We need to know the number on the main and aux ventruris as well
Three Webers
- Thread starter Rod Cole
- Start date
Get an authentic German made synchrometer (most sold are Chinese knockoffs). It will make synching the carbs easy.
In checking for tightness of the manifold I see these "spring washers" on the carbs - Anybody know the right way to tighten these, how tight is tight?Far from an expert, any old timers here might say now there’s a guy who is to afraid to be wrong...
but sometimes it takes a couple of stupid ideas to expose the right ones, to short circuit a couple of synapses...so...
...if the car accelerates fine but has surging at steady rpm, maybe th issue s a vacuum leak.? Have all the mounting bolts and all the screws around the top edge of the carb been checked. They like to loosen...Doesn’t the Weber manual say that most carb problems aren’t carb problems. .. I love that phrase... Linkage is so often the issue.
Last week I was trying to cure a hunting issue with an air cooled v dub and after taking the carbs linkage and ignition apart...it turned out to be a missing gasket at the base of the mechanical fuel pump.
Al
I hand tighten the spring washers until snug. To check these, buy some starting fluid and spray it around the washers. If you get an increase in rpms, you have a leak and the nuts are not tight enough. If you don't get a surge, don't mess with these.
I had a surge problem that turned out to be a worn out one way valve in the vacuum line leading to the brake booster. Cheap fix. To test this, pull the valve from the car and blow into it. I believe yours is located in the middle of the picture you posted right over the center carb. It should flow in one direction and not in the other. If it flows in both directions it is defective and needs to be replaced. And while you are doing this, look at the integrity of the vacuum hoses. Make sure they are not cracked at the attachment points.
I had a surge problem that turned out to be a worn out one way valve in the vacuum line leading to the brake booster. Cheap fix. To test this, pull the valve from the car and blow into it. I believe yours is located in the middle of the picture you posted right over the center carb. It should flow in one direction and not in the other. If it flows in both directions it is defective and needs to be replaced. And while you are doing this, look at the integrity of the vacuum hoses. Make sure they are not cracked at the attachment points.
Looks like you still have a ‘73 cylinder head on the engine. How is it running temperature wise?
I can't really comment on heat due to just doing short road tests on the work being done, but never saw it much more than half to three quarters thru the scale.
Today I did a valve adjustment, #1 intake was a little tight, all the rest fine. Also checked the timing & plugs & set the fuel pressure to 2.5
Does anybody know anything about that Crane Cams ignition, something I didn't know existed. But the strangest was finding no "dog" to lock the Dist. cap from turning. There is a notch in the housing, but nothing to match on the cap.
The good news is the surge isn't as bad with the pressure turned up, almost gone. Once I get a synchrometer & AFM in hand, I'll see what's up in the carbs~
Today I did a valve adjustment, #1 intake was a little tight, all the rest fine. Also checked the timing & plugs & set the fuel pressure to 2.5
Does anybody know anything about that Crane Cams ignition, something I didn't know existed. But the strangest was finding no "dog" to lock the Dist. cap from turning. There is a notch in the housing, but nothing to match on the cap.
The good news is the surge isn't as bad with the pressure turned up, almost gone. Once I get a synchrometer & AFM in hand, I'll see what's up in the carbs~
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Hi Rod -- another thing I would do if I were you is to remove the cold start mechanisms. In looking at your pictures, these are not hooked up to a cable, which means you are not using them. They can be a source of a handful of different problems. Buy block off plates with the proper gaskets and install these in place of the cold start mechanisms. This can easily be done with the carbs on the engine and eliminates a potential source of trouble.
Eliminate the thackery spring washer/o-ring system and replace with JIS nuts and regular base gaskets from Pierce Manifold. Not needed on 6 cylinder engines and will haunt you forever!
Another thought from looking at your picture. You have stains on the tops of all three carbs, which might be coming from improperly sealed "Mickey Mouse Hats." This can cause vacuum leaks and hence your hesitation. Pull each of these and check to ensure that the gasket between the hat and the top of the carb is in place. Then make sure these are properly centered and snug.
jmackro
Well-Known Member
Just to provide the dissenting opinion:
- While the enrichening devices (AKA "cold start mechanisms") might potentially be a source of problems, they aren't inherently unreliable. I will agree that if you will never use them, then you might as well remove them. But...
- Why wouldn't you use them? I have dual DCOE's on my Alfas, and always use the enrichening devices to start the engine, as well as to allow it to idle when cold. I don't live in a cold climate and can't imagine not using them if I did. My sense is that if you don't use the enrichening devices you have to jet the carbs on the rich side to allow the engine to start and idle when cold.
Question for extra credit:
Alfas have their carbs on the right side of the engine, so the cable set-up for the enrichening devices is simple: pull the levers rearward to enrich. BMW's have their carbs on the left side of the engine, so the cable set-up is more complicated: the levers need to go forward to enrichen, so the cable needs to make a "U turn" ahead of the front carb. Are enrichening devices available with opposite parity; that is, with the lever on the other gear, so that pulling the levers rearward on a BMW will enrich?
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The mickey mouse covers wont create a vacuum leak but will allow fuel to seep out. The jet area under the covers is vented from the hole on the face of the carb by the left venturi and will be unaffected with the covers off.
I don't use the cold start circuit and have them plugged. I dont mind waiting a couple minutes with foot on the pedal to warm the engine until it idles by itself. It's my preflight zen moment. If you jet richer just to have better cold start then your idle and low load afr will be very rich when warm/normal operating temp.
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Have to say, that phrase just made me smile.
Has stains: the fiber gasket under the jet cover often weep a bit of gas, staining the carb top cover. You can get neoprene replacements that greatly reduce this. But your carbs will be covered by the air box so it really doesn’t matter
Lots of good tips in this thread!!!
I have been advised that I should use them, but have not done so. Until I get other things sorted, this is lower down my priority list. I have acquired a cable and scouted routing and a location under the dash for the pull. I was actually thinking about a push to enrich/pull to drive setup.
jmackro
Well-Known Member
I have manual choke Weber 32/36 DGV's on my coupe. I put the choke knob in the dash below and to the left of the steering column, down where the emergency flasher and rear window defroster buttons are.
You might get away with that. The challenge will be finding a wire stiff enough to compress the springs in the three enrichening devices without kinking, and with enough friction to hold its position in the "IN" position.
I must agree, and have to say I'm very impressed with how much help I got so quickly. This is an excellent community !!!!
Agreed Rob! One could have easily expected to see a "this has been covered, use the search" response. There are some great reference threads on DCOE's. I've read them all but some of the tips on here weren't covered IIRC.
Some of us, uh, more mature, members of the forum are not particularly keen on "use the search" since we are not good at this ourselves. In addition, because of the variations in our engines -- not only because of modifications, but also because of variations engineered by BMW, particular installations and engines wearing at different rates -- much of the prior coverage is difficult to port over to another car. Personally, I find help linking the symptoms I am observing to particular elements of a carb setup (linkage, idle circuit, fuel delivery, etc.) to be the most valuable. I can dissect and address the problem much faster this way.