Small Block Chevy Engine Code

How to determine Small Block Chevy Engines

The Small Block Chevrolet engine, a successful marvel since the 1950s, featured in production vehicles up to the 2000s. With millions made over 50 years, various versions emerged, differing in heads, compression, and cubic inches. 

It’s easy to determine which SBC you have. Just look under the hood of your ride. Two sets of numbers will help: the first being Casting Numbers and the second, Stamped Numbers. Casting Numbers, as their names imply, are cast into the block when made. 

You’ll find them on the driver’s side, rear of the block, near the flange forward of the bell housing. They give general information about the engine. For example, 140029 indicates it was made between 1980 and 1985 and is a 350 cubic-inch engine. For more specific information, check the Stamped Numbers. 

These are literally stamped on a machined pad in front of the passenger side cylinder head, often covered up by the alternator. They tell you where the engine was assembled, the production date, and the suffix code. 

Remember, these numbers might be machined off when they deck a block. They are less important when you’re trying to quickly identify if it’s a 283 cubic inch motor or a 400 cubic inch one.

In automotive history, understanding the small block chevy engine code can be confusing. It’s important to get the right information. The main things to look at are the Engine Code and Partial VIN. These decode the car’s details. 

Don’t forget the casting number, it’s key. You also need to check the dates. The engine code and partial vin help you find out about the car quickly and accurately. Everything else will make sense once you know these. 

The small block chevy engine code stands as a testament to precision engineering. This code, a series of characters stamped on the engine, reveals its birthplace, capabilities, and identity.

1. Decoding the Engine ID

Every engine ID code is a unique identifier. For instance, V0101CLJ signifies the engine was assembled in the V plant, in January (01), on the first (01) day. The suffix CLJ indicates its application in terms of RPO, transmission type, and horsepower. Similarly, T0830CTY decodes to the Tonawanda plant, August (08) 30th. These codes don’t just mark the engine, they narrate its journey from a plant to a vehicle model.

2. Assembly Date and Machining Intricacies

The assembly date is crucial, often predating the car’s build date. Any mismatch here is a sign that something’s amiss. Moreover, machining processes like decking can obliterate these vital codes, posing challenges in historical verification.

3. Unveiling Power and Heritage

These codes also unfold the engine’s power saga. The CTY code, for example, represents a 1970 396 Camaro, boasting 375 hp and an 11.0:1 compression ratio, paired with a TH400 transmission. It’s not just about the numbers; it’s about the engine’s essence.

In essence, the small block chevy engine code is more than alphanumeric characters; it’s the DNA of automotive legacy. These codes are not merely identifiers; they are the storytellers of engines, each number and letter holding a piece of history.

Stamping Codes:

CodeEngine Plant
FFlint (Motor)
KSt. Catherines, Ontario (McKinnon Industries Canada)
MGM of Mexico
SSaginaw Service
VFlint (Engine)
Stamping Codes

Small Block Chevy Casting Numbers

The casting date for a Small block Chevy is crucial for identification, typically located on the driver side rear of the block, near the flange forward of the bellhousing. For Big block engines, this information is found on the right side above the oil pan rails.

  • Casting Date Location: On a Small block, the casting date is located at the rear of the block on the driver side, close to the flange by the bellhousing. For Big block engines, the date is on the right side, above the oil pan rails.
  • Decoding the Casting Date: The casting date code, like E038, reveals much: E indicates the Month (May), 03 is the Day, and 8 is the Last digit of the model year (1978). The month codes run from A (Jan), B (Feb), C (Mar), D (Apr), E (May), F (Jun), G (July), H (Aug), I (Sep), J (Oct), K (Nov), to L (Dec).

This coding is essential for tracing the Chevy’s assembly date and model year, a key part of its historical identity.

Understanding Small Block Chevy Casting Numbers

While reading, casting numbers are crucial. These numbers tell a story about the engine’s capabilities and design.

  • High Power and Low Power: The High Power rating indicates the maximum HP this block was used for. Low Power reflects the lowest rated horsepower for the RPO engine. This range offers insight into the engine’s versatility and potential output.
  • Main Caps and Engine Strength: The Main Caps are vital, indicating the number of bolts holding the cap. A two-bolt main, compared to a four-bolt main, shows significant differences. Four bolt main blocks are more desirable in high performance applications due to their extra strength and additional bolts that keep the bottom end more rigid and less prone to failure. However, a properly prepared 2 bolt main engine can also work fine. Often, issues arise with the rod bolt, not the crank, even in engines with “only” a 2 bolt main.

Understanding these aspects of a small block Chevy engine—its power ratings and the construction of its main caps—provides deep insights into its performance and reliability. The design, whether for a high-powered application or a standard build, reveals the engine’s potential and durability.

YearsCastingCIDLow PowerHigh PowerMain CapsComments
19553703524265195_2car, no filter
1955-5637209912651952252car, truck
1957-5937377392832202902car, truck
1958-6135565192832car, truck
1958-6237565192831703152car, truck
1958-6337942262831701952Car & truck
1961-6237899352831703152Late 61 car & vette
1962-6338348122831701952car & truck
1962-6537828703272503752car, truck
1962-6638648122832302car, truck
1962-6737898173272102752car, truck
1962-6737907212831702202Chevy II
1964-6638348102831952202Car, truck & marine
1964-6737913623272503002Replaced 3790721
1964-6738581743272car, truck
1964-6738581743272753502Full, A & Y
Casting Codes

VIN Code Format

The vin code format is stamped onto engines to provide essential identification. This format includes the divisional identification number, model year, assembly plant designation, and the vehicle serial or sequence number.

  • Historical Context of VIN Codes: In 68-69 model cars, the VIN number of the car where the engine was installed was stamped either next to or under the engine code ID. This practice linked each engine to its original vehicle.
  • Changes in VIN Stamping Locations: Starting in 1970, the serial number began being stamped in new locations, such as above the oil filter, on the block pad in front of the cylinder head, or on the transmission flange. Chevrolet issued technical service bulletins to guide which engines received a vin stamp, leading to some variations in the process.

Example of VIN Code Format: A typical VIN code format example, like 13N100001, decodes as follows: 1 represents Chevrolet, 3 is the year 1973, N stands for the Norwood plant, and 100001 is the production sequence of the vehicle VIN.

While understanding the VIN code format reveals much about an engine’s origin and history. It’s a crucial tool for identifying and authenticating engines, especially in classic car restoration.

In 1972, plant codes changed to reflect the VIN code. For example, “NOR” = Norwood before 1972. In 1972 and on, it was simply “N”. Below given are the assembly plant list for ease:

Plant CodeLocation
CLansing (B)
FFlint (Chevy)
HFlint (Buick)
LVan Nuys
PPontiac (Pontiac)
SSt. Louis
SRamos Arizpe
VPontiac (GMC)
WWillow Run
1Oshawa #2
2Moraine (T&B)
2St. Therese
3Detroit (T&B)
3St. Eustache
5Bowling Green
6Oklahoma City
8Fujisawa (Japan) Luv
9Detroit (Cadillac)
9Oshawa #1
0GM Truck Pontiac
Plant Codes

Suffix Portion of Chevy Engine Code

The suffix codes play a pivotal role, either alphabetic or alphanumeric, representing a specific portion of the alphabet. For example, if you’re exploring the code DZ, you would refer to the segment DTR-HQ.

In some cases, these suffix codes are reused multiple times over the years. Thus, in the event of a duplicate, it’s advised to check the partial VIN code or the block casting date code. This helps determine the year the block was made and consequently pinpoints the exact application your block was originally used in. 

Although the available list of codes is extensive and a summarization of the broader picture, it is not complete nor all inclusive.

Engine CodeYearCIDApplicationEngine VINHPBBLSGM Body/Comments
3N1978305U LG31452Firebird/school bus
3T1978350L LM11704Firebird/school bus
3X1978305U LG31452Phoenix/school bus
9A1980305H LG41555full size/school bus
AAA1976350m/tLF51602C-50 & 60/school bus
AAD1975350m/tLF51602C-50 & 60
AAJ1976350a/tLF51602C-60/school bus
AAK1976350LF51602C-60/school bus
AAL1976350LF51602C-60/school bus
AAM1976350LF51602C-50/school bus
ABA1978350LF51602C-50/school bus/Omega/Monte/Malibu
ABB1978350LF51602C-50/school bus
ABC1978350LF51602C-60/school bus
ABD1978350LF51602C-60/school bus
ABM1978350LF51602C-60/school bus
ACA19733501552C-50/school bus
ADA19733501552C-50/school bus
ADR1973350LPG fuel1552C-60/school bus/Impala
AJD19733501552C-50/school bus/Monte
AJH19733501552C-50 & 60/school bus/Impala
AJT19733501552C-30 & 35
AWA1989350L98, a/t8225TPIFirebird
AWK1989350L98, a/t8225TPIFirebird/Omega
BMK1990350L98, a/t8235TPIFirebird
C1957265m/t, 3 spdcars/Vette/Omega
C1958283m/t, 3 spd1852cars
C2K1977305LG3U1452F X
C2L1977305LG3U1452F X/Omega
C2M1977305LG3U1452F X
C2R1982305Roch E4ME carb.H LG41554B F G/Monte
C2S1982305Roch E4ME carb.H LG41554B F G
C2T1982305Roch E4ME carb.H LG41554B F G
C2U1982305Roch E4ME carb.H LG41554B F G/impala
C2W1982305Roch E4ME carb.H LG41554B F G/Monte
C2X1982305Roch E4ME carb.H LG41554B F G/Omega
C4A1984305Roch E4ME carb.H LG41504B F G/Impala
C4B1984305Roch E4ME carb.H LG41504B F G
C4C1984305Roch E4ME carb.H LG41504B F G/Omega
C4D1984305Roch E4ME carb.H LG41504B F G/Omega
C4N1982267Roch E2ME carb.J L392A B/Monte
C4P1985305Roch E4ME carb.H LG41504B F/Monte
C4R1982267Roch E2ME carb.J L392B G
C4R1985305Roch E4ME carb.H LG41504B
C4S1982267Roch E2ME carb.J L392B
C4T1982267Roch E2ME carb.J L392B G/Omega
C4U1982267Roch E2ME carb.J L392B G
C4W1982267Roch E2ME carb.J L392B G/Impala
C4W1984305Roch E4ME carb.H LG41504F B/Omega
C5P1985350Tuned port inj.6Parisien/Monte
C7A1985305Roch E4ME carb.H LG41504B F G/Omega
C7B1985305Roch E4ME carb.H LG41504B F G
C7D1986305Roch E4ME carb.H LG41504F
C7H1986305Roch E4ME carb.H LG41504F
C7L1987305Roch E4ME carb.H LG41504F/police/taxi/Monte
C7M1987305Roch E4ME carb.H LG41504F/Kingswd
C8B1979305LG3G1302F X/Impala
C8X1980267Roch E2ME carb.J L392F/Monte
CAR1972350tur 350, Calif emis1652A B
CAR1985305Roch E4ME carb.H LG41504F/Monte
CAT1972400t/h trans, CalifLF62B
CAZ1972307Powerglide NB21302A F X/Monte
CB1963283m/t, police, h/pcars/Monte/impala
CBG1971350Powerglidefull size/Impala
CCA1971307manual trans.2002A F X
CCC1971307Powerglide2002A F X/Monte
CD1957265m/t, 0. D.2car/truck
CD1958283m/t, 0. D.1852truck/1271/lmpala
CDA1972350m/t, CalifL651652A X
CDA1981350m/t, fed., L816Vette/Monte
CDB1972350Powerglide, CalifL652A B/Monte
CDB1982267Roch E2ME carb.J L392B G
CDC1982267Roch E2ME carb.J2B G/Monte
CDD1972350t/h NB2L48200Camaro/Impala
CDD1972350tur hydro, Calif1754Chevelle
CDD1972350t/h NB21652Monte
CDD1982267Roch E2ME carb.J2B G/Omega
CDD1985305Roch E4ME carb.H LG41504B G F
CDF1985305Roch E4ME carb.H LG41504B F G/Omega
CDG1972350m/t NB21754Chevelle/SS/Omega
CDH19723504 spd, NB2K2004Vette/Omega
CDH1985305Roch E4ME carb.H LG41504B F G/Bel Air/Kingswd/Omega
CDJ1972350base, tur 400, NB2K200Vette/SS
CDJ1982267Roch E2ME carb.J2B G/Bel Air/Kingswd/Monte
CDJ1985305Roch E4ME carb.H LG41504B F G/Impala
CDK1985305HO E4ME carb.G L691754Z-28[T/A/SS
CDL1972400t/h trns, pol/taxiLF61702Caprice
CDL1985305Roch E4ME carb.H LG41504B F G/Impala
CDM1972400t/h, pol/taxi, CalifLF61702Caprice
CDM1985305HO E4ME carb.G L691754Z-28/T/A/SS/Impala
Engine Code Suffix

Numbers Matching

In the context of small block chevy engine code, the term “numbers matching” is crucial. It means the engine or transmission of a vehicle can be matched to the one originally used in that vehicle. This matching is done through the PARTIAL VIN stamp on the component.

 If the partial VIN on the engine or transmission matches the vehicle’s VIN, it’s considered “numbers matching”. Some might use “numbers correct” to describe a close match, but remember, it’s not the same as “numbers matching”. 

The term holds particular importance when decoding special models like Z28 or Super Sport, where the VIN alone doesn’t identify the vehicle’s specific traits. In such cases, decoding the engine’s code to see if it matches the vehicle, especially for Z28 or SS equipment, becomes pivotal.

In extreme cases, it’s also essential to verify if the numbers stamped on the component are original and not restamped. The goal is to decode and figure out the vehicle’s authenticity and history.


In conclusion, the data provided in this article sheds light on the Small Block Chevy Engine Code, offering valuable insights for both beginners and enthusiasts. Drawing upon my own experience and expertise in the field, I can affirm that understanding these engine codes is essential for anyone looking to work on or modify Chevy small block engines. By deciphering these codes, you can unlock a wealth of information about your engine, making it easier to find the right parts and ensure optimal performance. So, whether you’re a seasoned mechanic or just starting your journey into the world of engines, mastering these codes is a key step towards automotive success.

Frequently Asked Questions (FAQs):

How do I identify my Chevy small block engine?

To identify your Chevy small block engine, you’ll want to look for the casting numbers. These numbers can be found in the corner, but they might be covered in grease and grime, so you might need some degreaser to clean them up.

How can you tell a 350 from a 327?

To distinguish a 350 from a 327, you can check the back of the crank. If it goes straight, it’s likely a 350 because they built it using a 350 crank and 350 heads.

How do you tell a 305 from a 350?

You can tell the difference between a 305 and a 350 by looking at the bore size. The 305 has a significantly smaller bore, about a quarter of an inch smaller. Chevrolet also had other small blocks like the 307.

What engine is this 3970010?

The GM engine block with the number 3970010 was used as early as 1968 for some 327ci engines. From 1969 to 1979, it was used for 350ci engines. It could be either a 2 or 4 bolt block used in cars, trucks, and even Corvettes. This casting number, 3970010, is quite common for small block engines.

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