40DCOE Weber float level measurement

Mike R, the emulsion tube measuring was suggested to me - and to do it if the engine is running if its not shaking too much. I'm fighting a huge stumbling problem up to around 2200 so I'm trying to eliminate any possible problems - but also have a very rough idle.

I did try measuring with the engine off and all I could come up with to measure was thin strips of paper. I'd make a mark on it, then slide it in until the edge touched the mark, pull it out and make a mark where the 'gas line' was. I tried to do it as carefully as possible but got a pretty wide variation every time I did it - at least 3 mm.

Regarding measuring the traditional way, I was thinking wrong in that for some reason I was thinking the ball was a loose ball so had to be pushed up all of the way to close the needle valve. I now know better. I do agree with you it is a rather iffy way to do it but belive I got them all pretty close. However, it sure isn't running any better.

Most likely this weekend I'll be drilling another (very small) hole in each of the throttle plates. When I drilled holes in the plates about two years ago, it made a huge difference in idling. Hopefully another hole will help even more. There's more to it then that but then it becomes a totally different thread.

Biba

My measurement tool is a nail with the point ground off. It has three marks ground into it that correspond to the top of the carb when the end of the nail just touches the gasoline in the well. The three marks are for the upper, nominal and lower levels. I remove a main jet stack. I shine a flashlight into the well and lower the nail until it just touches the liquid. The top of the carb cover must be between the marks on the nail. The three marks are at 1.63", 1.80" and 1.97" from the tip of the nail.

Ed Prytherch
79 Spider
2 x 88 Milano Verde's

Ed Prytherch, for now I'm not understanding how it works, but since it worked for you, I'm willing to give it a go. I think I have the floats set 'pretty acurately' but this appears to be a considerably more accurate way to measure. How did you ever come by those various numbers?

(Other) Ed, I'm only running one size richer idle jets with the standard 32 venturies. All other jets are standard (Shankle). Had you been there before and after I drilled the throttle plates, I'm sure you would have agreed it made a Huge difference. That is not to say there might not have been another way to get them to idle as well as they then did (still far from perfect). Both Pat Braden suggests it in his Owner's Bible as did Jim Steck in an email regarding drilling the holes - if all else fails (and it had). Also, Tom Sahines sent me to a (4-cylinder) Triumph site which had very detailed (17 printed pages) instructions as to how to set up 40DCOE carbs. Yes, many specific to the Triumph engine, but most setting them up in general. They make no bones about drilling holes in the throttle plates if one has an earlier (I bought mine new in '80 from Shankle) pair. Jim Steck told me if it didn't help, just solder up the holes. Made sense to me. We're talking darn small holes.

I had the engine running fairly well but yesterday decided to make sure the carbs were synched properly and felt I had visually synched them very accurately by shining a light down the throats and comparing where the throttle plates were in conjunction to one another. Car then ran like crap.

Right now I'm going out (after warming up the engine) and synch them by removing one plug wire at a time to see if the engine slows down equally across the board.

I'd love to have an old fashioned set of four mercury tubes with attachments to the threads on the progression circuit hole blanking caps. I have a Sychnrometer which for me doesn't work at all.

I'd also like to have an O2 sensor gauge and just had an O2 sensor grommet installed on my Euro exhaust then blanked off. That will have to wait.

I'm no expert and sure would like to have all of the tools necessary to perform accurate adjustments - along with the knowledge of how to use them.

Biba

Biba69 said:

(Other) Ed, I'm only running one size richer idle jets with the standard 32 venturies. All other jets are standard (Shankle). Had you been there before and after I drilled the throttle plates, I'm sure you would have agreed it made a Huge difference. That is not to say there might not have been another way to get them to idle as well as they then did (still far from perfect). Both Pat Braden suggests it in his Owner's Bible as did Jim Steck in an email regarding drilling the holes - if all else fails (and it had).

Click to expand...

Biba,
No offense, but all else has not failed; you’re simply running up against the limits of your knowledge of DCOEs. For example, you say you're running "standard" jetting. The "standard" rule of thumb is that you should start a set-up with the main jets @ 4 x the venturi (which in your case could be either 125 or 130), and the air correctors at main +50 (which would be either 175 or 180) on emulsion tubes that are either F9 or F16 for a 1600 or 1750 or F2 for a 2000, with an idle jet of probably 40/F9 or 45/F9. Are these what you're running? In any case, these "standard" settings are just starting points. If you’re running rich below 3000 rpm, than you need either less fuel or more air bleed on the idle jet. An F9 idle jet has 1 x 100 air drilling, while an F8 idle jet has 1 x 120 air drilling. In other words, if you’re running 45/F9 idle jets, a change to 45/F8 will increase the air bleed by 20%. remembering of course, that the idle mixture on a DCOE is controlled by the idle air screws.

Biba69 said:

I had the engine running fairly well but yesterday decided to make sure the carbs were synched properly and felt I had visually synched them very accurately by shining a light down the throats and comparing where the throttle plates were in conjunction to one another. Car then ran like crap.

Right now I'm going out (after warming up the engine) and synch them by removing one plug wire at a time to see if the engine slows down equally across the board.).

I'd love to have an old fashioned set of four mercury tubes with attachments to the threads on the progression circuit hole blanking caps. I have a Sychnrometer which for me doesn't work at all.
... I'm no expert and sure would like to have all of the tools necessary to perform accurate adjustments - along with the knowledge of how to use them.

Click to expand...

Making sure that all the throttle plates are closed when the throttle is closed is what you do to synchronize the throttle linkage–not the carbs themselves. In other words, it’s what you do before you synchronizing the carbs–it isn’t the synchronizing itself. You synch DCOEs with the idle mixture screws. And it’s always better done with a synchrometer or a manometer, but it can be done by ear. I don’t think that pulling plug wires is going to get you where you want to go.

Again, please don’t take this the wrong way, but you ought to seriously consider taking the car to someone that can synch and tune the carbs for you. Tuning Webers is always trial and error, but doing it blind is more likely to make things worse. It’s not a tough (or an expensive) job for a specialist who does have the tools and knowledge, and you’ll have it running right in no time. Good luck.

Ed, I'm well aware I could seriously use some professional help on this. There are not many who I would trust to sort the carbs out. This is my one and only daily driver so I then need to rent a car. Not my favorite thing to do.

I assumed everyone has a copy of Alfa Ricambi's '91-'92 High Performance Parts and Acessories catalog which has a wealth of information in the back - which includes the Weber specs for various Alfa engines (I'm sure supplied by Shankle since he was a part of Alfa Ricambi back then).

As stated the venturi's are 32's, main jet 130, emulsion tube F-9, and idle jet 50F8 - the latter is one step richer. The book also clearly states to synchronize the carbs you remove the blanking screws to expose the progression holes. I shine a light down one of the venturi's on each set of the carbs then, of course, adjust using the center screw.

I'll add here that virtually everything I've read says for someone in my position (unknowledgeable) Do Not Start Changing Jets.

Tom Sahines told me there are two types of Webers, those with a 3/4 turn and those with a 1 1/2 turn. I just now set mine at two full turns after making runs. The initial stumbling is reduced at this setting. I suspect it is too rich, but I'm more interested in having it idle and to improve the stumbling. The engine continues to idle faster as I open the mixture adjusting screws. This is somewhat of a compromise spot.

If money was no object and I could find someone with a dynamometer and an unlimited supply of various jets (note: I use the term 'jet' to pertain to any of the various components which can be switched out) and is of course knowledgeable. This would also include them altering both the ignition and cam timing to their optimum - though I believe I have the ignition timing set at its optimum.

My engine (freshly rebuilt) is a 2000, with 10:1 pistons and a Ricambi street/time trial w/carbs cam which they list as a 10 performance rank and is similar to the 60's Autodelta cam. They have a 12.0 lift.

Thought I'd throw that info into the mix.

I appreciate what you are saying and am only trying to point out I feel I'm fairly knowledgeable on adjusting the carbs as they are, but know that someone with the tools, parts, and knowledge could improve on the way I have them set up.

Ed Prytherch: I fully agree with you that measuring from the top has to be more accurate. Still...one has to pop the tops and the floats themselves to adjust. Tom Sahines said he did it this way but didnt' supply the measurments. He also uses a plastic rod with the marks on it. I gather by using a light on it it makes it easy to see when it touches the gas. I like this idea, but most likely will do the nail trick in the meantime.

Thanks much to both of you. I'm open to any additional suggestions.

Biba

Biba69 said:

The book also clearly states to synchronize the carbs you remove the blanking screws to expose the progression holes. I shine a light down one of the venturi's on each set of the carbs then, of course, adjust using the center screw. ...

I'll add here that virtually everything I've read says for someone in my position (unknowledgeable) Do Not Start Changing Jets.

Click to expand...

Biba,

If I'm not mistaken, the progression holes are for 'bench' adjustment--not for synch'ing the carbs when running. In general, you want to stay away from the progression drillings.

I know you said you don't like using a synchrometer, but here's a very straightforward synchronizing procedure (from another source--not originally mine):

1. Make sure it's the carbs: Make sure the ignition timing is right and the spark plugs are clean and firing well.

2. Set a baseline idle: Start the engine and let it reach normal operating temperature. This may mean adjusting the idle speed as the engine warms up. Spitting back through the back of the carburettor normally indicates that the mixture is too weak, or the timing is hopelessly retarded. If this happens when the engine is warm and you know that the timing is OK, then the mixture will need trimming richer on that cylinder. Set the idle as near as you can to 900RPM.

3. Synchronize the throttle balance levers (that center screw): Using an airflow meter or carb synchroniser adjust the balance mechanism between the carbs to balance the airflow between them, if the rearmost carb is drawing less air than the front, turn the balance screw in a clockwise direction to correct this. If it is drawing more air, then turn the balance screw anti-clockwise. If the Idle speed varies at this point, adjust it back to 900 RPM, to decrease idle speed screw in an anti-clockwise direction, to increase, screw in a clockwise direction.

4. Adjust the idle mixture at each carb barrel: When you are sure that the carbs are drawing the same volume of air, visit each idle mixture screw, turn the screw counter clockwise (richening) in small increments (quarter of a turn), allowing a good 5 - 10 seconds for the engine to settle after each adjustment. Note whether engine speed increases or decreases, if it increases continue turning in that direction and checking for engine speed, then the moment that engine speed starts to fall, back off a quarter of a turn. If the engine speed goes well over 1000RPM, then trim it down using the idle speed screw, and re-adjust the idle mixture screw. If engine speed decreases then turn the mixture screw clockwise (weakening) in small increments, again if engine speed continues to rise, continue in that direction, then the moment it starts to fall, back off a quarter a turn. The mixture is correct when a quarter of a turn in either direction causes the engine speed to fall. If that barrel is spitting back then the mixture is too weak, so start turning in an anti-clockwise direction to richen. During this procedure, the idle speed may become unacceptably high, so re-adjust it and repeat the procedure for each carb barrel.

5. Double-check the idle: After all the mixture screws have been set, the idle should be fairly even; if the engine is pulsing, spitting or hunting then the mixture screws will need further adjustment. If the engine is rocking or shaking then the balance is out, so revisit with the airflow meter/ carb synchroniser and repeat the procedure from there.

This procedure worked well for me--it really is a very straightforward process. (I also changed the jetting, but not before making sure that the carbs were properly synch'ed.)

One further thing, although it also sounds like your jetting is indeed pretty "standard", I do notice one potential problem that could be masquerading as a float level problem. The fuel in the main wells is affected not only by the float level, but by the 'displacement' of the emulsion tubes. You're running F9 tubes, which have a diameter of 8.2mm. For a 2000 cc engine, the "standard" settings suggest you should be running F2 tubes; they have exactly the same air drillings as the F9, but they have a diameter of only 7.5mm, so there will be more fuel in the well (less fuel displaced by the tube). This will, of course, only affect the running over about 2800rpm (I know you said your stumbling was around 2200rpm), but it's probably worth changing the tubes to F2s.

Good luck.

I've arrived at a similar point. I have a smooth idle and good power under 60% -100% throttle. But if I just hit about half throttle, even with the accelerator pump working fine, and hold it, the engine begins to cough and crackle. It will hold the RPM at say, 3,000, but sounds awful. Other times it runs smooth at the same 3000 RPM. And any time I clutch it in around 2,000 RPM or less, it chokes out. And it was also spitting, and popping, but adjustment on the idle screws pretty much took care of that.

The plugs are running black, black, black.
( I am going to replace the soft mounts as they may be leaking, and I'm thinking that could significantly reduce the intake velocity. The engine often sounds like the fuel is entering the intakes in a liquid, rather than an atomized state.)

The idle screws are at about 1 1/2 turns. I haven't changed a thing for jets or floats. The jets, emulsion tubes, etc. are all exactly as specified for this 1969 GT 1300.

The carbs were disassembled, cleaned, new gasket sets, and reassembled. Timing is right on.

These are the original carbs as far as I know: 40DCOE28
#80565 and 80026.

I think I will take your advice and take the car to a professional, but I may have a time finding one around here.