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SGKent Premium Member
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PostPosted: Fri Dec 01, 2017 6:39 am    Post subject: Re: Carburator Reply with quote

dual advance meaning mechanical and vacuum? Make sure the right vacuum port is chosen, make sure the mechanical weights work smoothly, and make sure that the transition hole(s) are not exposed at idle but open as soon as the throttle is opened. The vacuum port to the distributor should also signal advance vacuum as soon as the engine starts to come up in RPM.

The old license plate - breadpan etc arrangements are novel and probably bring enough heat to stop or at least minimize icing. One could even lay some kind of aluminized heat insulator over the runners down to the case and secure it with something solid so it doesn't float away. That would help in winter. In summer one could reduce the amount of that blanket. Those who are not familiar with icing - it is caused by the drop in temperature across the venturi as the air expands and is combined with fuel much like an expansion valve in an air conditioner works to create the cold in an air conditioner. In certain temperatures and humidity combinations ice forms - even possible on 90F - 100F days.
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Wildthings
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PostPosted: Fri Dec 01, 2017 9:10 am    Post subject: Re: Carburator Reply with quote

orwell84 wrote:
I am interested in learning more about the power valve mod for the Weber progressive. One mod seems to involve blocking the vacuum passage which drives the power valve. The other, which involves routing a steel vacuum line from the vacuum port to the power valve I don't really understand.

Since I will need this vacuum port for the vac can on my distributor, I think blocking the vacuum passage to the power valve would be my best option, though I am still a little fuzzy on the details.

I am experiencing the off idle stumble common to this carb. It happens sometimes moving from a dead stop and if rpms go way down like when slowing down to make a turn. I have never had issues with icing and since I mostly do highway driving, a little throttle feathering doesn't bother me much. I only bought this carb to keep me rolling while getting my originals rebuilt, but I like its simplicity and reliability.

I would very much appreciate a more detailed explanation of the power valve mods, especially as how it could best be done when using a dual advance distributor.

Thanks!


1. To keep the power valve from functioning at all you just remove the spring that is attached to the lid of the carb with three screws and then plug the vacuum port in the lid that supplied vacuum to the diaphragm which is attached to the spring. When I first tried this, I just epoxied a broken off piece of a toothpick into the port, though there are certainly better ways to do this. You must rejet several steps richer when you do route or the engine will be way too lean, stumble badly, and make no power.

2. Supply ported vacuum to the power valve. This method leaves the power valve fully functional, but supplies it with ported vacuum instead of manifold vacuum. With ported vacuum the power valve is open at idle and thus will supply extra fuel when you are first opening the throttle where otherwise the power valve is closed at idle and thus doesn't supply extra fuel just as you open the throttle causing the notorious progressive lag. This method requires the drilling out of one plug in the lid of the carburetor and the insertion of a short nipple into the drilled hole. Ported vacuum is obtained by teeing into the vacuum advance hose to the distributor, this does not effect the operation of the distributor. It is possible to do this in a manner which is very easily reversible. Depending on your present jetting, rejetting may or may not be needed if you go this route.

Method 1 is less altitude sensitive than Method 2. So if you live in Denver and choose to go up into the mountains frequently then method 1 would be preferred.

Method 2 should allow for a bit better gas mileage, and as I mentioned above may not require rejetting.

3. A third method is the drill out the orifice in the vacuum supply to the power valve diaphragm. This will allow the power valve to open faster when you first step on the pedal. It may not totally eliminate the lag totally but will shorten it. This method is not readily reversible as once the orifice is drilled as it can not be undrill, but this isn't a big deal. This method requires no rejetting if the carb is well jetted before hand. This is certainly the easiest thing to try, though it may not work as well as other methods. Several people have reported success doing this.
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orwell84
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PostPosted: Fri Dec 01, 2017 10:56 am    Post subject: Re: Carburator Reply with quote

Thank you very much for explaining all this.
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PostPosted: Fri Dec 01, 2017 2:46 pm    Post subject: Re: Carburator Reply with quote

the good news is that the problems with a single carb can be worked out if the owner chooses to go that route. The bad news is that it is not a bolt on and go application like so many kits suggest. There is tuning and modifications involved. In many cases it is easier to leave FI on it and fix that if it is still there. And - going from carb to carb to carb may not solve the problems because they are caused by a combination of things. If you live in Hawaii. San Diego, Los Angeles basin, Phoenix etc where it is pretty warm all year, the conversion will be easier for you than someone who sees 4 seasons. However many of these places have had trouble with smog so the smog laws can make it almost impossible to run a bus with a carb. Right now everything in California pre-1976 is exempted from testing however last year there was a bill attempt in the California Legislature to overturn that and require every car made with smog gear (1968 on) to meet smog requirements of original equipment on a visual inspection prior to OBDC2. Many of you are too young but I do remember vividly when ALL cars made after about 1955 were required to add an EGR valve to their exhaust and carbs to remain licensed in California. We had a friend with a 1958 bug who had to add one to keep his car licensed - the shop went nuts trying to figure where to add a switch that normally went on a radiator as part of the mandatory EGR kit.
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machine work recommendations: http://kentcomputer.com/77VW/machinework.pdf

Pointers on rebuilding an engine:
http://kentcomputer.com/77VW/rebuilding_a_vw_engine.pdf

Setting Engine Timing: http://kentcomputer.com/77VW/Timing.pdf
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mike77777
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PostPosted: Fri Dec 01, 2017 5:10 pm    Post subject: Re: Carburator Reply with quote

Cali, Grabbing EVERY nickel they can. TPTB dislike drivers who keep vehicles for more than the car loan period, they make money on registrations, inspections, and sales tax when new vehicles are purchased. Any pre "On Star"vehicles are also more difficult to track and disable remotely. I have no idea how many of these Busses are registered in your state, it cannot be a big percentage of the total. Clean Air would have been achieved with natural market forces and zero Government meddling. The price of fuel shapes buying habits with respect to utilizing the most energy for each dollar amount spent. The manufacturers being forced to install emissions equipment, the refineries constantly re formulating gasoline blends seasonally, and the addition of 10% ethanol have caused more problems than the Government "solved" . JMO. YMMV.
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PostPosted: Sat Dec 02, 2017 3:34 pm    Post subject: Re: Carburator Reply with quote

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old license plate intake runner heater.
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PostPosted: Sat Dec 02, 2017 3:50 pm    Post subject: Re: Carburator Reply with quote

One way to reduce carburetor icing. Folded the metal down over the sharp bend near the intake ports. Wa. State required me to replace the plates after 7 years, claiming a loss in visibility on the original ones. Sounded like an absolute crock to me, I could respect them more if they simply stated they wanted more money to support the DMV operations. Perhaps the Governor's idiot cousin has a License plate stamping factory. The aluminum is easy to work with anyhow, can come in handy for patching holes also. The pervious owner had a bread pan fastened over each side, no kidding.
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PostPosted: Sat Dec 02, 2017 4:04 pm    Post subject: Re: Carburator Reply with quote

Intake manifolds Type 4 Weber IDF Dellorto DRLA Price: $80,
weber 36 idf 44/45, nice pair Price: $250 shipped,
CB Linkage and Air Filter Kit, Weber IDF and Dellorto DRLA, Type 4 Engine, 3129 $135.
Total: $465
New: Webers from ACN $800
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PostPosted: Sat Dec 02, 2017 4:33 pm    Post subject: Re: Carburator Reply with quote

Now that looks like fun! thank you Dan!! Do you use this setup? Would go all new if I go this route. Can't be any harder than synching 4 carbs on my 750 Honda Chopper.
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PostPosted: Sat Dec 02, 2017 5:16 pm    Post subject: Re: Carburator Reply with quote

No, As of the moment I don't own a Type 4 powered vehicle! They are kind of a world un-to there own! Great little air cooled engines though. Yes I know the OP just wanted a single carb. I just put this out for cost comparison. But it is definitely the way to do any carbed type 4! Otherwise just go fuel injection on them. The long manifold's required to run a single just don't work as well.
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PostPosted: Sun Jan 21, 2018 2:17 pm    Post subject: Re: Carburator Reply with quote

Wildthings wrote:
orwell84 wrote:
I am interested in learning more about the power valve mod for the Weber progressive. One mod seems to involve blocking the vacuum passage which drives the power valve. The other, which involves routing a steel vacuum line from the vacuum port to the power valve I don't really understand.

Since I will need this vacuum port for the vac can on my distributor, I think blocking the vacuum passage to the power valve would be my best option, though I am still a little fuzzy on the details.

I am experiencing the off idle stumble common to this carb. It happens sometimes moving from a dead stop and if rpms go way down like when slowing down to make a turn. I have never had issues with icing and since I mostly do highway driving, a little throttle feathering doesn't bother me much. I only bought this carb to keep me rolling while getting my originals rebuilt, but I like its simplicity and reliability.

I would very much appreciate a more detailed explanation of the power valve mods, especially as how it could best be done when using a dual advance distributor.

Thanks!


1. To keep the power valve from functioning at all you just remove the spring that is attached to the lid of the carb with three screws and then plug the vacuum port in the lid that supplied vacuum to the diaphragm which is attached to the spring. When I first tried this, I just epoxied a broken off piece of a toothpick into the port, though there are certainly better ways to do this. You must rejet several steps richer when you do route or the engine will be way too lean, stumble badly, and make no power.

2. Supply ported vacuum to the power valve. This method leaves the power valve fully functional, but supplies it with ported vacuum instead of manifold vacuum. With ported vacuum the power valve is open at idle and thus will supply extra fuel when you are first opening the throttle where otherwise the power valve is closed at idle and thus doesn't supply extra fuel just as you open the throttle causing the notorious progressive lag. This method requires the drilling out of one plug in the lid of the carburetor and the insertion of a short nipple into the drilled hole. Ported vacuum is obtained by teeing into the vacuum advance hose to the distributor, this does not effect the operation of the distributor. It is possible to do this in a manner which is very easily reversible. Depending on your present jetting, rejetting may or may not be needed if you go this route.

Method 1 is less altitude sensitive than Method 2. So if you live in Denver and choose to go up into the mountains frequently then method 1 would be preferred.

Method 2 should allow for a bit better gas mileage, and as I mentioned above may not require rejetting.

3. A third method is the drill out the orifice in the vacuum supply to the power valve diaphragm. This will allow the power valve to open faster when you first step on the pedal. It may not totally eliminate the lag totally but will shorten it. This method is not readily reversible as once the orifice is drilled as it can not be undrill, but this isn't a big deal. This method requires no rejetting if the carb is well jetted before hand. This is certainly the easiest thing to try, though it may not work as well as other methods. Several people have reported success doing this.


The #2 method is what I had been thinking of. One of the threads gave me the impression that the nipple installed into the carb actually blocked the vacuum orifice that supplied the manifold vacuum, but if I understand correctly, this is not necessary. It's not meant to block this vacuum but to also add ported vacuum to it, Do you have a photo showing where the hole is drilled in the carb? Sorry to be so dense about this but I really do appreciate the help.
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PostPosted: Sun Jan 21, 2018 2:45 pm    Post subject: Re: Carburator Reply with quote

orwell84 wrote:

The #2 method is what I had been thinking of. One of the threads gave me the impression that the nipple installed into the carb actually blocked the vacuum orifice that supplied the manifold vacuum, but if I understand correctly, this is not necessary. It's not meant to block this vacuum but to also add ported vacuum to it, Do you have a photo showing where the hole is drilled in the carb? Sorry to be so dense about this but I really do appreciate the help.


You can see it here. The nipple needs to go into the lid far enough to block the original vertical passage that supplied vacuum to the power valve diaphragm. The nipple is bent down a bit to clear my air cleaner setup.

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PostPosted: Sun Jan 21, 2018 5:57 pm    Post subject: Re: Carburator Reply with quote

Thank you. I get it now. The tube blocks the manifold vacuum source and replaces it with ported vacuum. I can see how that would affect transition off of idle.
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PostPosted: Tue Feb 13, 2018 7:36 pm    Post subject: Re: Carburator Reply with quote

Turbo 1835. any difference between 600cfm Holley versus 40WEBER sidedraft?
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