Holley 1920 Leaking Diaphragm

A customer was asking me about the hole that is located on the bottom of the main body (bottom of the float bowl. See the illustration and notice the small hole next to the mounting flange. His carburetor is leaking through this hole and it shouldn't be.

This hole is the relief, or indicator hole coming from behind the accelerator pump diaphragm. What does fluid coming out of this hole indicate? 1. The diaphragm could be ruptured allowing gas to get behind the accelerator pump diaphragm. 2. The metering block that cover the diaphragm could be warped (so many of them are because of the way they are tightened down), allowing fluid to get past the block and into the dry area of the diaphragm socket. The solution to #1 is easy, rebuild the carburetor, replacing the diaphragm. While #2 isn't quite as easy, it isn't a big deal either. Use a flat faced grinder to grind it flat and if that isn't available, then use a good flat file and file it flat. As a last resort, you can apply a small amount of Permatex anaerobic gasket sealer around the edges of the diaphragm.

Now if you just rebuilt the carburetor and need to replace the diaphragm, then keep in mind that there are several different diaphragms available for the Holley 1920. The differences are the stem length, stem is flat, or round and the cutout pattern on the diaphragm gasket area.

When you tighten the block down, start from the middle and work your way out, tightening the screws a little at a time.


Greg Cunningahm

Date 9/26/2013

Hi guys, I have a 1985 F-150 with the straight 6 300 and a 1 barrel carb. However it is not the Carter, it has been replaced by a Holley 64-1600. (The only carb on the planet you don't show parts for). What's the deal with the 64-1600 and why is there such limited info on the net?


Date 9/30/2013

The 64-1600 is a Holley part number. Your carburetor is a Carter YFA (late model).


Date 10/21/2013

I have just replaced my Holley 1920 with a rebuilt 1920 I purchased from Rock Auto on my '69 slant six. It starts fine and idles fine, but it runs really rough. I had already done a complete tune up, set the timing and the dwell. Any ideas?

Ed Kolodziej

Date 11/4/2013

Good morning don't see a listing # for my carb.would like to purchase a rebuild kit, mine is 2#s first 1798 & 4162 for my 1920 carb thanks

Soren Nelson

Date 2/17/2014

Subject:Holley 1920 Pump Rod length for International Body:Mike, I ordered what I thought was a correct rebuild kit for my Holley 1920 List 4542 (the 338 kit). When rebuilding the carb, I noticed that the new Pump Push Rod Sleeve did not fit properly on the end of the pump rod in the kit. After comparing the old and new rods, I noticed that the new rod was about 3mm longer, and the gap in the new rod being about 4mm longer than the old one. I am wondering if the reason mine is diffrent from other 4542 1920s is because it is fitted to run an automatic transmission. Is there any way to get a Pump Diaphragm from you with a rod that is 31mm(1.218)long, with an 8mm(0.312)gap 3mm(0.125) from the end?

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