Zenith Needle/Seat

[Nick in Fayetteville]

When I install my new Zenith needle/seat valve (modern), how many shims do I use to get the correct float level? It comes with one thick one. I ordered a pack with several of various thickness. Can the valve be used without any shims to include the one that comes with it? Thanks

 

[Jim/GA]

Nick, those are actually gaskets for the valve. You use as many as you need to get the float position where you want it. Mix and match thicker and thinner gaskets until your float is at the right level.

You must use at least one gasket or it will leak fuel internally. It does not have to be the one that came with the valve. I start out using one thick and one thin, then adjust from there.

You measure the distance from the machined surface of the carb top to the seam on the side of the float when the upper carb body is held upside down (gravity closing the float against the valve). You want that to be 1". If you are going to err from that, with the combination of gaskets chosen, go to a measurement slightly over 1" (which gives you a slightly lower fuel level in the bowl).

 

[Bob Bidonde]

These slides might help you understand:

 

[tunbecoming]

I purchased a set that included a variety of sizes. Can the valve be installed and operated without any additional shims?

 

[Jim/GA]

I purchased a set that included a variety of sizes. Can the valve be installed and operated without any additional shims?

You must use at least one of them, to serve as a gasket to seal the valve. Think of it as a gasket, not a shim.

I have never installed a valve that did not need at least one. I sometimes use 3 of varying thicknesses to get the fuel level I want.

 

[bobbader]

Here's the simple answer ................... There's NO SIMPLE ANSWER to this! There are 3 different type float valves available 1. original style, 2. Viton tipped, 3. Double ball. Within these three categories there may be more than one manufacturer. There are differences in the floats .............. 1. Original style manufactured by Zenith 2. Original style manufactured by Holley. 3. New foreign made reproduction. 4. New USA Made reproduction (Again multiple manufacturers of the reproduction units)

As Jim cannon suggests, you start with the gasket provided with the valve and add to it, with gaskets of different thicknesses, until you achieve the desired height. Re-read Jim's answer, above, to get the suggested measurement of the correct height.

As with many of these type operations, it helps if you can slow down your thoughts and execution of the process. Looking for the quick, easy, perfect answer to the puzzle doesn't always translate well while working on 90 year old cars. And, as with many of these type operations, you may need to perform the job more than once to get to the desired solution. If it doesn't work the first time, go at it again. If it still doesn't work .............. walk away from it, ask more questions, approach it one more time. You'll get there.

Good luck.

 

[tunbecoming]

One of these must be used to seal the valve, as a gasket. Instead of a shim, think of it as a gasket.

 

[larrys40]

Bob ,
You are exactly right . There’s no simple answer unfortunately. There may be some including suppliers that disagree but the iron tips don’t always work well. If the don’t hold vacuum my premise is they won’t hold fuel. I vacuum test them with a handheld vacuum pump and almost half seem to leak. Also I thin the crown of the tip and how it seats on the float is another issue. You have to make sure the float doesn’t have any divots and wear spots . A Dremel tool can fix that or find another good float.

I do find that sometimes the old fashioned steel seats do well as long as they pass the vacuum test. Great topic guys. More feedback is good .
Larry Shepard