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Discussion Starter · #1 · (Edited)
I thought we might get a thread going where we could all share and maybe cover some of the basics and what appear to be the most common challenges that we face when installing a Weber and hopefully get some good discussion going.

This thread will begin with a more focused view on the initial set up, the importance of the base-line settings and general discussion of a Redline Weber carburetor and not really intended to be a troubleshooting guide. It's rather an offering to a trouble free installation and use thread.

Size Selection

Set up correctly, either the 32/36 DGV or the 38 DGS should provide great performance and mileage on the 4.2 or even the 2.5. I've just been tickled pink with my 38 and I know others who love their 32/36 DGV.

Here's a good link, should you still be deciding which carb will work best for your application.

Making The Right Choice 32 or 36

Adaptor Plates:

The adaptor plates need a close inspection and possibly attention prior to assembly to avoid problems with vacuum leaks. They are often delivered with uneven mating surfaces, casting flash and just about any number of abnormalities that you can think of.

It is well worth your time to give them a close inspection before the install. By using a straight edge over the entire mating surface of each side of the adaptor plates, you'll be able to tell if the surface is flat. They sometimes need some sort of work in this area and some filing and sanding may be needed to ensure a flat surface. Should the plate need some work to flatten out, you can place a sheet of wet/dry sandpaper on a flat surface, oil it and sand away any high spots.

Once the adaptor plates have a good, flat surface to work with, you can go ahead with the assembly of the plates. It's a good idea to lightly coat some wheel bearing grease over both sides of the mounting gaskets to ensure a good seal. You may want to perform a test assembly to make sure the mounting bolts are long enough. I've seen kits that actually required a trip to the fastener store for bolts that were a touch longer than the ones supplied.

Once the plates are secured to the manifold, you can thread the carb studs into the top plate. This is a part of the initial assembly where some mistakes can be made. If the studs are actually tightened down, they will serve to pry the adaptor plates apart and cause an air leak. Rather than tightening the studs down, simply coat the threads with red Loc-Tite, screw them down until they just make contact with the lower plate, back them out 1/8th turn and walk away until the Loc-Tite has set.

A little Teflon tape on the threads of the PCV port and you should be good to go with the adaptor plate assembly.

Curb Idle Throttle Plate Position

Here's where the vast majority of complaints and confusions arise when it comes to setting up a Weber.

When installing either of the Redline Weber conversions, I suggest the first thing you do is to flip the carb upside down and determine the maximum amount that the throttle plate can be opened for a proper curb idle throttle plate position.

To do this, you'll need to use your fingers or maybe insert a short piece of 3/8 tubing between the air horn and the choke plate to hold the choke plate open while you move the throttle from idle to wide open. You should hear a 'click' as the fast-idle cam loses contact with the fast idle screw and the throttle plates should return freely to their fully-closed position. This is actually my preferred method of holding the choke plate open so you can set the throttle plates...



Yes, that's actually a short length of toilet paper roll. I mean, who can't find one of those in a pinch :teehee:

From there, use a screwdriver to unscrew (counter-clockwise) the idle speed adjustment screw to the point where it loses contact with the linkage. Then, from the point that the idle speed adjustment screw just makes contact with the linkage, slowly turn the adjustment screw in (clockwise), counting in at least 1/8th turn increments, until just the very outer edge of the first progression hole is exposed and take note of how many turns were required to get there. On the 32/36 DGV, the plate should be just shy of uncovering the edge of the "S" port, which will be a much smaller port off to the side of the larger progression port. Notice how this is illustrated in this photo, it should look similar to a crescent moon, something like this...



This screw setting, what ever it may be, is considered your absolute maximum idle speed screw adjustment and can not be exceeded when tuning otherwise your performance and mileage will surely suffer.



This photo shows just how much of the progression hole is exposed with the idle speed screw turned in only ¾ of a turn. It's easy to think that a ¼ turn doesn't really mean much but it makes a big difference, as you can see. This is why Redline so strongly emphasizes the importance of the idle speed screw setting.

For a Weber 32/36, this screw setting should be no more than 1 ½ turns in. For a Weber 38, it will be no more than a ½ turn in. When this screw setting is exceeded, the engine will pull from the progression circuit rather than the idle circuit and will likely have a rich or stinky idle and the engine will often not even respond when the mixture screw(s) are adjusted. This is an indication that a larger idle jet is needed. Conventional wisdom might suggest that "it's rich so I need smaller jets." That, however, isn't the case.

This maximum setting is crucial and a properly sized idle jet will allow your engine to idle without exceeding the above mentioned screw settings.

There are plenty of topics to discuss here like float level, lean-best idle, idle jet size, fuel pressure, ignition requirements, etc. and I know there are some really sharp Weber guys on the forum so hopefully we'll get some great discussion on here.

Shawn
 

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This photo shows just how much of the progression hole is exposed with the idle speed screw turned in only ¾ of a turn. It's easy to think that a ¼ turn doesn't really mean much but it makes a big difference, as you can see. This is why Redline so strongly emphasizes the importance of the idle speed screw setting.
Shawn
Thank you Shawn....
The success that I have experienced tuning Weber carburetors has come from this enrichening hole not being exposed adding tooo much fuel at idle. Not exceeding the MAXIMUM idle speed screw setting and/or ZERO vacuum at the "S" or distributor ported vacuum advance. This point seems to be the "trick" when setting up a Weber.
Thanks
UPTILLNOW
 

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Not exposing the enrichening/progession circuit hole makes sense, however...

Isn't the 32/36 supposed to be a 'modification' to a 258? If so, then why in the world do so many people have issues with the Weber being supposedly jetted too lean :thumbdown: (according to the Weber instructions)?

Example: I've heard of many people who have their baseline funamentals perfect (timing, no vacuum leaks, fuel pressure fine), but CANNOT get the 32/26 to idle until the mixture screw is anywhere from 3-5 turns out.
 

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Discussion Starter · #4 ·
Not exposing the enrichening/progession circuit hole makes sense, however...

Isn't the 32/36 supposed to be a 'modification' to a 258? If so, then why in the world do so many people have issues with the Weber being supposedly jetted too lean :thumbdown: (according to the Weber instructions)?

Example: I've heard of many people who have their baseline funamentals perfect (timing, no vacuum leaks, fuel pressure fine), but CANNOT get the 32/26 to idle until the mixture screw is anywhere from 3-5 turns out.
The 32/36 can be a 'modification' to a 258 but we have to remember that it was originally designed for a 2.5 liter engine, not a 4.2.

This increased demand that's placed on the idle circuit by its installation on an engine that's double the size for its originally designed and intended use can wreak havoc on a less-experienced tuner.

Like the Redline set-up documents say, if the idle speed screw setting isn't exceeded, a mixture screw setting of more than 2.5 turns out on a 32/36 DGV is a strong indication that a larger idle jet is needed on the primary side.

Redline assembles these carbs with a good, average-use idle jet and then supplies the screw setting absolutes and procedure to help the end user determine if a larger or smaller idle jet is needed for his particular application.

Shawn
 

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What I'm referring to is not the carb itself, but Weber's entire conversion kit.

I noticed that there are multiple conversion kits with the 32/36 on Weber's website, two of which are not intended for the 4.2. I wonder if some dummy just found a random carb & threw it on, because mine is a slug.

I have not pulled my jets to see what sizes they are yet.
 

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Hey Shawn...good topic.

I'm still trying to get my 32/36 "right" with McMud's and your assistance. You guys have been very helpful and more than patient with me and I appreciate that.

I'm whittling things down and right now my biggest issue is I can't get it to idle smoothly. It 'wanders' between 400 and 1K rpm. If I cup my hand over it, the idle picks up and smooths out. McMud explained that doing that is just like choking it.

Any suggestions?
 

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Not exposing the enrichening/progession circuit hole makes sense, however...

Isn't the 32/36 supposed to be a 'modification' to a 258? If so, then why in the world do so many people have issues with the Weber being supposedly jetted too lean :thumbdown: (according to the Weber instructions)?

Example: I've heard of many people who have their baseline funamentals perfect (timing, no vacuum leaks, fuel pressure fine), but CANNOT get the 32/26 to idle until the mixture screw is anywhere from 3-5 turns out.
I know the REDLINE conversion kit comes with "various" modifications. The jetting that they supply functions very well "when" the tuning procedures are followed. The jets they use are a 75 pri idle jet, a 60 sec idle jet 145 main jets and 170 pri air jet and 160 sec air jet. Typically the problems come when we don't have this base line jetting and or vacuum leaks. Check to see what jets you have, then the set-up (speed screw, idle screw settings) and let us know what you find. There are many VERY knowledgeable tuners on this forum who will be more than happy to jump in and tell you everything they know.
UPTILLNOW
 

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ok, i've got some great feedback from swatson, but i need one more question answered. i was looking to order some jets based on feedback from clifford performance guys. itold them my set up and my intention to stick w/ the 38 weber over the 32/36( i have both ). the guy i talked to told me b4 i even consider changing jets, to get a redline large diaphram fuel regulator. he said the holley low pressure ( which i have ), mr gasket, or other small diaphram regulators are probably a main source of my frustration. he said it will give me the flat spots that i told him about. my concern was that i still may need to up my idle jet based on threads about rich/ stinky smell that wont go away w/ adjusting the mix. is this a sale pitch, or is there truth to the regulator?!?
 

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Well, as swatson454 originally posted, I found 'the spot' in my idle speed screw where the progressive port is exposed. I did not pull the carb from the manifold, but....

Long story short, I couldn't get it to idle right, even with the idle speed screw in quite a few turns.

After sloooowly turning in the idle mixture screw (until it was about 2-2.5 turns in - recommended setting), I unscrewed the idle speed screw, and VOILA! She started purring like a kitten.

Good information, swatson454!
 

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GPS....maybe we are on the same wavelength. I went through everything (including setting float levels) again, and I too hit the "sweet spot". My idle was little low so I dialed in 2" of vac with the speed screw...now it idles great and it pulls even better.

A major improvement is to swap in a '79 dizzy if you've Nuttered. Gives you 2x mechanical (centrifigal) advance.

Swatson....thanks for all your help!! I appreciate it!!
 

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Discussion Starter · #13 · (Edited)
Thanks guys!

Like uptillnow said, the throttle plate position is the trick to setting these up and everything you do to tune the carb will stem from there.

Now that you've found the 'sweet spot' and you know the enrichment holes aren't exposed, you can use the mixture screw setting at lean-best idle to determine whether a larger or smaller idle jet can be used to find improvements in either power or fuel economy.

I'm very pleased that the information has been useful. Thanks for your input!

Shawn

Edit: I forgot to answer an important question from usa.

I don't have a problem running regulators, per se. My main concern is running the $30 units. If your luck is anything like mine, if there was one faulty unit that made it through the production line, that's the one I'm taking home with me and there are a lot of faulty units with those things. Setting them at 3 psi in the driveway is a different scenario than driving up a long grade and, unless you have a pressure gauge mounted in the cab, it can be a whole bunch of fun figuring out what the heck it's doing and when.

You seem to have two options with a Weber and personally, I prefer the $14 upgraded Viton-tipped needle valve. That valve will handle all of the fuel pressure that your stock pump will deliver. The other is to run a regulator but reliable ones can get expensive. I ended up dropping over a hundred bucks on a Barry Grant bypass unit on a 383 because I was sick of struggling with the cheaper units.
 

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How about some general terms and definitions:

When you look down the throat of the carb (engine off) and have someone press on the gas, do both of the butterflies open at the same time (Weber 38/38), or does the passenger side open 2/3 of the way before the driver side starts to open (progressive) (Weber 34/34 and 32/36).

The terms DGV, DGEV, DGAV: D is down draft, G is the mounting direction, V is manual choke, EV is electric choke, AV is water choke...

In addition, on the 32/36 progressive carburetors, there is an overlooked adjustment that is recommended in the Weber rebuild manual to prevent a stumble when the secondary is opened. Basically, you need a small amount of vacuum or you will stumble when the secondary opens (IIRC the manual calls for 0.05mm opening and I was told by the guys at carbsunlimited to open it 1/6 turn or so) ...and if it is open too much you pull fuel from there during idle...

The secondary is the side that stays closed until 3/4 throttle (or there abouts) and then opens up. If you follow the linkage over (remember this is the barrel closest to the master cylinder) you can see where the linkage hits the "stop". This is the underside of an adjustment screw (flat head) that can be used to adjust the resting place of the secondary linkage. Back this screw off until the linkage no longer touches it (secondary throttle plate fully closed). Then advance the screw approximately 1/6 to 1/4 turn in from first contact with the linkage. This will allow a small vacuum to be pulled through the butterfly (to prevent vacuum stumble); but, not enough vacuum to affect the idle circuit.
 

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ok, i've got some great feedback from swatson, but i need one more question answered. i was looking to order some jets based on feedback from clifford performance guys. itold them my set up and my intention to stick w/ the 38 weber over the 32/36( i have both ). the guy i talked to told me b4 i even consider changing jets, to get a redline large diaphram fuel regulator. he said the holley low pressure ( which i have ), mr gasket, or other small diaphram regulators are probably a main source of my frustration. he said it will give me the flat spots that i told him about. my concern was that i still may need to up my idle jet based on threads about rich/ stinky smell that wont go away w/ adjusting the mix. is this a sale pitch, or is there truth to the regulator?!?
My experience using a Clifford manifold is; the large plenum under the carburetor slows the velocity of the already mixed air/fuel. This low RPM and slower velocity unfortunately is where the Jeep engine makes all of its great torque. I like the stock Jeep manifold, it works better than any aftermarket manifold. When Clifford sells a 38-DGES with one of their manifolds, the carburetor needs to have it's float set and jetted for a Jeep engine. When you smell that gassy unburned stinky rich fuel smell, is from the idle jet being too small and the throttle plates or idle speed screw being turned in more than ½. What happens is you expose the enrichening holes by opening the throttle plates toooo far, that draws raw fuel at idle. When you close the throttle plates you NEED to have enough fuel from the idle jet to run the engine. With a Clifford manifold, 55mm idle jets are a good beginning and may wind up at 60 idle jets.
As far as a fuel pressure regulator…. IF: 1. you are using the fuel return line back to the tank and 2. use a stock fuel pump and 3. you install an aftermarket "VITON" needle and seat YOU DO NOT NEED A FUEL PRESSURE REGULATOR… The use of anyone's regulator restricts the flow, volume and reliability of your fuel system. I DO NOT USE A PRESSURE REGULATOR WHEN I FOLLOW THE ABOVE SPECIFICATIONS.
UPTILLNOW.
 

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This is good work Shawn, I applaud you in you're attempt to head off many of the typical woes that surface soon after a haste makes waste install.

Knowing that you've devoted a great amount of study along with testing I'm looking forward to reading more.
 

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Discussion Starter · #18 · (Edited)
Lean-Best Idle

Now that we've had some good discussion on the importance of the throttle shaft's position and the carb has been mounted in a manner that will prevent an air leak, we can move on to setting the mixture screws and using their position to determine a suitable idle jet size.

With the 38 DGES, I like to turn both mixture screws in clockwise until they lightly seat and back them out two turns for my starting point. Start the engine and let it warm up, making sure the choke is fully opened. We're looking for the smoothest running engine speed that we can obtain without using the idle speed screw. Begin adjusting the mixture screws inward in ¼ turn increments, one then the other, then wait a few seconds and listen to the engine respond. 1/8th turn increments are fine, just remember to keep track of where you are. I often find it helpful to run a fast idle for a few seconds after each adjustment and then let the engine return to idle. The idle speed should begin to pick up and the engine smooth out. Keep going in this fashion until the adjustments do very little to nothing and then it actually starts to slow down or sound worse. Stop there. Now slowly back them out in 1/8th turn increments to the point where the engine sounded the best. This is considered to be the lean-best idle. Then, just make a note of how many turns out you are from its seated position.

If, at this point, you find the idle speed to be higher than you like, you can lower the idle speed screw to your desired setting, run through the mixture adjustment procedure again and be done.

If you found that the engine picked up by turning the mixture screws outwards, rather than inwards, beyond two turns on a 38 DGES, a larger idle jet will most likely be needed. A good quality idle speed found just less than 2 turns would be a good indication of an idle jet size that will provide you with good mileage.

For a 32/36 DGEV, lean-best idle being found at or near 2.5 turns out on the mixture screw means that the current primary idle jet size will likely provide you with good fuel economy. Beyond that though, is a pretty strong indication that an increase in idle jet size is needed on the primary side.

Selecting an idle jet where the lean-best idle is found with the mixture screw in the 1 3/4 turns out range on a 32/36 DGEV progressive and roughly 1 turn out on a 38 DGES will likely provide more performance and acceleration but could come at the cost of some fuel mileage.

Although it isn't very common, it is possible to need smaller idle jets. The first indication of this will be a lean-best idle coming with usually less than a full turn out on the mixture screws on the 38 DGES and about 1.5 turns out for the 32/36 DGEV. All of this assumes that the Maximum Idle Speed Screw setting has not been exceeded and that you still have zero vacuum at the vacuum advance or "S" port.

Most of these settings have been taken from Redline Weber's installation instructions.

Great discussion, guys. Thanks for everyone's input.

Shawn
 

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Shawn this is great stuff here….
This is also where a lot of things come into effect as far as sensitivity of the mixture screw and idle speed. First and foremost… From here on, I agree, we must assume that the Maximum Idle Speed Screw setting has not been exceeded and that you still have zero vacuum at the vacuum advance or ”S” or ported vacuum source, as discussed earlier. This is the basis for finding the “Lean Best Idle”.
REDLINE’s tuning instructions is looking for the “Lean Best Idle” with the 38-DGES = 1 turn out and with the 32/36-DGEV = 2 turns out. The size of the idle jets used to achieve these settings, as you know so well using a wide band O2 sensor, is ever so slightly on the rich side. Using these slightly rich jets usually over comes some vacuum leaks, various oxygenated and ethanol added types of fuels throughout the world. I have found that the “Lean Best Idle” can be found using the 38-DGES around 1 ½- 1 ¾ turns out with a 50mm idle jets, and on the 32/36-DGEV around 2 ¼ turns out with a 75mm idle jet. This is what I have found working well.
Some of the preferences of the tuners regarding the timing varies from manifold vacuum advancing at idle around 20 degrees BTDC and then retarding to a more “normal” timing on acceleration, and the “nutter” by pass using ported vacuum advance with the initial advance at around 8 degrees at idle, then the “stock” distributor without any ignition modifications around 10-14 degrees advanced. I bring these multiple option timing issue up because, there are many timing variations and the throttle plate at curb idle is must still be below the enrichening holes with ZERO vacuum at the “S” ported vacuum source and these initial timings will absolutely effect the curb idle speed and the sensitivity of the mixture screw and when starting the engine when hot. I guess you could continue leaning out the idle circuit until you hit a flat spot, then you need to add more fuel at the idle circuit or add more main jet fuel tipping in sooner and richer. Either way, fuel needs to cover up the lean spot.
Keep up this good work, I hope we can hear from others who can add too your great topic.
UPTILLNOW
 

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A time for all things... is how I see it with regard to the mix screw(s).
While adhering to the Redline Weber guide line screws settings as the basis for a rock-solid curb idle speed, we are actually gauging the progressive's primary idle jet or both idle jets in the synchronous Weber.

We are expecting a hesitation free ride. They did the testing for us so that we may rest assured, while using those standards, that those jets sizes are appropriate to provide adequate mix throughout the low speed circuit.

During that phase, while some allowance must be given to the accelerator pump stroke while using a mild/conservative acceleration, and then depending on which Weber you've chosen, the run-on fuel mixture is flowing through two enrichment holes plus the idle mix hole in the 32/36DGV or six enrichment holes plus the two idle mixture holes with the 38DGS, from two idle jets.


This is the flow capability that you are actually gauging at the published curb idle speed screw(s) setting.

When given the fact that most all of your everyday driving is on this circuit, it should be evident how vitally important it is to fit your carb with idle jets which will fulfill the demand.

Trust the Redline guide... adhere to each and every point made on it, they not only want you satisfied but they publish that guide so that every user may have awareness of the full potential of the Redline Weber conversion carburetor.

During the lean best setting you must be patient, allowing adequate time between each turn of the screw for the engine to react to the subtle change that would be expected in the flow rate.

You will be looking to draw down the flow to the point that a lean misfire is obvious and rather constant, then back the mix screw out (this is where I would suggest that an 1/8th turn is used) so that the lean misfire all but disappears. Once you hear that occasional lean hiccup at say every 15-20 seconds you are at the point which is considered the Lean Best setting.

I encourage you not to go any further out with that screw in an attempt to gain the highest idle or even what might be the smoothest curb idle speed. That point of adjustment should be considered a Rich Best setting. This one will cost you the fuel economy that the carburetor was designed to offer.

During that process have the air filter mounted in place after having filter oil applied to it.
 
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