M-Block 351M/400 Technical Reference

Understanding Ford Part Numbers

Copyright 2002-2003 Dave Resch
All rights reserved.

Ford part numbers have three parts:

  • Prefix — identifies the year, vehicle type application, and the engineering department that designed the part (e.g., 1977 truck engine)

  • Main number — identifies the part generically (e.g., engine block, cylinder head, carburetor, etc.)

  • Revision code — identifies the revision level of the current part design.

The part number prefix usually consists of four characters:

  • A letter that identifies the decade (C=1960s, D=1970s, E=1980s, etc.).

  • A digit that identifies the year in the decade (0-9).

  • A letter that identifies the vehicle application type (A=full-size Ford car, T=truck, O=Torino or LTD II, S=Thunderbird, etc.).

  • A letter that identifies either the engineering department responsible for the design (B=body, E=engine, W=axle, etc.), or a “service” or replacement part (Z=service part).

The main part number usually consists of four digits, but occasionally it includes one or two letters, and it may have up to seven characters total.

The revision code consists of one to three characters that identify up to three levels of revisions. Revision codes always begin with a letter, followed by another letter or a number, and sometimes a second letter after a number. For example:


Part numbers vs. ID codes

Part numbers identify a part in the Ford parts catalog. When you buy a part from the parts department at a Ford dealership, they identify that part by its part number. Part numbers can change for reasons that have nothing to do with the part itself or any real changes to the part. Part numbers are often dropped or consolidated for simplicity in catalog listings.

Many parts have “ID codes” that are molded or cast into the surface of the part to help distinguish it from other similar parts. Sometimes the ID code is the same as the catalog part number, and sometimes it is not. It can get confusing when the ID code is different, yet similar to the part number.

On some cast iron parts, the casting ID code identifies the raw casting, and the part number identifies the finished, machined part. Engine blocks and cylinder heads are good examples of this. The casting ID code for an engine block is 6015, but the part number is 6010. The casting ID code for a cylinder head is 6060, but the part number is 6049.

If you find the casting ID code on an engine block, you might see the 6015 number, but if you order an engine block from a Ford parts department, they'll refer to part number 6010.

In the case of flywheels, sometimes parts for several different applications (with different part numbers) carry the same casting ID code, which represents the original application or design. Usually this happens when the same raw casting is used to make several different parts.

In many cases, the main part number (middle part of the complete part number) is not used in the ID code. That's because the main part number identifies the type of part generically, such as engine block, cylinder head, exhaust manifold, etc. If you're looking at the casting ID code on an engine block, you’re not likely to mistake it for a cylinder head or an exhaust manifold, so the engine block part number (6010 or 6015) is kind of superfluous for identification purposes.

Many ID codes use only the application prefix (first part of the complete part number) and the revision code (last part of the complete part number). For example, an engine block with the complete part number D7TE-6010-A2B may have a casting ID code of D7TE-A2B. The combination of application prefix and revision code is sufficient to identify a unique part.

Be careful about assuming that the application prefix alone can identify a part. In the case of truck-specific M-block parts, most of them carry the application prefix D7TE. However, sometimes a seemingly slight variation in the revision code identifies a part for a different, incompatible engine. For example, one harmonic balancer for the 400 engine has an ID code of D2AE-C, while ID code D2AE-A identifies a harmonic balancer for a 351W. Part numbers are D2AE-6316-C for the 400 balancer and D2AE-6316-A for the 351W balancer.

Sometimes the ID code has nothing to do with the part number. An example of this is crankshafts. The catalog part number for a 351M crankshaft is D7AZ-6303-A, but the casting ID code is 1K or 1KA.

When it comes to identifying the parts installed on a vehicle, the ID code is much more useful than the catalog part number.

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