[grizzy67]

This is a vacuum diagram for the Weber carb or basically what I have except I do not have the CTO valve and EGR valve. If you remove those lines from the diagram that is exactly how I had mine setup. Right now I just disconnected the Dist line and capped it. I'm a bit confused about putting a Tee and check valve in the line?
I think there is a spring unhooked inside the Dist. because after timing and reattaching the vac line to the Dist you can watch the vac advance seemingly all the way advanced. HEI is scheduled to arrive today. If I get all the instructions read and I can borrow my neighbors heated garage I might have it in this weekend. Check compression, Balancer alignment and timing chain slack. But that's a long list because I have to replace a hydraulic line on my plow today and a few more chores.

 

[Boojo35]

I did not say for you to add a check valve. You misunderstood my post. Your engine has a manifold vacuum source that has the port into the intake which has a rubber hose attached to it, then a check valve and then a plastic vacuum line.

I really thought that I described it very thoroughly, but this should help.

The green arrow points to the manifold vacuum port. The Blue arrow points to the check valve that you already have. The red circle is where you need to install a tee. So, the rubber vacuum line in the red circle..... This is what you are going to replace with a new piece of line and a tee. Get a new piece of vacuum line, of the same ID and a tee that fits it. You are going to need a slightly longer piece of line than you have. Put a piece of rubber line to the intake port. (green arrow) Put your tee into that vacuum line. Put another piece of vacuum line on the upper side of your tee. And then put your check valve (blue arrow) into that line on the upper side of the tee.

You are simply replacing the rubber hose in the red circle with two pieces of vacuum line and a tee.

Now move your distributor vacuum line from your carb to the Tee and cap off the port at the carb. This removes all doubt about you having intake manifold vacuum to your distributor that is not influenced by the venturis on the carb at all.

YOU ABSOLUTELY DO NOT WANT TO INSTALL THE TEE ABOVE THE CHECK VALVE. IT NEEDS TO GO MANIFOLD PORT, RUBBER, TEE, RUBBER AND THEN CHECK VALVE.

And yes. When you do this your vacuum advance will pull to full advance at idle. That is what you want. That is normal. That does not indicate a worn distributor.

Your vacuum advance provides full advance under two conditions, Idle and cruising with a very light load on the engine such as level road or even going downhill. When you are at cruising speed and start to go up a hill or grade, your engine load increases. When the engine load increases, the motor will ping easier but your manifold vacuum will drop because the engine is under load. Because the manifold vacuum drops in that condition, so will the signal to the vacuum advance. This means that your timing will back off correspondingly because the vacuum advance does not pull as far with less vacuum

I seemed to have confused you or you are reading too much of somebody else's material and confusing the two. I do not know.

The reason I suggested that you move your distributor vacuum connection to this point is your own posts that indicate that knock off vs real webers are inconsistent on what this vacuum port does and IMO it is too wishy washy and I do not believe that you have a vacuum gauge or totally understand engine vacuum under different operating conditions. This method removes all doubt.

 

[grizzy67]

Well I wasn't thinking of that vacuum port because I haven't heard of using it for dist use. So yes that part was a bit confusing. Good explanation! I see where your going.
I did get the HEIl dist and plan on installing is soon, doing several tests and checks before so I know everything is within tolerances.
As for the Weber carb comments, I might have confused you. I wasn't complaining that it was a bad unit, I was looking for comments on personal experience of the knock off carb's performance over time. I don't have enough time with my carb nor know exactly what has been done to it because it's not in it's original state.
i do have a vacuum gauge,. I haven't put it on that port that I can remember but when I hooked the dist line back on I could see the advance arm of the dist move (my thought) more than it should. I also have used the vacuum gauge to set the timing. connected to manifold port I was getting 20hg of vacuum setting the idle. It still pinged between 55-60mph. That's what made me question whether the carb was properly jetted.

 

[grizzy67]

BooJo, Thanks for your time. You have been teaching an old dog some new tricks. I've always done the mechanical work on our vehicles. Getting this YJ has been a challenge as it's not in it's original condition pertaining to the engine. Never really had to understand the details of how carburetion, ignition are working together. Besides timing an engine and being done with it I'm now challenged to understand how these things are functioning together during the course of idle through acceleration. My pre concept was that timing was a constant increase as RPM's increased and not variable vacuum conditions. And then add carburetion to the mix.
Seeing that all modifications to my YJ were done by PO's I don't know what all has been done. i'm challenged to figure out what has been done and what needs to be done to get it running correctly through out the spectrum. Just waiting for time and weather to get in a warm garage!

 

[Boojo35]

Wait until we get started on how vacuum is really a pressure differential and how it all effects fuel delivery also. LOL.

This is kind of random but yet this thread was leading me down the path of trying to figure out how to explain a few things about vacuum and I stumbled into a writing by MOTOR that states that ported vacuum can never exceed intake vacuum.

Guardair 79SG012 $58.29 Pistol Grip Syphon Spray Gun | Zoro.com

I will just drop this link here to prove that ported vacuum CAN exceed intake vacuum. There are things known as venturies and what they can do is cool.

 

[grizzy67]

Wait until we get started on how vacuum is really a pressure differential and how it all effects fuel delivery also. LOL.

This is kind of random but yet this thread was leading me down the path of trying to figure out how to explain a few things about vacuum and I stumbled into a writing by MOTOR that states that ported vacuum can never exceed intake vacuum.

Guardair 79SG012 $58.29 Pistol Grip Syphon Spray Gun | Zoro.com

I will just drop this link here to prove that ported vacuum CAN exceed intake vacuum. There are things known as venturies and what they can do is cool.

Boojo, did you copy the wrong link, it not MOTOR? or is this an example? I do have a couple of old MOTOR manuals from the 70's on the shelf. If I get a change maybe I'll if there is anything interesting write ups in them.
Yes, this is getting interesting because fuel delivery is moving to the top of my list.
I did do a quick check with my new timing ligt and found that at idle the port on the carb is pulling around 18 degree's. I should have wrote it down but ot was cold and I had something else to do.

 

[Boojo35]

No. The link is something that you put an air pressure hose to and you squeeze the trigger and air pressure runs through it and believe me it is all pressurized but somehow the hose on it can siphon liquids up and add them to the pressurized air stream. It creates a low pressure/vacuum to siphon but yet it being totally pressurized debunks when MOTOR said that ported vacuum cannot be below manifold vacuum. I am just saying that there are venturi effects and different ways to use them that makes that totally not true in all situations.

 

[grizzy67]

I had a feeling the link was an example. That keeps me on track with lean mixture as a contender. There can stitl be some area in the carb restricting the fuel delivery. I don't know if there is an adjustable linkage between the primary and secondary or if it is a solid linkage. Wrong size jets causing a lack of fuel as the throttle opens while vacuum decreases.
I did get a chance to pull down the MOTOR's manual. They have a troubleshooting section. Pre-ignition, ping causes were described as timing, lean mixture, carbon deposits, exhaust valve adjustment, the air/fuel mixture being to warm, lack of coolant circulation etc. Nothng really stood out. I do put some of these things lower on the list because the engine was rebuilt 25,000 miles ago and it idles very smoothly. There was one think they said that sticks out is that it can be only one area and not across the whole engine, one valve, spark plug etc.
Another thing is the ignition module, does it still have the ability to change anything after being Nuttered? With the new HEI dist it can be totally eliminated. Just throwing out some thoughts here.

 

[grizzy67]

Just a little update
As I had talked about installing a HEI Distributor and do some checking. I went through the compression check. All but one were even within a pound or 2. The third cylinder had a significant drop but still within the tolerances. Added a little oil to the cylinder and it was up to the rest of the cylinders. I didn't go any further seeing numbers were within tolerance.
Next was to check for any slack in the timing chain, I found that to be in good condition.
Last was to install the new dist. labeled everything and set up TDC for number one cylinder. marked position of the rotor and then pulled the old dist out. Installed the new HEI , regapped the plugs and installed the new SP wires 8mm. I removed the ignition module and found the heavy power wire, I believe it was yellow. This is what the directions said to use as a power source as it is key on power. run a wire to the dist and hooked up the tach wire. Set the timing accordingly and she started right up. So far I've done a little idle adjustment and set the timing.
Now for the results. I've been driving the Jeep for the last couple of weeks now. What a difference it has made. There is more power and to my amazement the ping is all gone. I have yet to fine tune the engine with my vacuum gauge yet and the weather is to cold to worry ATT.
I just disassembled the old dist and don't see visually anything that might have been the problem. The PO had just replaced the dist cap, rotor amd plug wires. I'm going to guess that the problem was either in the dist electrical or the ignition module was having problems or the combination of all including the coil.
Problem solved, time to move on to some more cosmetic details, solve a water leak. Always something to do! Thanks for all info and suggestions given.

 

[Boojo35]

Thanks for the update. We love success stories. Congrats on seeing it through.

I wonder if the nutter bypass had been totally done. The ignition module did have the ability to change timing electronically. It had to in order to make a knock sensor work in the system. I will not even try to explain how it did it but lots of guys praise their results when changing over to an HEI.

 

[grizzy67]

Thanks for the update. We love success stoTy

I wonder if the nutter bypass had been totally done. The ignition module did have the ability to change timing electronically. It had to in order to make a knock sensor work in the system. I will not even try to explain how it did it but lots of guys praise their results when changing over to an HEI.

I was thinking the same thing, I was leary of most everything one of the PO had done. I never did fully read the instructions for the Nutter bypass I assumed it was done correctly once I saw the twisted pair of wires. Oh well, water under the bridge. We’ll see how things go from here. I’m still not sure about my topic of this thread, Weber carb jets

 

[Boojo35]

You got the pinging to go away and that is critical. That will destroy and engine by melting down pistons and valves. Like melt them like you took a torch to them. Bad news.

Your YJ must have pinged horribly because it is really difficult to hear a spark knock in one with a soft top or top off.

Now you can move on to your Jetting issues but quite honestly, most carbs are pretty close out of the box. A given amount of air needs a given amount of fuel. Too big of carb on an engine introduces some really bad and not tuneable issues. You have an arguably slightly undersized carb which should perform very well. Its limitation will be higher RPMs.

I would drive it a while and really honestly assess how it runs, how it smells, what the economy is and Jeeps do not have good economy. And last. Look at the plugs after a while to make sure that they are not sooted up.