y2990154:

  • Y represents the Orion Assembly plant in Michigan.
  • 299 indicates the engine was produced on the 299th day of the year.
  • 0154 is a unique sequence number for the engine on that particular day.

To provide clarity, suffixes are often used in conjunction with these codes, representing engine specifics:

  • 9Y: Denotes a 4.6L V8 with 275 hp, commonly found in several Cadillac models.
  • 9S: Suggests a 4.6L V8, but with a higher output of 300 hp, often paired with the Cadillac STS and DTS.

Check out those links from earlier to find out how you can decode these.

9. Oldsmobile Rocket V8

The adventure of discovering the Rocket V8’s serial number starts at the left side of the engine block, just above the oil pan rail. This placement made it relatively straightforward for car aficionados and mechanics to spot and to do a GM engine serial number lookup.

The Rocket’s serial number provides a window into its genesis. The coding typically begins with the production year, followed by a letter indicating the assembly plant, and concludes with a unique engine sequence number.

For illustrative purposes, let’s decode a sample number: 57K100001:

  • 57 signifies the production year, 1957.
  • K stands for the Lansing, Michigan plant where Oldsmobile was headquartered.
  • 100001 is the unique sequence number for that specific engine.

Adding a layer of depth, suffix codes were used to provide details on engine specifications:

  • D88: A suffix hinting at a high-compression, 371 cubic inch V8 from the late 50s.
  • E80: Indicating a 394 cubic inch V8, often reserved for high-performance applications in the early 60s.

To decode this, check out those links we mentioned earlier, as well.

10. Oldsmobile Diesel V8

To find the serial number on an Oldsmobile Diesel V8 and do a GM engine serial number lookup, cast your eyes to the driver’s side of the engine block, right near the front, where it meets the cylinder head. The number is typically stamped on a flat section, ensuring relatively easy visibility.

Unlocking the mysteries of the Diesel V8’s serial number reveals its lineage. The code generally starts with the year of production, then a letter indicating its assembly location, and finally, a specific engine sequence number.

Let’s navigate a typical number: 82L123456:

  • 82 denotes its production year, 1982.
  • L symbolizes the Lansing, Michigan facility.
  • 123456 represents the unique sequence number, indicating its manufacturing order.

Suffix codes accompanying these sequences provided further insights into engine specifications:

  • LF9: This suffix denotes a 350 cubic inch (5.7L) diesel V8, one of the most prominent in the lineup.

Decoding the engine serial number can be done by checking out the links we mentioned up above.

11. Buick V6

Your quest for the Buick V6’s serial number will lead you to the driver’s side of the engine block, typically right behind the cylinder head or close to where the engine mates with the transmission. Due to its consistent placement, spotting the serial number is usually a straightforward endeavor, which makes trying to do a GM engine serial number lookup easier.

Diving into the details of the Buick V6’s serial number, you’ll typically encounter the production year first, followed by a letter symbolizing the assembly plant, and concluding with a unique engine sequence number.

An illustrative breakdown using 79B567890:

  • 79 indicates the production year, 1979.
  • B stands for the Flint, Michigan assembly plant.
  • 567890 is the specific sequence number, denoting its manufacturing sequence.

Furthermore, suffix codes on these engines give more granularity on engine specifics:

  • LD5: Refers to a naturally aspirated 3.8L V6.
  • LC2: Indicates a turbocharged 3.8L V6, commonly associated with the high-performance Grand National.

Once again, to decode what these sequences mean, check out those databases we mentioned earlier.

12. Cadillac HT4100

To unearth the serial number on the Cadillac HT4100 and perform a GM engine serial number lookup, venture to the driver’s side at the front of the engine block. Here, the number is typically stamped, offering clear visibility to those keen on decoding its secrets.

Dissecting the HT4100’s serial number, you’re likely to first come across the year of production, then a designated letter for its assembly plant, and finally, an engine sequence number unique to each unit.

Using 83C234567 as an example:

  • 83 reveals its production year, 1983.
  • C represents the Detroit, Michigan assembly plant.
  • 234567, the sequence number, signifies its unique manufacturing order.

Engine suffixes provide a deeper dive:

  • 8: This denotes the HT4100, clearly marking the engine’s lineage.

Decoding this ought to be a lot easier if you refer to those registries we mentioned earlier.

13. Quad 4

To locate the serial number on the Quad 4, direct your attention to the back of the engine block, closer to the exhaust side. Given its placement, you might require a flashlight or adequate lighting to discern the number.

Dismantling the Quad 4’s serial number, the initial segment typically displays the engine’s year of production, followed by a letter delineating its assembly plant, culminating in a unique engine sequence number.

For illustration, consider 90A123456:

  • 90 elucidates its production year, 1990.
  • A stands for the Lansing, Michigan assembly plant.
  • 123456 represents its unique manufacturing order.

Engine suffixes offer a more detailed narrative:

  • LGO: Signifying a 2.3L DOHC High Output version, one of the popular variants.

Check out the links we included up above to find out how to decipher these.

14. Ecotec Engine Family

To discern the serial number on an Ecotec engine, focus on the engine block’s side, typically located near the exhaust manifold. Due to its strategic placement, ensure you have ample lighting to read the number without hindrance, and make trying to do a GM engine serial number lookup that bit simpler.

Delving into the Ecotec’s serial number, you’ll typically encounter the year of manufacture first, succeeded by a letter marking its assembly plant, and finally, a distinctive engine sequence number.

Let’s break down an example: 04L789012:

  • 04 pinpoints its production year, 2004.
  • L signifies the Spring Hill, Tennessee assembly plant.
  • 789012, the unique sequence number, highlights its individual manufacturing lineage.

Engine suffixes further enrich the narrative:

  • LE5: Denoting a 2.4L DOHC variant, one of the Ecotec family’s renowned members.

Those links and databases we mentioned earlier ought to have these sequences to help you decode them.

15. LT Engine Series

To unearth the serial number on an LT engine, you need to venture to the engine block’s front, typically right above the oil pan on the passenger side. Given the tight spaces in modern engine bays, arm yourself with good lighting to clearly identify the serial number.

Navigating the LT engine’s serial number, you’ll typically be greeted with the production year at the outset, trailed by a letter denoting its assembly plant, and wrapping up with a distinctive engine sequence number.

Let’s dissect an example: 18K654321:

  • 18 reveals its production year, 2018.
  • K stands for the Bowling Green, Kentucky assembly plant.
  • 654321 represents the individual engine’s manufacturing sequence.

Engine suffixes further amplify the story:

  • LT1: Referring to the 6.2L V8 engine variant, a crowning jewel in the LT engine line.

Check out those links we mentioned earlier to help you decipher and decode these sequences and codes.

16. Duramax Diesel

GM Engine Serial Number Lookup

To pinpoint the serial number on a Duramax engine, one should aim their gaze toward the lower center area on the driver’s side of the engine block. Given the Duramax’s substantial architecture, utilizing a flashlight or LED light can make this task notably more manageable.

When assessing the Duramax engine’s serial number, the format predominantly consists of an assembly plant code, production date, and a distinctive sequence number.

Let’s delve into an example: G0928-123456:

  • G represents the Moraine, Ohio assembly plant.
  • 0928 stands for the production date, translating to September 28.
  • 123456 is the individual engine sequence, marking its unique identity.

Engine nomenclatures further provide clarity:

  • LML: This nomenclature denotes a 6.6L V8 turbo diesel, a prominent member of the Duramax lineage, recognized for its efficiency and emissions compliance.

Those links we noted earlier might help you with decoding what these sequences mean.

17. Atlas I6

For those eager to identify the serial number on an Atlas I6 engine, it’s typically etched on the driver’s side of the engine block, near the middle. Because of its location and potential for dirt accumulation, using a flashlight or LED tool can significantly aid in its visibility.

Diving into the serial number, the Atlas I6’s code predominantly showcases an assembly plant indication, the year of production, followed by a unique engine sequence number.

Breaking down an example, J0310-678910:

  • J signifies the Moraine, Ohio assembly facility.
  • 0310 represents the production date, hinting at March 10.
  • 678910 pinpoints the engine’s unique manufacturing sequence.

Further demarcation in nomenclature:

  • LL8: This denotes the 4.2L inline-six variant, underscoring its position in the Atlas engine family, celebrated for its balance of power and efficiency.

Those links from earlier contain the data you’ll need to decipher this.


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