I got them from @Mike Goble and he usually finds all his stuff on BMW's at self service wrecking yards. I'll ask him if he remembers where mine came from. Pretty sure they were on an M30.
Weber 32/36's - can't figure it out!
- Thread starter dang
- Start date
I would assume they're from his car. I think he's using 38's now. I'd also wager the jetting is:
Primary- idle 60; main 140; air corrector 145
Secondary- idle 55; main 170; air corrector 175
Based on these assumptions I'd check the choke plates are open (per Ohmess) since it sounds like you made a change there and then check your mixture screws-- while it's running (chokes open) start turning them in and see if it raises the idle. Sorry if I'm stating the obvious but I can't tell if you've tried this yet.
Drove without air filters and it seems about the same. Choke plates are opening all the way up. Front carb idle mixture is at 1 1/2 turns and the rear carb is at 2 turns before they start to make idle go lower while turning them in
Only if you are following a car that's running rich.
I was serious about the painted carbs bit though. New paint is really fumey when you first use it on a hot engine .
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Did you turn the mixture screws out until the idle stopped increasing? About how many turns was that?
Do you have the cut off solenoids? If so, when you unplug them does the car die?
Last one- plugs are sooty?
If all that is fine I’d move on to ignition and make sure baseline settings.
Was there a problem with the zeniths?
Do you have the cut off solenoids? If so, when you unplug them does the car die?
Last one- plugs are sooty?
If all that is fine I’d move on to ignition and make sure baseline settings.
Was there a problem with the zeniths?
Okay, a little more info. I got the top off of one carb last night and here's the numbers.
Primary
Idle: 60
Main: 140
Air corrector: 160
Emulsion tube: F50
Secondary
Idle: 60
Main: 140
Air corrector: 170
Emulsion tube: F50
Primary
Idle: 60
Main: 140
Air corrector: 160
Emulsion tube: F50
Secondary
Idle: 60
Main: 140
Air corrector: 170
Emulsion tube: F50
I took the power valves off to inspect. I have four total with two parts carbs and they all look the same. The diaphragms work as far as move up and down freely without any obvious damage but I really don't know how to tell if they're good. I tried using a vacuum on the orifice connected to it and couldn't get it to move, on all four. Not sure what to do now.
I'm using a Facet electric pump right now and it's only suppose to provide 3-4psi I think. I need to get numbers for setting the floats. They need to be checked.
So, I understand the "power valve" is used to enrich mixture at full throttle. I would think this is unlikely to be your problem because it looks to me like the spring would act to keep the valve closed most of the time. Are you finding information on the net that indicates that they might leak?
Otherwise, I would think you should initially concentrate elsewhere. I like Shanon's suggestion to check your float levels, and while you are at it make sure the floats are empty. Sometimes they develop pinholes and fill up with fuel (this is more likely with brass floats). If they don't float they won't stop the flow of fuel into the bowls, and having too much fuel in the bowls messes up everything.
Otherwise, I would think you should initially concentrate elsewhere. I like Shanon's suggestion to check your float levels, and while you are at it make sure the floats are empty. Sometimes they develop pinholes and fill up with fuel (this is more likely with brass floats). If they don't float they won't stop the flow of fuel into the bowls, and having too much fuel in the bowls messes up everything.
So far all I know is the floats don't leak. I need to get baseline numbers to check/set the float level.
As far as the power valve goes, they're new to me so I'm just now trying to understand them. The way I understand it is, the shaft of the power valve sits on top of the valve at the bottom of the bowl. When the shaft is down (fully extended) the valve is open. This means the valve is open while the engine is off. When the engine is running and has normal vacuum the shaft is lifted off of the valve so the valve is shut (no extra fuel), but as soon as the vacuum drops, like during WOT, the shaft drops back down and depresses the valve and allows fuel to be drawn through the venturi with the main jets. If this is the case, if the diaphragm is bad, the shaft doesn't get pulled off of the valve at the bottom of the bowl so the extra fuel is always present.
EDIT: I have a couple extra power valves and I think they're bad anyway. Seems like I could shorten two of them and see if it makes a difference, since this would presumably close the valve for extra fuel.
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'69 2800cs
Well-Known Member
I think it was sreams who mentioned bad power valves causing a rich mixture years ago.
I replaced mine prior to my tuning journey and it stopped the “stinking rich” at idle symptoms I was experiencing.
I replaced mine prior to my tuning journey and it stopped the “stinking rich” at idle symptoms I was experiencing.
I just used that diagram to adjust one tonight. I'll do the second tomorrow. The first one was high quite a bit
Exactly. A leaky power valve diaphragm will cause the power valve to be ‘on’ all the time. That’s why you are right to check it if you have an over rich idle or progression phase.
FWIW, I would adjust the idle mixture screws about half way between the too rich and too lean point as a starting point, and not that the richest good-idle setting as mentioned above. But what you really want to do is optimize your AFR not at idle but as you drive. Adjusting the idle mixture only helps if the rest of the setup is already dialed in (eg good jetting selections).
For this reason I use an aftermarket wide band O2 sensor tool that provides real time AFR and adjust idle for leanest good driving characteristics. By the way, if you are way rich in easy going driving around town, the main circuit can still be a contributing cause. It was in my case (DGAS38/38).
Dang - thanks for the power valve explanation. It appears I was mistaken about the way the power valve functioned. I now understand it is "on" unless it experiences a certain amount of vacuum.
Nonetheless, I believe its ability to function properly depends not only on having a functioning diaphram, but also on the fuel level in the bowl, and thus on float settings.
I've looked at this only briefly, but I think a high level of fuel in the bowls can diminish the effect of engine vacuum on the valve.
If I am right (and even if I wrong about this, proper float settings can't hurt), making sure your float levels are correct should be the next step.
Nonetheless, I believe its ability to function properly depends not only on having a functioning diaphram, but also on the fuel level in the bowl, and thus on float settings.
I've looked at this only briefly, but I think a high level of fuel in the bowls can diminish the effect of engine vacuum on the valve.
If I am right (and even if I wrong about this, proper float settings can't hurt), making sure your float levels are correct should be the next step.
I checked them last night and one was set too high. I've also rigged both power valves to be shorter so they'll be taken out of the equation as far as richness goes. I'll be firing it up tonight and hoping for progress.
Here's three of the power valves I have. The one of the left has about half of the rubber membrane left and the other two just have the fabric material exposed. There's no way any of these can work properly. I'm ordering two new valves but in the meantime I'll test without them working.
This is so familiar. I look at those power valves, and from here, they all look expired. But I would do the very same thing you are doing. Swap, experiment, evaluate, obsess, and finally spend the money. But we are all very entertained at the sequence of events here. Carry on, Dan! 
My Weber power valves arrived. I bought them from an Italian company through U.S. eBay. Brand is "Weber" although they're not marked anywhere, but they're really good quality and I don't question their OEM-ness. I'm sure I could've found them in the states somewhere but it was easy and didn't take long to get here.
Their website... https://carburatori-italia.it/en/
Their website... https://carburatori-italia.it/en/