Two basic numbers are attributed to each Holley carburetor: the model/series number and the list/part number. The series number indicates the general type, or series; for instance, 4150, 4160, or 4500.
The 4150 series is the original 4-barrel modular design, which features metering blocks and replaceable jets on both the primary and secondary sides. The 4150 series is available with either mechanical or vacuum secondary operation.
The 4160 series is a slightly less-expensive variant of the 4150, featuring replaceable primary jets, but with a thin metering plate on the secondary side and no replaceable secondary jets.
The 4500 series is the Dominator big-CFM racing series, with a larger main body and a unique secondary actuation linkage design.
The model number is not stamped on the carburetor, but it’s easy to identify by simply examining the carburetor. If the secondary side has a metering block with jets, it’s a 4150; if not, it’s a 4160. The Dominator is easily identifiable by its size and the shape of the throttle bores.
For all practical purposes, the “list” number is the part number of the carburetor; it is the top number stamped on the carb. The list number is also stamped on the choke housing/air horn of all Holley carburetors that have a choke housing. Keep in mind that the Dominator series and some other race carbs, such as the Ultra HP series, do not have a choke housing; their list number is stamped on the top of the main body.
The list number (also called the part number) appears on the face of the choke housing on carbs that have chokes. The word “LIST” or the letter “L” sometimes precedes the part number; these were used randomly and have nothing to do with the year of manufacture.
As seen in this example (a 4160-series 600-cfm carb), 1850 is the part number. Following the part number is –2, which indicates that this is the 12th update or change for this carb; this likely means that the dies have been renewed 12 times. For models that have been produced for decades, dies and tooling wear and necessitate updates in the manufacturing process.
You don’t need to be concerned with the “dash” number. The bottom number is the build date. The first three numerals represent how many days from the start of a year that a carb was made, and the fourth numeral is the last digit of the year of manufacture. This carb was produced on the 133rd day of 1974, 1984, 1994, or 2004.
This carburetor’s choke housing is stamped 80670-3, which indicates that this is a 670-cfm Street Avenger. The number shown below the part number indicates that it was built on the 160th day of a year ending in 4. Based on when this carb was purchased, this likely means 2014.
This HP carb, because it has no choke housing, carries its identification on the side of the throttle body. It is clearly marked as a 4150. Note the “HP” designation under “4150.” Under the word LIST appears the list, or part, number of 82851, which indicates that it’s an 850-cfm Street HP carb. The build date of 0471 indicates that it was made on the 47th day of a year ending in 1. Based on when this carb was purchased, it was likely built in 2011.
Street HP carbs have a vibratory polished body as well as smoothly contoured venturi inlets. All Holley carbs can be easily identified; simply use the part number stamped on the carb and search the database on Holley’s website.
Carburetors such as the Dominator 4500 series do not have a choke housing, and as a result, the part number and date code are located on the side of the main throttle body.
This example shows a list number (also known as the part number) of 8082-3, indicating that it’s a 1,050-cfm HP unit for a single 4-barrel installation. Depending on design, Dominators are available designed for 1 × 4 (one 4-barrel carb) or 2 × 4 (two 4-barrel carbs for a dual setup) mounted to the intake manifold.
Although 4150- and 4160-series carbs do not display the model number, the Dominator identification does include the series number, which in this case is 4500. The build date indicates the 203rd day of a year ending in 4. Since this carb was recently purchased, I assume that it was built in 2004 or 2014.
The list number may be preceded by either the word “LIST” or by the letter “L.” The factory used the word “LIST” or the letter “L” randomly. Don’t worry about it. Some carbs have it and some don’t.
For example, a LIST 3310 is a 4150 series with either a 750- or 780-cfm rating, depending on when it was made. Another example is a Street Avenger carb’s choke housing/air horn stamped with the part number (e.g. 80670), without “LIST” or “L.”
A dash followed by a single- or double-digit number may be found immediately following the part number. This dash number simply indicates that a running change for that particular part number of carb had occurred (perhaps a die was changed, or other evolutionary production change). A –1 indicates the first running change. A –4 indicates the fourth running change, etc. From a selection/purchasing standpoint, you don’t need to be concerned with this number.
Located underneath the part number is a four-digit number, which indicates the build date. For instance, a build date might be 1954. This indicates that this particular carb was built on the 195th day of a year ending in “4” (which could mean 1974, 1984, 1994, or 2004).
Although this may seem confusing, dating a Holley carburetor is generally not too difficult. A date code should appear below the list number. Older carburetors have a three-digit code, while carbs made after 1972 used a four-digit code. You can always call Holley’s tech hotline and ask a Holley technician to help decipher the date code, but remember, this number doesn’t have any particular use for you, so you really don’t need to worry about it.
Series 4150 and 4160
Holley 4150s and 4160s are built on similar platforms with a few distinct differences. They both have square bores; the primary and secondary throttle bores are the same size, in a “square” configuration, in contrast to a spread-bore that has smaller primary and larger secondary bores.
The 4150 is a square-bore carb with center-hung floats and dual fuel feed inlets, and replaceable jets in both primary and secondary metering blocks. The 4150 carbs with vacuum-operated secondaries have an accelerator pump and a power valve on the primary bowl, but no accelerator pump or power valve on the secondary bowl.
The 4150 carbs with mechanical secondaries are known as Double Pumper carbs; they have the addition of a secondary accelerator pump, and depending on the specific part number, may also have a power valve on the secondary side.
The Series 4160 carbs also have a square-bore pattern but with more basic features. The primary side has a metering block with jets, but the secondary side has a thin metering plate with pre-sized orifices.
Although a metering block has replaceable jets for tuning purposes, a metering plate (used in the secondary side of 4160 carbs) requires changing the metering plate for secondary “jet” size tuning. Metering plates are available in a range of main-hole and idle-hole configurations.