Holley 1904 Carburetor

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 donor.

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.

Get your Holley 1904 parts here.
1904 Carburetor Kits

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
the pad just left of the float bowl. Example: cdte 9510 A. In this case cdte is what you are looking for. Add the A as in cdte-a. When this fails, try to match up a part number from the carburetor, that may be stamped on various parts, with the list from the parts list pdf file below.
Holley 1904 Carburetor  identification, Parts List & Specifications.
PDF File

I.H.C. 4 Cyl. Metro & Scout Holley 1904-G

Holley 1904 Carburetor Manual

Float Bowl Leak

Most 1904 carburetor these days have warped bodies where the float bowl attaches. The biggest problem with the fit of the 1904 floatbowl is not the bowl itself. Rather, it is the presence of so much warpage in the main body surface to which the bowl mounts. I know of no other way to fix this than the way that I use: put the main body in a press, heat it up and press straight the “ears” to which the bowl mounts. Yes, after I get it as straight as it is going to be I dress the gasket with some Permatex Anaerobic Gasket Maker, but that will do you little good without a reasonable straight main body.

Watch a video about fixing the Holley 1904 float bowl leak.

Vacuum Check Ball

Holley 1904 Carburetor

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
distributor advance vacuum line.

Helpful DocumentsHolley 1904 Carburetor Identification, Parts List & Specifications.I.H.C. 4 Cyl. Metro & Scout Holley 1904-G Holley 1904 Adjustments
Installing the Needle & Seat

The 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.
Holley 1904

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

18 thoughts on “Holley 1904 Carburetor

  1. Hello – I have (2) 1904 Holley carbs, both with warped bodies. As you suggest to heat the body up and put it in a vice to straighten it out, if I sent you the carb can you provide this service and rebuild. I have been thru 8 rebuilt carbs and all have had this same problem, leak around the float bowl. Thank you, Mike

  2. I rebuilt Holley 1904 with Carburetor Repair Kit Premium. After I installed on car (1930 Model A with Miller OHV), I turned on fuel pump to check for leaks and the main nozzle was dripping fuel into the venturi. Even after turning the pump off, fuel continues to drip from nozzle. Could this be the float settting? Fuel too high in the bowl dripping out nozzle? There is no fuel is dripping out the balance tube, so I believe the float needle is closing as expected, but from other techincal answers on this site, I should recheck for leaks around float valve, too. Thank you. David

      • Yes, thank you, resolved! (I tried to reply earlier this week, but link to Holley 1904 did not work me). I found your note about sealing the fuel inlet seat screw and gasket. Fuel was leaking ahead of the inlet valve, overfilling bowl and then dripping out main nozzle. Took carb off, opened bowl, inverted to close float and put air pressure through inlet. With a drop of oil on seat gasket, air bubbles were easy to see originating from gasket. Added the recommended Permatex anaerobic sealant to gaskets and red locktite to threads. Passed the air test. Back on the car, no drip even with fuel pump on. On the computer screen, zooming in on figures in the original manual really helped me understand carb passages. Next, I think I need to get linkage to close throttle plate tight; engine starts great and then roars way over idle, even with idle screw closed.

  3. Mike I have a 1904 list 2352 on an 1961 IHC Scout 80. I bought the repair kit and when I went to relace the check balls in the metering block mine has plugs not screw caps as in your video. Do I have the wrong metering block and does it matter. I saw on your site that the used Metering block you have for sale is described as a 2454 and is non-threaded. Is that what mine is? Do you have the correct ones? I also noticed that my float has “wings” for lack of a better description, on each side. A large one on the inside and a smaller one facing the cover. is this the wrong float? Should I remove the wings?

    • Metering blocks can have plugs instead of screws. That is why we include new plugs in our 1904 hardware kit. The plug type have to be drilled out, cleaned well and then re-plugged. Assuming you didn’t use a bit too large, the new plugs will fig snugly. Optionally apply a very small amt of JB weld around the plug.

      The winged type of float is perfect. I suspect they designed them that way to help take the bounce out of the float.

  4. When I left off on my Model A with Holley 1904, the rebuild had went well, and I was adjusting the idle mixture screw. I was finding that when fully seated and backed out 2 turns, there were very few threads, maybe three, engaged in the body of the carb. The screw, even with spring, was a sloppy fit that seemed like it would vibrate loose and fall out. I wrapped a tiny bit of teflon tape on the screw threads and the fit was more secure, but not right. My time was up, and I had to put car into winter storage. Looking at the old needle that I was replacing, despite it’s very worn condition, I think that it had a much shorter taper and tip, which allowed more threads to engage in the body before the tip hit the seat. I am thinking buying another one (or two) mixture screws and turning a shorter taper. Would this seem reasonable? Are the mixture screws available separately or only in the screw kit? Thank you.

    • 1st of all I doubt your problem is with the screw unless it is simply the wrong screw. When you have to turn a mixture screw more than normal, it is indicative of a dirty carburetor needing rebuild, or perhaps a vacuum leak.

      Idle mixture screws for the 1904 are only available in our hardware kit.


  5. I have a holley 1904 on a 1955 IH R100 that i’m restoring. Carb was rebuilt. It idles just fine, no leaks, the issue i’m having is when i give it a throttle input the truck dies. If i give it a shot of starter fluid as it wants to die the truck revs up and then i can continue to rev up as long as i don’t let it come back to idle. I’m assuming that this is indicating a fuel delivery problem. Can you help steer me in the right direction. Any help would be appriciated. Thanks in advance.

    • There is a whole array of things it could be. Obviously it isn’t getting enough gas. Float level, clogged passage ways, wrong accelerator diaphragm (happens a lot when buying the wrong kit), plugged, or damaged main discharge, leaking past the metering block, low fuel pump pressure.

      Most likely when doing this on acceleration only, you can home in on the diaphragm, or main discharge area.

  6. I have a problem with a holley 1904 carb.The truck will only run with the choke fully closed.Geting past idle is impossible, very hard to start.have to dump a large amount of fuel in just to get it going. Thankyou.

  7. I have a Holley 1908 (close cousin to the 1904). I have rebuilt it, properly I hope but the one problem that persists is that the Rambler dies when I slow and make a right turn. It only happens on right turns. I have adjusted the float level up and down by about a 1/16th of an inch and I have made adjustments to the idle mixture and idles speed. Nothing seems to work. The economizer valve seemed to work normally (the little plunger was free) when I rebuild the carb. I’d like any advice you can offer. Thanks.

    • My guess is casting warpage, probably in the metering block. It would seem that fuel sloshing to the left side of the bowl is somehow getting together withe manifold vacuum which is what often causes this sort of problem — think Carter WCFB in left-hand turns when the fuel sloshes to the right side of the bowl and gets together with manifold vacuum to the choke P/O.

      It could be accelerator pump related; ask the customer if it stalls in those right-hand turns only if he tries to accelerate.

      Here is something I found that might help:

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