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. In particular the float and the plastic actuator are very rare these days. We get quite a few requests for these parts, but when we do find these parts, they generally go on other 1904 carburetors. Your best bet to obtain these parts is to find a used carburetor and use it for a parts doner. There are only a few types of carburetors that we will rebuild these days and the Holley 1904 is one of them.
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.