Holley Car and Truck Carburetors
Buying a replacement part for your vehicle can be an intimidating experience. So, before you select a Holley car or truck carburetor, arm yourself with a few basics.What are Holley carburetors made from?
Most Holley carburetors are made of aluminum to reduce the part's overall weight. They may have a die cast, cast aluminum, or billet aluminum body.
- Holley die cast aluminum carburetor: This unit is composed of various metals such as zinc, aluminum, and copper.
- Holley cast aluminum carburetor: Holley parts made from this material are considered mostly pure. Rarely, the part may contain fewer than 3% of other metals.
- Holley billet aluminum carburetor: This part is made from metal bars, making it structurally sound. Additionally, it is machine-carved into shape as opposed to being poured into a mold.
When you are replacing a unit or performing a rebuild, you need a six-digit number to determine the carburetor’s identity. Early units have stamped numbers. Search for laser-etched numbers on Holley carburetors. The number's location differs per model. See below for common places to find them.
- Locate the identifying number for Holley four-barrel carburetors like the 4150, 4160, 4165, and 4175 on the choke tower’s face near the vent tube. Part numbers may be separated by a dash, such as 12345-6.
- The Holley 4150HP or 4150 Ultra XP numbers are located in different locations, depending on the model. Earlier units have the number listed on top. Search the throttle-level side of the main body for succeeding models.
- Look on the side and top of the choke tower, as well as the backside of the main body to find the identifier for two-barrel carburetors, like the 2300 model. If the carburetor does not have a choke tower, search the top.
- On the first generation 4500 series, look on the raised rings around the Venturi for identifiers. Check the throttle side of the main body of second and third generation units.
To adjust the carburetor, you’ll need a flat head screwdriver and a wrench. The fuel pressure range for Holley carburetors is between seven psi at idle and five psi at wide-open throttle. With tools in hand, follow the steps below to adjust your Holley carburetor's fuel levels.
- Run the engine and remove the site plug from the primary float bowl.
- Slacken the screw on the lock.
- Turn the nut counterclockwise to raise the level and clockwise to lower.
- After tightening the screw, return the site plug and duplicate the process on the secondary site hole.
Loosen the small screws on the electric choke and turn the cap counterclockwise. Only move the cap one notch at a time until you reached the desired tension. Then tighten the screws. Next, check the positive terminal wire with a switched source to make sure it reads 12 volts when the ignition key is in the on position.
- Make sure the engine is cold before making adjustments.
- Do not turn the cap past the index marks
- If the electric choke delays opening, rotate the cap clockwise.