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School me on Webers - plz

Turbo Dog

Well-Known Member
Howdy all, new to vw engines and Weber carbs, but not new to engines and carbs. I've built and worked on mostly American 4 barrel styles and Bing carbs. I've ordered the Haynes Weber manual but it hasn't arrived yet. I brought this engine up from sea level to it's new home at 7400 ft. It definitely needs to be re-jetted and currently has a 52 in what I think is the main jet (#5). I can make it idle using what I think are the idle fuel adjusters, the big spring loaded screws at the base.

My guesses are:
#1 - ??? didn't touch them yet
#2 - ??? looked like a plugged hole
#3 - ??? why only on one side?
#4 - Needle and seat?
#5 - main jet
#6 - idle speed

Are their some model Identification numbers hidden somewhere?

Then there are two on the back side by the fan tin work that I couldn't take a picture of. Any help is greatly appreciated.

The engine also has headers with a super trap...what's a good muffler to tame down the sound without going silent with too much back pressure?

Thanks
 

green787

Well-Known Member
Are they down draft, side draft??? What is the DCOE number or something close to that.... Yes the big spring loaded screw at the base of the carb is the air/fuel mixture screw... Don't tighten it down too tight or you'll blow a hole through with the needle and it will never idle... 1 1/2 turns out initially.... Turbo mufflers at any parts house...
 

Turbo Dog

Well-Known Member
Looks like I forgot to put up the picture with all the screws numbered. Its a single down draft carb but I didn't see any nnumbers on it. Think I already fpund out that #5 near the top is an air jet, and them mains are down in the throat. I'll put that pic up soon.

Thanks for the muffler recommendation
 

green787

Well-Known Member
The main jet is at the bottom of the float bowl... It is prone to getting a grain of silica sand in there that will cause confusion during trouble shooting.... Carefully remove the top of the carb and look at the bottom of the float bowl with a flashlight to see if there is debri in the main jet...
 

Turbo Dog

Well-Known Member
Okay, I'll get to that in a few days, I need to know what jets are in it now.

Finally found some numbers on the rear of the driver'side base flange.
by LON (CE)
 

partybarge_pilot

Well-Known Member
Fortunately you are not in Komifornia. The biggest problem with Webbers currently is ethanol. If you don't drive this every day, only run strait gas in it.
 

Turbo Dog

Well-Known Member
Okay here is the picture that goes with my numbers. There are also two more adjustable screws with lock nuts on the other side of the carb next to the fan shroud. I don't know what they do.

My guesses are:
#1 - ??? didn't touch them yet
#2 - ??? looked like a plugged hole
#3 - ??? why only on one side?
#4 - Needle and seat?
#5 - Idle air jet
#6 - Idle speed
upload_2017-3-12_13-31-56.png
 

Turbo Dog

Well-Known Member
Found a diagram with some help from my cuz...so are these descriptions right?
#1 Air bypass...guess that's used to balance the flow from the two sides
#2 Post throttle plate vacuum port - where I could hook up a manometer to balace the two sides
#3 Pre throttle vacuum port for a distributor advance
#4 part of the fuel inlet, looks like the needle and seat are internal
#5 Idle air bleed - Does that allow a wider range of adjustment for the idle mixture screws?
#6 Idle speed

The engine isn't running poorly other than being too rich after bringing it up from sea level to 7400 ft. It ran fine on the test drive at sea level.
 

Turbo Dog

Well-Known Member
Okay, as soon as I pull the top of the carb off it starts snowing again, not a problem for most of you. I had waited until it stopped, just a small spring snow to help the pastures around here grow.

I couldn't find a numder on the jet, the outside of it is covered with a hard black layer, not sure what that is from.

Can't figure out how to put up a picture of it while I'm on a phone.
 

Turbo Dog

Well-Known Member
Put the top back on, then the snow stopped again, so off it came again. The black stuff came off easily with a hand held wire brush. The jet in the bottom of the bowl that I think would be for idle is a #55. The main is a #140 on the end of an emulsion tube marked F7 with a #50 air corrector jet in the tube. Their is a 32 hand engraved in the throat of each barrel, so I'm guessing that they are 32mm venturis.

Looking at pictures I think it's an IDF because of the way the emulsion tube stand up tall out of the top.

Looking on carburetion.com they have a jet kit with mains sized 110, 120, 125, 130 and it is for 28-32mm venture carbs on engines up to 2000 cc, mine is an 1835.
737-240 - Carburetors Unlimited

Is this IDF update kit worth anything from CB Performance?
6457 Weber IDF Update Kit - fits 44mm IDF (2 carburetors)
 

JEFFRPM

Non Sugar Coated
If you think you know webber carbs I'd like to meet you because your fictional like the Easter bunny or Santa.
 

JEFFRPM

Non Sugar Coated
Post counts don't matter to me just bored, besides I care about human life & mental stability, learning webers, parts, jets, air bleeds, emulsion tubes, needle & seats, air horns, synchronizing, EVERYTHING about them you will understand trust me. May I suggest you or a loved one have the local suicide hotline number handy.
 

_

Well-Known Member
Start Here....

REDLINE - Serving the U.S., Canada, Central and South America for over 30 years

They should be able to answer all your questions. My guess, 1-2 sizes smaller on the main and you'll be OK, provided the motor was tuned correctly in the past. Again, if the motor was originally tuned properly with these carbs, there should be no need to change the air jets or emulation tubes. The idle jet size can be compensated for with the Idle mixture screws.

In addition, item #4 in your pic is where the carburetor filter is located, not the needle and seat location. The needle and seat is on the bottom side of the carb cover. If you have not removed this threaded brass cap which retains the filter, do so and inspect the filter condition. Note, as old as these carbs are, the paper gasket may crumble when you remove the brass cap over the filter. Be sure to have a knew gasket for reassembly. You may wish to change the needle and seat also. These seats have a size written on them (orifice size), be sure to replace with the same size needle and seat. And, do not forget to install the aluminum sealing washer when you thread in the new seat. You should be able to use the old washer as they typically do not get damaged.

If you can't get answers to your questions, I have contact information to the gentleman who started Redline Weber. He has probably forgotten more about Webers than most persons will ever know.

The link you posted for the Weber IDF update kit,if it were me, I would not consider it. I did a lot of work with Webers in the 80's and for the most part, Weber did it right the first time. Yes, there are several improvements which can be made, but not without access to a dyno. We made our own chokes, primary venturi(s) in addition to annular venturi(s)/chokes. If you don't have an experienced Weber tuner in addition to a dyno, leave all as stock or you will forever struggle to get the motor to run properly again. Last, if you wish to make improvements without cost, remove the primary venturi(s) and the chokes, and sand away all the casting flaws followed by polishing the surfaces. Be careful not to reshape either while doing so. Last, find yourself a set of large radius, fully rolled air-horns. You may have to make these yourself.

Good Luck.......
 
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JEFFRPM

Non Sugar Coated
Good luck

Performance parts in wyoming are at best hard to find add in the "weber" thing now you really going to have fun then add in a altitude change you start all over. Not to be negative your going to get educated and will get to know the UPS Driver personally.
 

Turbo Dog

Well-Known Member


Update: Thanks for the help from ProFORMANCE

#1 Air bypass...guess that's used to balance the flow from the two sides
#2 Post throttle plate vacuum port - where I could hook up a manometer to balace the two sides
#3 Pre throttle vacuum port for a distributor advance
#4 Fuel filter
#5 Idle air bleed - Does that allow a wider range of adjustment for the idle mixture screws?
#6 Idle speed

I sent some carb pictures to Redline and he identified the carb as an IDF, now I just need to measure the throttle bore to know which one it is. I ordered a universal rebuild kit, a jet kit, and an O2 bung. I don't have a dyno but I do have an O2 readout and that will work for evaluating how the tuning is doing while driving. I have a Testo 350 I use at work and can use it if needed for more precise measurements.

I read the Weber Carburetors book by Vernon P. Braden, the theory of operation section got me up to speed with what all the parts are doing. I have to rebuild an old Bing carb this weekend then my parts will be in and I look forward to tuning the Weber.
 

Turbo Dog

Well-Known Member
I got my carb gaskets and jet kit, along with a fresh battery not shown here. Gonna have some fun changing the jets out tonight. Probably just go two steps leaner to start with. I am waiting on some weld on O2 bungs to arrive, then I can install my AFR readout. Also waiting on a 10" turbo muffler with a spark arrestor to arrive and be installed before the final tuning will happen.
upload_2017-3-29_17-29-8.png
 

Turbo Dog

Well-Known Member
Just found that the air corrector jets in the emulsion tube have had a chamfer cut into the top of them. Is that a common modification? All the new ones in my jet kit are square across the top.
 

green787

Well-Known Member
Just found that the air corrector jets in the emulsion tube have had a chamfer cut into the top of them. Is that a common modification? All the new ones in my jet kit are square across the top.
It probably won't make much difference as long as they fit and the threads are the same...
 

_

Well-Known Member
Depending on the size of the chamfer. If I recall correctly, back when I was involved with Webers, we had air jets with small chamfers and air jets with no chamfer, all of equal size. It may have been nothing more than the manufacturing process. Or, there may be something to it that I have no experience with, if its a large chamfer.
 
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