You’ll find your GM camshaft identification numbers stamped on the rear end of the camshaft, typically featuring alphanumeric codes that reveal essential design information. Common prefix codes include “12” for standard Small Block Chevy hydraulic flat tappet applications from 1955-1987, “08” for hydraulic roller configurations post-1987, and “07” for LT1/LT4 variants. These markings may require timing cover removal to access properly, and understanding these codes helps determine compatibility and performance specifications for your specific engine application.
Quick Tips
- GM camshaft identification numbers are typically stamped on the rear end of the camshaft near the gear area.
- Small Block Chevy camshafts use prefix “12” for hydraulic flat tappet (1955-1987) and “08” for hydraulic roller (1987+).
- LT1 and LT4 camshafts feature the “07” prefix and have distinctive front-mounted distributor drive gear characteristics.
- Assembly plant letters like “V” (Flint) or “T” (Tonawanda) in the identification code indicate the manufacturing location.
- Remove timing cover to access ID numbers, or use precision measurement techniques to identify specifications without camshaft removal.
Where to Find GM Camshaft Identification Markings
Several specific locations on GM camshafts contain identification markings that help you determine the correct part for your engine application.
You’ll typically find identification numbers stamped on the rear end of the camshaft, especially on 3.6L LLT engines from 2009-2014. Additionally, engine types can often be identified through their unique camshaft specifications.
Some casting numbers appear near the gear area or lobes, though these don’t always indicate cam grind specifics. Factory GM camshafts were originally produced in-house before later production was outsourced to specialized suppliers.
Understanding GM Camshaft Prefix Codes
GM camshaft prefix codes serve as alphanumeric identifiers that reveal critical information about your camshaft’s design, compatibility, and manufacturing specifications.
You’ll encounter different prefix types that correspond to specific engine families, with codes like “12” indicating standard Small Block Chevy applications and “08” designating hydraulic roller configurations introduced in 1987. Understanding these prefixes helps you distinguish between roller and flat tappet designs while ensuring proper camshaft-to-engine compatibility during rebuilds or replacements. When verifying camshaft authenticity, check that the assembly date precedes your vehicle’s build date to confirm the component’s manufacturing timeline aligns with factory specifications. Additionally, it’s important to be aware of known engine issues that may affect the performance and reliability of your vehicle’s engine.
Common Prefix Code Types
Understanding prefix codes serves as your first step in properly identifying any GM camshaft, since these alphanumeric combinations reveal essential information about engine compatibility and application.
You’ll find numeric prefixes like “18,” “09,” and “56” on 4.3L V6 engines, while alpha-numeric codes such as LA0, LA1, LA3, and LA4 indicate specific displacement and design features across different engine families.
Engine-Specific Code Applications
When you’re decoding GM camshaft identification numbers, the engine-specific applications become essential because these codes directly correspond to particular engine families and their unique specifications.
Small block, big block, and six-cylinder engines each use distinct prefix codes that identify displacement, performance packages, and timing characteristics.
You’ll need to match your camshaft code with the correct engine family for accurate identification.
Roller Vs Flat Identification
Two fundamental camshaft designs dominate GM engines: roller and flat tappet systems, each requiring specific identification methods to guarantee proper installation and performance.
You’ll identify roller cams by their polished, rounded lobes and needle bearing presence, while flat tappet cams show distinctive wear patterns on flatter lobe surfaces.
Casting numbers provide definitive confirmation when visual inspection isn’t conclusive.
Small Block Chevy Camshaft Identification Numbers
When you’re working with Small Block Chevy engines, you’ll need to understand the specific prefix codes that identify different camshaft types and their applications.
Standard SBC camshafts manufactured from 1955 to 1987 use a “12” prefix in their part numbers, which indicates they’re designed for hydraulic flat tappet lifters in the traditional small block design.
However, if you’re dealing with 1987 and later engines, you’ll encounter hydraulic roller camshafts that carry an “08” prefix, signaling the shift to roller lifter technology that required modified blocks and lifter valley configurations. Understanding common engine issues during the rebuild process can also help you choose the right camshaft for your specific needs.
Standard SBC Prefix Codes
Since Small Block Chevy engines dominated GM’s production lines for decades, understanding their camshaft identification numbers becomes essential for anyone working on these powerplants.
You’ll find prefix codes starting with assembly plant letters like “V” for Flint or “T” for Tonawanda. These single letters identify where GM manufactured your specific camshaft during production.
Hydraulic Roller Cam Identification
Hydraulic roller camshafts brought significant changes to Small Block Chevy identification methods starting in 1987, requiring you to look for different visual cues and numbering systems than those used on earlier flat-tappet designs.
You’ll notice these cams feature stepped noses and smaller bolt patterns.
Most hydraulic roller SBC cams use the “08” prefix code, while LT1 and LT4 variants use “07.”
Hydraulic Roller Cam Identification Codes
Although identification numbers on hydraulic roller camshafts can appear confusing at first glance, understanding their location and format will help you decode your GM cam’s specifications with confidence.
These codes typically include grind numbers combining intake lobe, exhaust lobe, and separation angle measurements.
You’ll find markings stamped on the camshaft’s rear end, sometimes requiring timing cover removal for visibility. Additionally, recognizing camshaft performance factors can assist in understanding how these specifications impact engine behavior.
LT1 and LT4 Engine Camshaft Markings
When you’re identifying LT1 and LT4 camshafts, you’ll find that many use an “07” prefix code system stamped on the rear section of the camshaft.
This numbering system helps distinguish these specific engine variants from other GM camshaft applications, though it doesn’t provide complete specification details.
You can typically locate these markings near the distributor drive area at the back end of the camshaft, where the stamped numbers are most accessible during inspection.
“07” Prefix Code System
GM’s prefix code system serves as an essential identification method for LT1 and LT4 engine camshafts, providing technicians and enthusiasts with crucial specification data stamped directly onto the camshaft body.
You’ll find these alphanumeric codes typically include prefixes like “GMPT” for GM Performance Team cams, followed by numeric sequences indicating lobe lift, duration, and manufacturing details for accurate identification.
Distributor Drive Location
Beyond the standard prefix codes, LT1 and LT4 camshafts feature a distinctive physical characteristic that sets them apart from conventional small-block Chevy engines: a front-mounted distributor drive gear.
You’ll find this gear integrated into the camshaft’s timing gear assembly, which drives the OptiSpark distributor system. Traditional small-blocks use rear-mounted distributors, but LT1/LT4 configurations place theirs at the front.
V6 Engine Camshaft Prefix Codes
Although GM V6 engines share similar designs across different models, each camshaft carries specific prefix codes that prevent costly installation mistakes during engine assembly or repair.
You’ll find RPO codes starting with “LA” followed by numbers, like LA1 for 3.4L V6 engines or LA3 for 3.2L DOHC variants, ensuring proper camshaft compatibility with your specific engine configuration.
Reading Camshaft Specifications and Cam Cards
When you’re working with GM camshafts, understanding how to read cam cards becomes essential for proper engine performance and avoiding costly mistakes.
Focus on key specifications like lobe lift, duration at 0.050″ lift, and lobe separation angle.
You’ll multiply lobe lift by rocker arm ratio to calculate actual valve lift, while duration measurements tell you how long valves stay open.
Identifying Camshafts Without Complete Removal
You don’t always need to pull the entire camshaft from your GM engine to identify what you’re working with.
Remove the timing cover to access ID numbers stamped on the cam’s front end.
Use calipers to measure lobe lift by finding the height difference between each lobe’s highest and lowest points, then cross-reference these measurements with manufacturer catalogs.
Measuring Cam Lobes for Unknown Profiles
Someone who encounters an unmarked camshaft can determine its specifications through precise measurement techniques that don’t require specialized equipment or extensive disassembly.
You’ll need a micrometer to measure the base circle diameter and lobe lift. Start by measuring the intake lobe’s advertised lift, then use manufacturer databases to match your measurements with known grind specifications.
Distinguishing Between Hydraulic Roller and Flat Tappet Designs
After you’ve measured an unknown camshaft’s specifications, the next step involves identifying whether it’s designed for hydraulic roller or flat tappet lifters.
You’ll notice roller cams have perfectly flat lobe surfaces, while flat tappet cams feature a mild taper.
The lobe profiles differ greatly—roller cams allow steeper ramps and more aggressive timing due to reduced friction.
Troubleshooting Worn or Missing Identification Numbers
When camshaft identification numbers become worn, corroded, or completely missing, several factors typically contribute to this frustrating situation.
Cast numbers suffer damage from mechanical wear and cleaning chemicals during rebuilds. Stamped markings at camshaft ends erode from improper handling or non-specified tools.
Aftermarket cams often lack standard GM identification, while counterfeit parts complicate verification through original numbering systems.
Wrapping Up
You’ll successfully identify your GM camshaft by locating the stamped numbers on the cam’s rear journal or thrust surface. Cross-reference these codes with manufacturer specifications to determine lift, duration, and lobe separation angle. If you can’t find markings, you’ll need to measure the lobes directly using a dial indicator. Remember that hydraulic roller cams have different identification patterns than flat tappet designs, so you’ll want to verify your engine’s tappet type first.