The Holley 1904 is a 1 barrel, downdraft carburetor and has three basic parts, the main body, throttle body and the float bowl. The main body includes the metering block, float and the economizer. The float bowl mounts on the front of the carburetor and can be metal, or glass. The glass bowl is becoming a rare piece to find, undoubtedly because they are so easy to break and they are not made any more.
Having the float bowl on the front allowed the 1904 carburetor to be designed with a low profile, which accommodated a smaller space between the engine and the hood. While we are fortunate to have carburetor kit coverage for all of the 1904 carburetor numbers, there are few other parts still available. We now produce both the brass float and plastic actuator.
There are some common problems with this carburetor and fortunately we know what they are and how to fix them. Because of over tightening of the float bowl screws, the main body is often warped causing leaks around the float bowl. This can be rectified by heating the body in a vice and straightening the mounts. Another common problem is fuel leaking past the needle & seat, causing a flooding condition and we have a process that will take care of this problem also. Due to years of wear the choke shaft often has excessive end play causing the idle screw to miss the fast idle cam and possibly cause the choke valve to hang. Last but not least is a problem with the metering block being warped and allowing fuel to leak past. This can be rectified by grinding the surface flat, which we do with a disk sander, but a flat file should also work. All of these problems are fixable and we have the cures, which are detailed on our Holley 1904 technical page and on our many Holley 1904 videos. It would be a good idea to review all of this information before jumping in to your rebuild.
Please be aware that any of our technical information is based on parts that you have purchased from us. Parts from other sources may install, or work differently.
Holley 1904 Carburetor Identification
Look for your carburetor number on
Float Bowl Leak
Watch a video about fixing the Holley 1904 float bowl leak.
Vacuum Check Ball
The 1904 carburetors for automatic transmissions have a nylon check ball and retainer clip that goes in the float bowl body where the throttle body mounts to the float bowl. The manual transmissions did not need this. In our Holley kit # 421, this check ball is plastic. This vacuum port is used to feed the
|Helpful DocumentsHolley 1904 Carburetor Identification, Parts List & Specifications.I.H.C. 4 Cyl. Metro & Scout Holley 1904-G Holley 1904 Adjustments
Installing the Needle & SeatThe 1904 tends to leak past the copper washer between the seat and the bowl. When installing the needle & seat apply a small amount of Permatex Red to the threads of the fuel inlet screw
(the screw that holds the seat). Also apply a very small amount of Permatex Anaerobic gasket maker to the washer (some are copper, some are fiber).1904 Float Bowl
The Holley 1904 glass float bowl and metal float bowl are interchangeable. The glass type of float bowl uses special screw clips. You must use these on the glass bowl, or it could break. The Holley 1920 float bowl will also work on the 1904, but the baffle will need to be removed 1st. The baffle simply slides in and out.
Adjusting the Accelerator Pump Stroke for Seasonal or Climatic Changes.
The accelerating pump stroke can be adjusted for seasonal or climatic changes by changing the position of the pump link in the throttle lever. The hole in the lever nearest the throttle shaft is the normal setting and should be satisfactory for nearly all operating conditions. If a richer accelerating pump discharge is desired for extreme cold weather operation, set the pump link in the outer hole in the throttle lever. Pump link position can be changed by removing the cotter pin at the lower end of the pump link, moving the pump link to the other hole, and re-installing the cotter pin.
Holley 1904 Rebuild Videos