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post #1 of 47 Old 07-30-2019, 12:10 PM Thread Starter
michael72
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New Weber Carb

I just purchased a Weber K551-38 with the electric choke after an epic battle with rebuilding my Carter BBD. I did not upgrade the Viton needles based on some advice from Weber as I am not going to do any heavy off-roading. I also purchased the adapter to use the original air filter.

I made these decisions based on all of the advice available on this site so I want to thank you in advance for any advice you can give me.
Here is what I plan on doing:

- Nutter Bypass: I know how to do it but I do not know if there is something I should do differently with this carb. Do/should I do this before I install the new carb?

- Team Rush Upgrade: I know how to do it but I do not know if there is something I should do differently with this carb. Do/should I do this before I install the new carb?

- Vacuum cleanup: I have read many posts about vacuums and I am as lost as I can possibly get. While doing this, I would like to cleanup as much as possible. This is where I am the most lost.

- Original Air Filter: Different posts and Weber gave me the impression that, for mostly daily driving, there were pros and cons to both. I like the look and would like to keep it. There are vacuum actuated flaps on the filter inlet, can I still use these or is there a correct way to disable them?

- Fuel Pressure Regulator: I have seen some people use them and some people use a fuel filter with a dual outlet, which is what I have. That filter looks like it may have something to do with the vacuum/vapor system so if I can get rid of that by using a pressure regulator, I would like to do so. What setting should I be looking for if I should use one?

- Installing the Carb: Any specific advice about installing this carb would be very helpful as well.

This is my sixth Jeep (4th CJ7 and two previous YJís) so I hope to be familiar with what you send me. I was a mechanic in the Air Force as well but the vacuum system in this thing has beaten me. Thank you again for your help.

Michael

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post #2 of 47 Old 07-30-2019, 12:59 PM
John Strenk
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Quote:
Originally Posted by michael72 View Post
I just purchased a Weber K551-38 with the electric choke after an epic battle with rebuilding my Carter BBD. I did not upgrade the Viton needles based on some advice from Weber as I am not going to do any heavy off-roading. I also purchased the adapter to use the original air filter.

I made these decisions based on all of the advice available on this site so I want to thank you in advance for any advice you can give me.
Here is what I plan on doing:
Quote:

- Nutter Bypass: I know how to do it but I do not know if there is something I should do differently with this carb. Do/should I do this before I install the new carb?

- Team Rush Upgrade: I know how to do it but I do not know if there is something I should do differently with this carb. Do/should I do this before I install the new carb?
This is a tough one I feel it should be done first but if something gets screwed up, it would be hard to tell if it was a ignition problem or carb problem.
I would say do it as careful as you can to be sure it won't add to your problem.

Quote:
- Vacuum cleanup: I have read many posts about vacuums and I am as lost as I can possibly get. While doing this, I would like to cleanup as much as possible. This is where I am the most lost.
Plenty of diagrams to do it for a weber and a good idea to eliminate any vacuum leaks

Quote:
- Original Air Filter: Different posts and Weber gave me the impression that, for mostly daily driving, there were pros and cons to both. I like the look and would like to keep it. There are vacuum actuated flaps on the filter inlet, can I still use these or is there a correct way to disable them?
Definitely a do on the OEM housing. The flaps work independently of any other system. all they need is a manifold vacuum source to work correctly.

Quote:
- Fuel Pressure Regulator: I have seen some people use them and some people use a fuel filter with a dual outlet, which is what I have. That filter looks like it may have something to do with the vacuum/vapor system so if I can get rid of that by using a pressure regulator, I would like to do so. What setting should I be looking for if I should use one?
The OEM filter will prevent any vapor lock from the fuel in the lines. and it will maintain the proper pressure easily with no reliance on springs or or other things on a pressure regulator.
Simple and effective .

It has nothing to do with the vacuum/vapor system on the rest of the engine.

Quote:

- Installing the Carb: Any specific advice about installing this carb would be very helpful as well.
All I know is to make sure your adapter is flat. Many will put sandpaper on a glass sheet and sand it a little to be sure the surface is flat to avoid vacuum leaks.

Choose a Weber 38 for your application. But i see you did already

Quote:
This is my sixth Jeep (4th CJ7 and two previous YJ’s) so I hope to be familiar with what you send me. I was a mechanic in the Air Force as well but the vacuum system in this thing has beaten me. Thank you again for your help.

Michael
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post #3 of 47 Old 07-31-2019, 11:20 AM
Matt1981CJ7
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If the engine currently runs with the BBD, I'd do the Nutter first. Make sure that's working before moving on to the carb and/or distributor.

I wouldn't bother doing the Team Rush on your current distributor. It has a lazy advance curve intended for the computer. A pre-'81 Duraspark distributor, or several aftermarket distributors, will have the proper advance curve for your Nuttered engine.

Absolutely keep the OEM air cleaner assembly. It's vastly better than those dinky breathers they put in the Weber kits.

Here's a simple vacuum layout that worked well on my 258 with a Weber 38. Let us know if you have any questions.

Matt
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post #4 of 47 Old 07-31-2019, 11:41 AM
Shawn Watson
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I can't really add much other than to agree with John and Matt that you're better off fixing your vacuum routing and any ignition upgrades prior to installing the Weber. I'd also take the time to set the timing to 10* with the vacuum advance removed and plugged. Once that's done, reattach the vacuum hose to the brass fitting that hopefully resides under your carb on the manifold.

So you're not breaking your neck looking at the engine, pull the carb out of the box right on the kitchen counter and set the throttle plates (idle speed screw) a half-turn in from contact with the lever. You'll need to hold the choke plate open and cycle the throttle open and let it close to disengage the fast-idle and make sure it doesn't re-engage while you're working on it. With the choke disengaged, just back the idle speed screw out until there's clearance, slowly make contact with the lever again and go in a half-turn from there. Then just use your fingers to run each mixture screw in until it seats and back it out one and a half turns.

Hopefully that'll be good enough to fire up and see what mixture screw setting it wants after it's warmed up and the choke is off.


Shawn

Edit: You may as well pull an idle jet to make sure what size they are. There's a large, brass screw on each side of the carb. Just pull one out and look for a number stamped on the side of the jet.
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Last edited by Shawn Watson; 07-31-2019 at 12:18 PM.
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post #5 of 47 Old 07-31-2019, 12:12 PM
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Everyone here has covered just about everything, except upgrade to an H.E.I. which eliminates the need for a "Nutter By-pass" and figuring out how much your emissions dist. total advance is, and no need for the extra expense in the cap rotor upgrade "Team Rush".

Michael...
- "Fuel Pressure Regulator: I have seen some people use them and some people use a fuel filter with a dual outlet, which is what I have. That filter looks like it may have something to do with the vacuum/vapor system so if I can get rid of that by using a pressure regulator, I would like to do so. What setting should I be looking for if I should use one?"

Most on this forum and everywhere else use the Original fuel filter. This is a pressure regulator. Some of the "off shore" filters may not have a restriction in the filter's return to the tank fitting. So you would get a Wix or a Napa "Gold" which I've heard is a Wix. This will keep the pressure to the carburetor at less than 3 lbs. Most are running 2 lbs.

The idea of the Viton needle, is the original Weber needle is Brass, this doesn't hold much pressure, and when bouncing around it holds less pressure. This is why the Viton is recommended, and it will hold around 9 psi before leaking.

Mr. Shawn (as always) has some good advice about checking your idle jet before installation. REDLINE uses a .55 mm and we here on this forum have found some that have not been changed.

Good luck, there are plenty of people here that can get you through your initial set-up.

UTN
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post #6 of 47 Old 07-31-2019, 01:33 PM Thread Starter
michael72
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Geez guys, thank you very much! I will read up and get going tomorrow or Thursday. The carb should be here Thursday or Friday. I will probably be posting more questions before then. What a nice group of people. Thank you again.
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post #7 of 47 Old 08-01-2019, 01:50 PM Thread Starter
michael72
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The carb is scheduled to be here on Monday so I have some time to clean out my workbench and get ready. All of my questions look like they are involved with the vacuum system.

I have read through all of the posts and here are my new questions:

The Jeep was running before I decided to get into a fight with the Carter BBD so doing a nutter with or before this install should not be a problem as far as future trouble shooting.

I can wait to do any ignition upgrades such as a team rush or other after I get the Jeep running again.

The fuel regulator information makes sense to me now. The metal line coming out of my fuel filter that is connected to the vapor system is rusted, does anyone know where to get one?

All three of these get involved with the vacuum/vapor system somewhere. This is where I get lost. Everything seems connected.
If I went downstairs tonight with the intent of doing a nutter and cleaning out as much as I can from the engine compartment before the carb arrives, what should I do?

Thank you again,

Michael
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post #8 of 47 Old 08-01-2019, 02:34 PM
Matt1981CJ7
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I'd go to this site and familiarize yourself with each individual vacuum system:

https://gleebledorf.com/list.html

Then navigate to the "What Controls What" page on that same site. Anything that is controlled by the computer, or feeds info to the computer, can be safely removed when you Nutter. That will leave you with a very basic engine configuration consisting of the components shown in the diagram I posted above.

Hope this helps,

Matt


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post #9 of 47 Old 08-01-2019, 05:22 PM Thread Starter
michael72
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I will get into the info and start cleaning things out. The diagram that you posted still doesn't make sense to me so I am going to post some pictures of my engine compartment so that you can tell what is what. My wife an I have been looking at diagrams for two weeks. I have the service manual and I think it made it worse. As frustrating as this is, I have read enough posts to know that I am not the only one. Thank you again.

Michael
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post #10 of 47 Old 08-02-2019, 01:53 AM
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If you are running an electric fuel pump and cannot verify it supplies at or below 6psi, consider going back to a stock mechanical pump after the carb is running. The original system is designed to run at low pressures with good volume and does not require a FPR. If you feel an electrical one is better, I suggest the solenoid type is $10 and hyper reliable and only pumps 3-6psi, safely within the range of a Weber inlet valve. All pumps should have an inline filter before them, protects the pump from tank rust particles and allows you to see fuel flow

Also, change out any lengths of hose and put tube in, it is safer as it does not melt, the only hose you should have had after the fuel pump was at the filter. A Weber comes with a barbed fuel fitting so you will need a new piece of hose here but I would suggest a short piece and a steel tube up to the filter. clamps should be the constant force kind, not jubilee clamps, they are easy to overtighten and the hose then cracks over time (though I do use them, I really shouldn't)
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post #11 of 47 Old 08-02-2019, 06:06 AM
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Michael,

What part of the diagram are you and your wife struggling with?

Matt


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post #12 of 47 Old 08-02-2019, 11:39 AM
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Quote:
Originally Posted by Matt1981CJ7 View Post
Michael,

What part of the diagram are you and your wife struggling with?

Matt
Michael,
I have to agree with Matt,
"What part of the diagram are you and your wife struggling with?"
The diagram picture Matt posted (#3) is what "most" everyone uses.
This is a very clear, simple vacuum layout.
IMHO

UTN
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post #13 of 47 Old 08-02-2019, 12:32 PM
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I thought the Nutter Bypass was for the emissions Jeeps with the ECU? The bypass basically took the computer out of the mix.


I'd do the distributor/ignition mods.


If you like the look of the old air filter, keep it. It will not make a difference Most people who go with the Weber carb like the smaller profile Weber air filter, but either one will work.


My experience with doing the Weber conversion on a YJ 6 cylinder, the fuel pressure regulator was only used if you had a problem, not something that is required. As noted in a prior post, stay with the mechanical fuel pump. They are noisy, but do the job and simple to fix/replace down the road.
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post #14 of 47 Old 08-07-2019, 11:11 AM Thread Starter
michael72
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I removed the computer from above the heater box and pulled the wiring harness.

The black and green wires running from the distributor and coil Trace back to split loom on the driver's side firewall. There is an orange wire coming out of the loom that I have lost track of. Black to distributor, green to coil, orange to...?

Where the wires meet the back of the fuse box, not sure what I should leave. Some wires run to a six prong plug that was attached to the wiring harness connected to the computer. The plug is marked on the back A-F, D & F run directly into the back of the fuse box.

Thank you!
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post #15 of 47 Old 08-07-2019, 11:59 AM Thread Starter
michael72
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Figured out how to post pictures.

Picture 1: Black to distributor, Green to coil, where does the orange one go?

Picture 2: The plug remaining after removing the computer harness. What can I remove?

Picture 3: The previous owner got deep into the electronics, I found splices everywhere, about 20, all made with duct tape. Most of it got cleaned up but he made a jumper wire from the back of the fuse box over to the coil and spliced it into the red and white striped wire going into the coil and then the solenoid.

Picture 4: The wire spliced into the back of the fuse box.

Any advice on how to get this cleaned up right?

Thank you,

Michael
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