[LeadfootCJ7]

Ok, I have been working on my CJ quite a bit lately to cure the problem of it running rich and smelling terrible every time I drive it. It's an 81 CJ7 258 with 4.0 head, HEI, and Weber 38 DGES. I am in Houston so basically sea level. The timing is roughly 10 degrees. I have adjusted it slightly several times to see if it helps, but I have not observed significant impact. Historically I have run as much as 18 degrees with the HEI setup and it ran fine. For purposes of getting the carb setup right I wanted it closer to the factory setting which is 8 degrees +/-2.

Background. I had tons of problems with the stock carb for years. Finally purchased this Weber carb 10+ years ago (don't remember exactly how long). I have a Carter electric fuel pump. The Jeep ran night and day better than the stock carb so I was happy and didn't care that it ran rich. Did a 4.0 head swap probably 5 years ago. Runs great, but still rich. I never really had enough time that this project made it to the top of the list. Recently that changed so I am tackling it since the carb needed a rebuild and had run horribly the last year or so. The accelerator pump was leaking gas so it helped make the rebuild happen. After the rebuild the Jeep runs better, but still rich.

I had some extra jets (long story) so I was going to run through the tuning guide and see if I could make it run. After some tinkering, I think I need different jets than I have in my possession. Technical help from weber is lacking so I am hoping some folks here might have some experience to help.

Turns out there are 2 different places to get weber carbs. Redline and weber carbs direct. Redline has significant technical information and help. When I called and was talking to them they asked me what color my electric choke was. Once I told them they let me know that I did not have their carb, but rather a "rip-off" of their design and to call weber carbs direct. :frown2: I have called weber carbs direct and am waiting to hear back, but googling leads me to believe I won't get much technical help. I wish I had known this when I ordered. I remember several places selling them and just picked one.

I do have a holly fuel pressure regulator so fuel delivery is right around 3 psi.

With the jets that the carb came with (45 idle jets, 145 main jets, and 170 air jets). It will not run without the idle speed screw opened up several turns which allows the progression port to be exposed. Due to that there is no way to adjust the idle mixture screws to in a way that lets me know if I need larger or smaller jets. However, it appears I need larger jets based on this. I had 50 (primary idle jet) and 60 (secondary idle jet). I swapped those in and it is better. Still rich, but it will idle with the idle speed screw only open 1/2 turn (progression port is not exposed until roughly 1 turn (I verified this when the carb was off the Jeep because I knew it would be important later on). I know the idle jets should match. I need to order jets, but want to be in the ballpark and don't want to keep ordering jets over and over. With these jets in, I can get the jeep to run better/worse and by adjusting the idle mixture screws. The secondary side is obvious. The primary side not as much. This leads me to believe 60 is closer to the size I should need.

I know several on here have experience so I was hoping you might have some experience to offer some advice on jet sizing. I have found some mention in random places on the internet that saw I should be running 60's for idle jets, 150/155 for main jets, and 180 for air corrector jets. Other places seem to contradict this.

Below is what came in the carb new setup for sea level (supposedly)
Idle Primary 45
Idle Secondary 45
Main Primary 145 (they claim it should have been 137, but that is not what is stamped on it)
Main Secondary 145
Air corrector 170's

Additionally I have the jets below to play with
Idle Primary 50
Idle Secondary 60
Main Primary 135 & 155
Main Secondary 135 & 155
Air corrector 160's & 180's

Any insight to point me in the right direction would be helpful.

Right as I was finishing typing this I got a call from weber carbs direct. The guy I talked to did not seem too technical, but did try to help. His immediate solution was just to throw 40's in for idle jets until I pointed out it would not run on 45 and seemed to improve with larger (although mismatched) jets. They he said just to split what I had and run 55's. I am not sure there was much thought put into that. I can spend a ton of $$$ ordering a whole bunch of jets and playing with them, but I would rather have some idea or some input from those who have experience before doing do.

 

[tsanchez23]

Oh yes...Weber Carbs Direct... I dealt with them on a 32/36 last year and they are not well-versed technically. I ran their carb for about six weeks before Matt here recommended I call Tom at Redline and get a real Weber.

I got the 38 and I've had my own issues with it running rich (black exhaust, gas smell, flooding out in traffic or after parking for a bit...) but I spent some time working on it last weekend and I actually vocally threatened her with spending the $1K to grab a throttle body injection to install. Funny thing - She started to run better shortly thereafter. Not sure if it was the work, or the threat, LOL

What I did:

Before this past weekend, I had done many things but not changed any jets. Per Tom, my carb was jetted correctly for what I needed and he didn't want me to touch it. My last advice from him was to drill 1.25mm holes in each throttle plate to let in more air. I did this and while it made things better, it wasn't by much.

This weekend:

I have a stock type fuel pump. I removed the two-port fuel filter and replaced it with a single in/out generic that now sits just to the side of the engine - right out of the pump and away from the heat of the manifolds. then I routed a long rubber fuel line around the front of the engine and as far from the manifold as possible to my Holley regulator on the driver's side fender. I went and bought a cheap gas pressure gauge and the mounting hardware, mounted it to the regulator, and ran a supply line to the carb. I then cranked it and found I was sending about 4.5 PSI of pressure... I dialed it back to just under 3. After that it still ran rich - I totally backed off the idle speed until there was no way for it to touch the cam. Then I adjusted the mix and while I could get it running okay, it was still running rich.

Finally, I pulled the plug off the vacuum line that comes out right above the EGR. I put a hose on there and cranked it up then pinched that line and found that if it got just a bit more air in there, it ran really well. So I ran it down to the charcoal canister and put a "T" on it - one to the vacuum switch port and one to the "dump" port. My thought was that doing this would make the canister "always on" and I would get the added benefit of a working canister for venting the float bowl and gas tank.

Re-adjusted the mix, drove it, re-adjusted...and I have made some small movements since to try to get rid of a slight miss at idle here and there - but it's a different car. No more gas smell, no more flooding out at red lights or stop-and-go traffic - no matter how long I sit (fifteen minutes yesterday), and no more flooding if I park it and walk into a store and come back out fifteen minutes later. I push the pedal in to open it up for air and it cranks right up then drops to idle. I am still trying to get the choke re-adjusted but I'm good with the way it runs now.

Oh - and my mileage went from 10.5 MPG to 14.5 MPG - so I think it's a good thing...

That's my story - maybe something in there will help or give you an idea.

Or maybe someone will come along and tell me I'm crazy for running a vacuum line to the canister like that... Who knows?

 

[uptillnow]

Here is a brief starting point for the Weber 38-DGES, we can correct from here. There are plenty of people who know about Weber's on this site.


IDLE Jets (both) .55mm
Main Jets 1.45mm
Air Jet 1.70mm


Idle Speed Screw in 1/2 turn
Mix screws out around 1 1/2 turns
Initial timing around 10 BTDC, then hook up manifold vacuum advance

 

[LeadfootCJ7]

Oh yes...Weber Carbs Direct... I dealt with them on a 32/36 last year and they are not well-versed technically. I ran their carb for about six weeks before Matt here recommended I call Tom at Redline and get a real Weber.

I got the 38 and I've had my own issues with it running rich (black exhaust, gas smell, flooding out in traffic or after parking for a bit...) but I spent some time working on it last weekend and I actually vocally threatened her with spending the $1K to grab a throttle body injection to install. Funny thing - She started to run better shortly thereafter. Not sure if it was the work, or the threat, LOL

What I did:

Before this past weekend, I had done many things but not changed any jets. Per Tom, my carb was jetted correctly for what I needed and he didn't want me to touch it. My last advice from him was to drill 1.25mm holes in each throttle plate to let in more air. I did this and while it made things better, it wasn't by much.

Honestly, I have a deal on a 6.0 LS I could swap in. I would spend $$$ on that before buying another weber just to get support. Sadly a new weber carb would cost more than the LS which makes it even harder to buy another carb just for support. I think Tom may be who I spoke to. I was a little disappointed in how the attitude changed once he determined I did not buy their authentic carb and bought a "rip-off". I was planning on buying some jets and such. I would assume I could have just ordered from him and they would have fit. I understand, but the significant change in tone was a bit much.

I will look into the charcoal canister. Mine is not hooked up, but I actually started looking at that last week. It wouldn't be much work and certainly won't hurt.

Here is a brief starting point for the Weber 38-DGES, we can correct from here. There are plenty of people who know about Weber's on this site.

IDLE Jets (both) .55mm
Main Jets 1.45mm
Air Jet 1.70mm

Idle Speed Screw in 1/2 turn
Mix screws out around 1 1/2 turns
Initial timing around 10 BTDC, then hook up manifold vacuum advance

Thanks, I was leaning towards 55 or 60 for idle jets. It looks like that is the way to go.

 

[LeadfootCJ7]

Sooo, to make this more interesting I was reading through some threads on weber carbs here. From the ID information I do have a redline weber carb with the exception of my choke being the wrong color. The other castings look like Redline webers. How do I definitively tell? It did seem odd redline blew me off based on the color of the choke which could have easily been changed. It would be nice to know what I have and who I should look to for support.

 

[Hoover7]

Sorry for the long post, but I, too, have recently upgraded to the 38-DGES, and like several others on the forum (Tsanchez, Geek, and Kovac), had tremendous difficulty in establishing an idle at baseline settings. The initial configuration UTN lists above is exactly how I began, and good advice.

Like you (as well as others who have had issues), my 84 4.2l has been modified. I rebuilt the engine with 30 over pistons, have borla headers, and an aftermarket Crane mid to high RPM cam. As a result, the mods really seemed to impact on my fuel air ratio at idle (I know this now- but not when I began). I think the combination of longer duration times and open valve overlap (from the cam), coupled with the increased flow through the headers was pulling more air through the engine than a stock engine. Not sure what the 4.0 conversion would do, but suspicious that something similar is happening.

I started my adjustment process (truly, it is a process) at the above settings as per Tom’s advice at Redline. Furthermore, I also drilled 1mm holes in both throttle plates. The result? It was terrible- the exhaust was not just black, it was shooting out black carbon fuzzballs. And stinky? Smelled like a burning tire made of diesel. Somehow, I managed an idle speed of almost 200 RPMs with 12 degrees of advance, no vac advance. My final setting that evening before I had to detox were ¾ turn in on the idle speed screw, and around one turn out on both mix screws.

Needless to say, I was discouraged. But if I am anything, I’m determined. And I had help from Tom. Lots. Cannot say enough good things about his patience with my lack of knowledge (Hell, I’m a biologist) and his deliberate process. Went back in the days following and tried to recreate my initial results starting with the same parameters - No dice. Just could not get any response by adjusting the mix screws, and the engine would die before I could cover the enriching holes with the throttle plate.

But by chance, I had a ‘eureka’ moment. Well, more like an accidental ‘eureka’ moment. With the engine barely running (~250 rpms, spewing toxic exhaust), I tried to switch my vacuum gauge from the ported vac to the manifold vacuum and somehow dropped the manifold vac plug. The effect was amazing- engine rpms shot up to 900-1000 and the exhaust cleaned up substantially. With a wide open manifold port, no less. Well, of course, I decided to see if I could tune the carb with a wide open manifold port. Wow, what a difference- I was able to back off the idle speed screw < ½ turn in (ported vac solid 0), and the idle, for the very first time, became responsive while adjusting the mix screws. All because a ¼ inch diameter hole was bleeding air into the manifold.

After relaying all of this to Tom, he suggested that increasing the size of the holes in my throttle plate to 1/8 in would likely help. He also cautioned me about the potential ‘dieseling’ that might occur since air would still be able to move past the throttle plate at shut down (no issues with that yet).

Well, I was reluctant after comparing the 1mm drill bit to the 1/8in drill bit. No analogies here, but that’s a massive increase in size. And it’s really hard to put metal ‘back’ into a drilled hole. So I decided to walk it up in size slowly. I increased the diameter in four incremental stops, each time reinstalling the carb and trying to tune it using the best lean idle procedure. It took all day, but the results were worth it.

My carb now has two 1/8in holes in the throttle plate and I’m able to tune it effectively. I’m still tweaking my mech and vac advance timing, and may have to increase my idle jets to .60mm, but will know more about that after working on it this next weekend or two.

Again, our situations may be completely different, but with patience, determination, and an open mind, I’m betting you can get this weber to tune up for you. Again, apologies for the long post!
I’ll be following along! All the best-

Hoov.

 

[LeadfootCJ7]

So, I have some great news.

At Uptillnow's prodding I called redline back and dialed Tom's extension directly. He was not who I talked to before. Different voice than the guy I talked to before. Tom was very nice and knows a ton about these carbs.

The good news, I do indeed have an authentic weber carb. Back when I purchased my carb, WeberCarbsdirect bought their carbs from Redline with a water choke. They would then fit the electric choke on them and sell them as a DGES. While my choke is not redline (I can live with that), my carb is indeed a quality Redline Weber. That makes me feel better. Apparently the newer WeberCarbsDirect carbs are made elsewhere.

Tom talked through some things with me including me getting some 55 jets as a good starting point as well as explained the difference in the way Weber CarbsDirect set the floats vs how redline does. He said that alone make the WeberCarbsDirect run very rich. I am going to order some jets and work on the float. I am thankful for Tom's knowledge and willingness to help. I am hopeful in a couple weeks my Jeep will be running much better. As I make progress I will report the steps and results. I may need to look back in the future so I might as well document it somewhere.

 

[BagusJeep]

Good to hear you are progressing Lead.

I have done this conversion a number of times using LCN Made in Spain Weber 38 DGMS and never had these problems. I have been very pedantic about adapter plate flatness and sealing and set it up as per the instructions in the box with 55 idle jets and the butterflies completely shut but apart from that have not had an issue.

I had a look in my very old Weber book at the idle circuit.

If the jets are right and all vacuum leaks are sealed then the only way for air to enter is through a poorly seated butterfly valve (or one cracked open or drilled) or the calibrated bush/hole in the venturi above the butterfly that then mixes with the fuel in the idle circuit just below the idle jet, emulsifying the air and fuel together. See below cutaway diagram of the carb, you will see the holes i am referring to.

This bush/hole is not adjustable by us mere mortals but is the constriction that governs the air entering the idle circuit. With a very small hole not enough air means it will not idle very high, whereas if slightly the wrong size may well lead to rich or lean running for a 55 jet size but you can change the jet size to get it just right.

Perhaps this is why Redline recommend drilling a hole in the butterfly, this bush/hole is too small or blocked and you would struggle to alter it yourself. I would be surprised, it is supposed to be a calibrated hole. ( I must remember that term!!)

One problem with poor idle quality (not low idle per se) that does sometimes crop up in dual venturi carbs is that the butterflies are not closing properly, either due to machining or the gears on the side which synchronize the butterflies. If it is synchronisation, it is usually the secondary that is not closing fully.

If the idle speed screw is wound out far enough to stop touching the linkage and your idle mixture screw is in, the engine should die (no air or fuel source). If not then possibly only one throat is drawing fuel, almost always the secondary. This can be verified by opening or closing the fuel mix screw on that particular throat and the engine will respond quickly. I think (and perhaps the experts can correct me) it can be corrected with the slotted screw on the right hand qadrant in the pic below which will change the relationship of the gears to the primary throttle shaft.

I have not tried listening to the butterflies but you may be able to pick up a hiss if you use a plastic tube and out the end near the butterfly sealing surface. Any hiss is undesirable on a closed butterfly.

If it is one or both venturis it could also be because the butterflies are not sealing due to a machining issue or you have drilled a hole in it. If a machining issue, it is going to require a specialist as they sit at about a 7.5 degree angle when closed with a finely machined edge.

Hope that makes sense, carbs are great tech. These Made in Spain LCN Weber carbs are neat but when I look at my older Italian Webers, they are just not as finely machined (Think Seat v Alfa Romeo, you knew when you had an Alfa Romeo that the carbs were the best).

 

[John Strenk]

You could drill out the "calibrated holes" in the carb. I remember doing that on a wildly modified X-19 I worked on.

But then some also had a convent air correction jet (44).

I think my 45 DCOE had these on them. No need to drill holes in the throttle plates.

How common are holes in the throttle plates?

Here is a Stock BBD of a Chrysler 318

This carb came from the factory with the holes drilled into the throttle plates.
Probably to overcome the tons of emission stuff load on the engine.

 

[uptillnow]

Weber on some models, IDF, IDA, DCOE, DCNF etc all had air by-pass valves built into them.


The Weber carbs we deal with on Jeeps are 32/36 DGEV and 38-DGES do not have the air by-pass valves.


Therefore (as a last resort in tuning) we drill by-pass air holes in the throttle plates to increase the idle speed, YET keeping the leading edge of the throttle plate at or below the enriching/progression holes, at the maximum allowed 38-DGES = 1/2 turn in, 32/36-DGEV = 1 1/2 turns in.


This is not uncommon, I just use it as a last resort, like with a 258 with a 5500 to 7000 RPM cam in it, or worn out timing chain and gears with retarded cam timing.

 

[John Strenk]

There is always the 1963 230 ci SOHC Tornado found in some jeeps south of the border or "Super Hurricane"

Not bad for a 6 lobe overhead cam. Yes 6 lobe...

Some racing versions of these motors put out 350 HP
yes it's a hemi. Good old Toledo Iron.
https://en.wikipedia.org/wiki/Jeep_Tornado_engine

 

[LeadfootCJ7]

Well, parts came on Monday (faster than expected). I got a chance to swap the jets last night and run it for a few minutes. It seems better, but still a tad rich. I am going to try to work on it some this afternoon. It feels good to be heading the right direction. I am putting it on a trailer tomorrow afternoon because I am heading to a buddies farm Friday morning for a weekend of light wheeling and target practice. It already runs better so that will be nice. I am hoping to see how good I can get it before the weekend and then make adjustments after the weekend.