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Sat Nov 04, 2006 7:52 pm

In response to a PM I have written up how I tune these carbs. From the little I've read here on TheSamba I am appearently one of the few (?) to make this carb perform on an air cooled engine. As I posted in one thread, I've not had any trouble with this carb that I didn't incur on myself. It may not be the carb of choice to get the most HP out of any given engine, but it's manners are very nice & once tuned properly yields superior drivability.

THE thing to keep in mind is that you are running on the Idle Jet to about 3500 RPM. So these are MUCH more important than the main jets to most air coolers.
The second thing to keep in mind is that DGV's, like all Weber Carbs, do not like fuel pressures over 4 psi.

These are my notes from a years ago Hot VW's article on tuning these carbs:

0) Set ignition dwell & timing first.

1) Idle Speed Screw: 1 turn open from *just* touching the tab

2) Idle Volume Screw (sometimes wrongly called the "Idle Mixture screw"): 2 turns out from LIGHTLY bottomed.

3) Start Engine

4) Adjust Idle Volume to highest idle speed while counting the turns or partial turns from the lightly bottomed position. Btwn 1-3/4 turns to 2-1/4 turns is where you want to be.
If more than 2-1/4 turns then Idle Jet is Lean - Increase jet size.
If less than 1-3/4 turns then Idle Jet is rich - Decrease Jet size.

5) Mains should start to drip out of the booster venturis at 3500 RPM
If the RPM is higher the Jets are too small. (See note on Air Corrector Jets)
If RPM is lower then the jets are too big. (See note on Air Corrector Jets)

Air Corrector Jets:
I do not have any simple way to tune these. They are modifiers of the range of the main jets & too a lesser degree the Idle jets. Air Jets have a progressively increasing (leaning) effect as the RPM's increase. And being that they are air jets, the larger they are the leaner the given mixture. It is possible to have two main jet & air jet combo's 'tip-in' at the same engine speed, and perform totally differently.
They can also be used, once your jetting is satisfactory, for altitude correction. There's a Rule Thumb that for every 2000 feet in altitude you can reduce the Air Corrector one size, but every engine will be a little different. Let experience by your guide here.

Emulsion Tubes:
They are located under the Air Corrector Jets. These are a black art. They are numbered in sequence of mfg, not progressively. An F4 preceeds an F5, but while an F4 might be nearly perfect for a 275 GT SWB Lusso V12 Ferrari, the F5 might have been developed for a 995cc Mini engine.
You will have to hope that the seller of your carb set it up with the correct Emulsion Tubes & leave them alone until you become an advanced Weber tuning guru.

Some Off Road specific notes:
If you live in an area where you can do away with the choke it behooves you to do so. The choke linkage is a dirt leakage path that is hard to totally seal off. I use regular J-B Weld for modifying carbs. The carb absolutely has to be clean for the J-B to stick. Over time the pressed-in plugs in the body can work loose. I put a dab of J-B on each and every plug, being sure to completely cover the plug and a little of the surrounding carb body. I use J-B to plug off all of the various ports & what-not associated with the removed choke.

And now the biggie, Float Bowl Vent mod:
The bowl vent, as delivered, is very suseptable to allowing slosh to enter the venturis. Which make the engine go really rich and blubber.
A note of caution on this mod: it is not a very complicated mod, but it does offer the opportunity to mangle the carb beyond use if not done right. If you need to be shown where the vents are, this is not a mod you should be doing. Proceed at own risk, I accept no responsibility for any mishaps.

The gambit is to block off the existing bowl vents with J-B Weld or a similar epoxy. Devcon Aluminum Putty works just as good and costs more. :)
I use a Dremel Tool to make a "socket" of sorts to locate a piece of 1/4" tube to be the new vent. I form this socket before filling the old vents with J-B as the socket needs to be in the same region as the existing bowl vents. I use masking tape across the bottom of the vents and fill them full or nearly so, and bond in the tube at the same time. Make sure that the epoxy can not get into the lower end of the tube or any hole that might be below the tube end.
I've always found that I could place the socket between the existing bowl vents, but is is possible that some carb tops or air filter adapters will require it to be offset towards one venturi or the other.
Usually the socket is at an angle and the tube has to be bent to extend straight up. I locate this bend such that the tube is centered fore/aft & side-to-side between the venturis. Keep in mind any air filter adapter clearence that you might need for the tube.
I've used .250" x .035" Stainless Steel tube and I've used 1/4" Bundy Tube (common fuel tube sold by auto parts stores). Either has worked fine, though the stainless tube should be roughed up below the bend prior to bonding on place.. Make the tube as long as you can. Note where the top of your air filter is. You can extend the tube clear up to within ~1/4" of the underside of the top.
An optional method is to use a short piece of tube and push a piece of fuel hose down over it once the epoxy has cured. If you go this route, do not allow any kinks in the hose.

Note that just occured to me that I'd omitted:
These carbs work best on an intake with two runners leading from the carb base. The intakes that have one big open hole are not worth messing with as they do not give the carb the kind of signal it needs.

Fri Apr 06, 2007 10:15 am

Thank you!!!!

I am trying to get one runing on the stock 1600 DP I just installed into my '64. All I was able to find everywhere else was the typical "throw it away, it's a piece of crap" typical of people that are not willing to spend the time (or have the know how) to get it right.

I am going to try to finish the tuning tonight, I will post how it turns out.

peaceout

dtroitj

Fri Apr 06, 2007 12:17 pm

Yeah, 90% of the people that posted that the 'Progressives suck' are just plain lazy. :wink:

I've seen few Progressives run as well as a stock carb. People seem to like that little 'kick' when the secondary opens up, though, which is the only reason I can think of that makes people want to run these.

I'm glad that NTSQD got his running good, though. He obviously spent some time on his.

But, in my opinion, if someone is looking for a performance gain, duals are the way to go. If someone wants driveability and low maintenance, stock is the way to go. Not really sure where the Progressive fits in here?

I've ran stock carbs. Single dual barrel downdrafts (Weber). Dual Single Barrell Downdrafts (Webers and Baby Dells) Dual double-barrel downdrafts (Weber IDF and Dell ), and also a few Progressives.

I'd never use a Progressive again, unless it's on a Toyota.

Fri Apr 06, 2007 4:36 pm

I was able to get stock driveablity (actually better than stock - at least compared to the stock engines I've had) with more torque & HP up top than anything stock.

DGV's are not the answer for everyone, but I contend that they are a good option for a mid displacement - mid HP level engine.
Once set up I've never had to mess with it again. Never had a plugged idle jet (how many synchronous 2 bbl owners can claim that?), never had to re-jet based on altitude or weather changes.

Sun Apr 29, 2007 10:40 am

going to use this info on my new rail

Sat May 12, 2007 5:55 am

well i read the post worked on the carb F'ed it up, reread the post did what you said and it works. so far i have it idleing good and i am going to start on the mains today . also how do you know if your pump jet is the right one (big/small) ?

Sat May 12, 2007 9:43 am

Here is a good web site on how to do things to a Weber Carb. Lots of good info.

http://www.racetep.com/webtechpage.html

Sat May 12, 2007 10:33 pm

Hey ntsqd, could you post a pic with circles and arrows and a little paragraph explaining how each screw is to be used? ie, which are volume/speed screws?

Sun May 13, 2007 12:13 am

they cant be that bad... :shock: can they.. :?

Sat Dec 29, 2007 12:20 am

i'm ditching mine and going for a centermount 40IDF

sorry guys :?

Sat Dec 29, 2007 7:08 am

you will make a lot more power with the 40. i like to cross post this info for people who are kind of stuck with the Progressive.

Sat Dec 29, 2007 6:41 pm

There was a forgotten step before "0"

Triple check your carb isn't worn out and needs a complete overhaul/rebuild.

I can't tell you the number of folks who try to get ancient leaky and wobbly carbs to run well.

Sun Dec 30, 2007 2:37 pm

mine spews a really acrid cloud of exhaust (burns my nose and brings a tear to my eye) and ive almost completely gotten rid of it but the smell of it is still there and smokes that nasty acrid smoke. could anyone explain this?

and no its not burning oil.

Sun Dec 30, 2007 9:28 pm

Thanks for posting this ntsqd. This info will help me ton this spring when I get my buggy back out. Stuff like this is what makes the Samba a great place!!

Sun Dec 30, 2007 10:13 pm

joe sounds like it still may be running rich or old gas. some times if gas is old it will not burn all the way and give you that smell.

Tue Jan 01, 2008 11:42 pm

vw505 wrote: joe sounds like it still may be running rich or old gas. some times if gas is old it will not burn all the way and give you that smell.

i was JUST thinking the same thing about the gas.

i had my tank removed..drained into a bucket (empty..but not sure of its previous contents) changed out the sending unit...reinstalled and gas re-used. ill run an Intravenous style test bottle w/ fresh gas and see if it works out.

but as far as my jetting goes. i have to turn the "volume" screw in about a full turn to get it to idle up...so go down a step on the idle jet?

60 so go to 55.

then what..repeat until i'm within 1 3/4 - 2 1/4?

Wed Jan 02, 2008 5:06 am

is this the webber progressive? if it is change the gas then start over. it sounds like you are on the rght track.

Idle Speed Screw: 1 turn open from *just* touching the tab.
thats the step i kept messing up , if you open it more you will see gas dripping out of the booster, you dont want that. one turn out thats it.

Wed Jan 02, 2008 12:16 pm

could i theoretically disconnect the linkage and turn the carb "the proper way" on the manifold to tune it. Then once i get it dialed in turn it the "VW" way?