Setting the metering rod in a Carter WO carb.

[Carls_jeep]

Comparing the metering rod setting tools

In an effort to find the easiest or best way to set the metering rod I did a comparison of the Carter tool, the Snap-On tool and the Home made tool. I have three metering rods and jets to use to compare with a borrowed Carter tool and a Snap-On tool and my own Home made tool.

The jet has a tapered opening of 116 deg with a hole of .070� +.000 -.0002� as measured in the three jets I have. The metering rods vary in length from the start of the tapered area to the spot the pin rests on. The OAL length of the rod from the spot the pin rests on to the tip also varies as shown below in the drawing. I also used one of the cleaner jets to measure the OAL of the bottom on the jet to the shoulder of the tool for a reference and they are as follows:

Carter tool, shoulder to bottom of jet = 2.947�.

Snap-On tool, shoulder to bottom of jet = 2.946�.

Home made tool, shoulder to bottom of jet = 2.945�.



Below is a photo of the Carter, Snap-On and Home made tool. The tip angles and lengths of the tools vary as follow.

The Carter tool has a tip angle of 58 deg with an OAL from the shoulder to tip of 2.782�. The length of the shoulder to contact area in jet is 2.720� and may be 2.718� as it�s hard to read a line scratched in * clearly on the surface of an extremely rough finish.

The Snap-On tool has a tip angle of 42 deg with an OAL of 2.804� from shoulder to tip. The length of the shoulder to contact area of the jet is 2.718� and was clear to read because the tip was very smooth.

The Home made tool I made has a tip angle of 36 deg with an OAL of 2.761�. The length of the top end to the contact area of the jet is 2.719� The tip on my tool is as smooth as the Snap-On tool.



I measured them several times to be sure I was as correct as possible. I used dial calipers along with a 10 power glass and a jig to hold the rods as I made the measurements. I also used a Peak brand 10 power comparator to do the small measurements. I was as careful as I could but some readings could be off a thousandth or two.

Here is a drawing of the Home made tool from the internet that I made to save you from looking it up. I paid close attention to getting is exact as possible and it must have worked as will be shown in the following tests of all three tools. You will note a dotted line on the drawing that indicates where I gound away half of the diameter for about �� down the shaft to clear the backing washer on the pin where the metering rod sits. Since the Carter and Snap-On tools are flat stamped metal and the rod is 1/8� diameter there will be some interference so don�t force it or you will get a false reading.



Now for comparing them on the carb on my Jeep. When I checked my current setting it had .005� free travel of the rod with the throttle screw backed off all the way to close the throttle plate. That means with a dial indicator on the top of the rod I could move the rod up .005� while holding the throttle closed.

When I put the Carter tool in place of the metering rod I had to loosen the nut and reset the pin and tighten the nut. When I checked the free travel using the metering rod I now have .040� free travel using the dial indicator as noted above.

Then I removed the metering rod and installed the Snap-On tool and the setting was the same as with the Carter tool. As I moved the tool I could just feel it touching the bottom of the pin.

Then I removed the Snap-On tool and installed the Home made tool and the result was the same. Moving the Home made tool under the pin I could just fell the tool as it rubbed the bottom of the pin.

All three tools gave the same setting of the metering rod pin. I wasn�t expecting that they would be that close but they are.

If you don't own a Carter tool, Snap-On tool or home made tool you could set the metering rod with a dial indicator on a mag base. It has to be a mag base with adjustable arms that most likely only a machinist would own. Use a very flat metal bench or a drill press table. Clamp the carb to the table and use the dial indicator with the plunger tip on the top of the metering rod. It has to be lined up exactly straight in line with the metering rod. Loosen the nut on the pin so it has a slight drag and then move the pin down to touch the metering rod. Then raise the metering rod until you have traveled .040" on the indicator and lock the pin nut. Check the travel again to be sure it is .040" and if not repeat until it is .040". You should then be at the setting you would have using a factory or home made tool.

Because of the differences in the dimensions of the metering rods and possibly the jet don't expect replacing the metering rod and jet in an overhaul without resetting the pin to end up with the correct setting. It could be way off.

[Carls_jeep]

We had a long discussion on the CJ2A site about the metering rods and jet and how to set them. I did this article to find out how to set them without a factory tool. I tried to be as exact as possible so it would be a valid test. My Jeep had .005" free travel of the metering rod the way I set it when I overhauled it. I don't remember where I got the method to set it and began to wonder about the setting and I was also having trouble with cold starts.

Doing the test I found that with all three tools the free travel is .040" and it is now set that way. I will be test driving it to see if it has cured my problems and I feel it will do that because that is the factory setting.

I wanted to share what I found with those on this site.

[Gunslinger]

Wow, Carl, thats a lot of work, thankyou!  Maybe Bob would put that out on his web page onthe tech link area so it doesnt get lost in a post.

[Carls_jeep]

Well, I guess it was but I wanted to settle a question in my mind that has been bothering me since I rebuilt my carb. I am glad I did this because I think I have solved my cold start issue with the correct adjustment of the metering rod.

[calvinhunt]

Carl,
  I agree with Gunslinger, that's a lot of work.  But I think many of us will benefit from your efforts.  I've printed of the info and saved it in my Carter Overhaul Manual.  Thanks.  

[Bob W]

Maybe Bob would put that out on his web page onthe tech link area so it doesnt get lost in a post.

I can do that if it is okay with Carl. It will take a few days to put it up.

[Carls_jeep]

That's fine with me Bob. The reason I measured every thing and recorded all the comparisons is so we can understand what is going on with setting the metering rod. It looks like the home made tool will do the same job as a factory tool or you could use a dial indicator if your careful and understand what your doing. This lets everyone make up their mind what method they want to use to set the metering rod.

[Bob W]

I think the dial indicator method is cool. That is within reach of most people. Carl, do you have any photos of that method?

[Carls_jeep]

I'll do some photo's next week.

[Carls_jeep]

In the photo below I have the dial indicator set up on the exh. man. and against the head in a spot where it is solid and doesn't move. You have to back the throttle screw off 6 full turns to be sure the throttle plate is closed. The plunger is set on the metering rod with the plunger as straight in line with the metering rod as I can get it. Then I set the dial on "0" to start to set the rod. Then you loosen the pin nut just so it will slip, push the pin down gently on the metering rod loop bottom and then with tweezers lift the rod until the dial indicator shows .040" and lock the pin nut. Check the travel by moving the metering rod up and down between the jet and the pin and it should still be .040". If not reset it until it is. It is important that the plunger tip touch only the metering rod and not the washer on the pin.



Setting the metering rod on the bench is a little easier but you still use the same method as above while the carb is clamped to a drill press table. See photo below. The tip I used in the dial indicator has a flat face but didn't screw all the way in the plunger but it is bottomed out in the threads. You can use the rounded tip that comes with the dial indicator but you have to be very careful to get it centered on the metering rod and not touching the pin washer to get a good reading. Most people would find it easier using the Carter tool or a home made tool.

[Bob W]

Thanks Carl, I am working on putting this info together in a web page.

[Carls_jeep]

Sorry about them not being sharp photo's. I tried several shots for each, bench and Jeep, and because of the distance and lighting those are the sharpest I could get with a full view of everything. It's the concept that's important anyway and anyone doing it has to have the ability to think out the process and understand what they are doing.

[macrisel]

Wow Carl........that is some great info!  I hearby give to you a Six Sigma black belt.

Use it only for the power of good... 8-)

[Bob W]

I have copied this information to my website here......

http://www.cj3a.info/tech/meter.html

Thanks Carl for taking the time to write this up.

[Carls_jeep]

Your welcome Bob. The reason I did that is to see if all the methods really worked and just what differences there are in the parts and the setting tools. Manufacturing tolerances are sometimes big and in the case of the metering rod and jet they can vary a lot, so much so that if you do a rebuild and don't reset the metering it can be way off.

If I had a CNC lathe I would make and sell the home made tool but alas I don't have a CNC lathe.