Looking for diagram of Weber progression circuit
 

I'm hoping this is the year I sort out the popping I have at about 2800 rpm. I want to tackle the progression circuit in the Webers and make sure that all the pathways are clear. Does anyone have a good diagram that shows the pathways in the progression circuit in 40 IDAs? I've searched all over and I've found diagrams for what seems like every other model, but I haven't been able to find a good diagram for 40 IDAs. 'Lil help?

Edoardo Weber 40 Ida 3c 40 IDS 3c 46 Ida 3c Service Manual Brand New | eBay

Do you have this manual? I have it as a PDF

Is the engine the carbs are fitted to standard?

If not the idle air corrector may be part of the issue as this can effect progression up to the level where you are having issues.

You can install a 'tuneable idle air corrector'' from Paul at Performance Oriented.

We modify this circuit as well but our 'fix' is a bit more involved to fit as we install a timesert and screw in a jet from a DGAS.

http://i197.photobucket.com/albums/a...psc66fff38.jpg

http://forums.pelicanparts.com/uploa...1426094819.jpg
Hope this helps.
I was having a problem where when I let off the throttle then lightly opened the throttle, as when you are going around a turn, there was a lot of popping and spitting.
I chased this for a year or so and finally ended up re-bushing my throttle shafts to fix it.

[QUOTE=chris_seven;8525197]Edoardo Weber 40 Ida 3c 40 IDS 3c 46 Ida 3c Service Manual Brand New | eBay

Do you have this manual? I have it as a PDF

Is the engine the carbs are fitted to standard?

If not the idle air corrector may be part of the issue as this can effect progression up to the level where you are having issues.

You can install a 'tuneable idle air corrector'' from Paul at Performance Oriented.

We modify this circuit as well but our 'fix' is a bit more involved to fit as we install a timesert and screw in a jet from a DGAS.
QUOTE]

I don't have that manual, but I would love to. I checked the ebay link you left, but the guy is not accepting orders until the end of the month and it's looks like he's out of copies anyway. I would love to get my hands on the .pdf if you know how I can do that.

The car was not originally fitted with carbs; they were added by the PO during a re-build to 2.7. I should add that this car ran like a champ in this configuration prior to this problem creeping up, that's why I think something is clogged. I've disassembled and cleaned these carbs, but I'm now wondering if I didn't pay close enough attention to the progression circuit pathways, so I'm going back in.

You should be able to follow the progression circuit from the external "veins" on the side of the carburetor.

That service manual doesn't show the progression circuit paths- I too have it in pdf. Send me your email and i'll email it to you.

Here's some excellent technical info from Paul Abbott's site.

Performance Oriented
Performance Oriented

I would strongly consider reading his entire site, as it is a GOLDMINE of information. He's on par with Richard Parr (no pun intended) of PMO in terms of Weber knowledge. They both possess an incredible amount of knowledge and are very forthcoming with their know-how. Not to mention they're both genuinely nice guys. Paul is 1QuickS here on Pelican if you'd like to point him to this discussion.

It would be good to know a bit more about your engine and current jetting including main venturi size, main jet, idle jet, emulsion tube and main air correction jet. Displacement, cams, compression ratio and exhaust type including muffler would be useful as you know it. Also, are your Webers IDTP or IDA?

The popping at 2800 sounds like a lean transition and that can be adjusted by jetting changes including the idle air jet modification that chris_seven mentions and that I also provide a kit for.

Could also be side-to-side air flow imbalance or a distributor issue, have you checked your points for proper gap? If gap is changing and the dizzy is not advancing correctly the change in timing due to points changing their gap could create a local timing issue in the advance curve...a wild guess. (Remember that I'm a carb guy more than a dizzy guy so be nice to me if the suggestion is silly.)

I have a procedure for clearing the fuel gallery supplying the idle jet which helps to resolve fuel delivery issues due to blockage. Go to my Tech 2 web page (Performance Oriented)and look for "Clearing "Hidden" Fuel Gallery".

The above procedure will clear the gallery of minor issues. If the issue is a creeping one then you might want to open the tops of your carbs, remove the floats (keep them identified to return them to their original positions) and look at the bottoms of the fuel wells to see if there is junk down there.

The engine is a 2.7 (re-built form a 2.4) with the original T cams. Side-to-side balance is good. The points are Pertronix and I timed it when I put the Pertronix in. I had the carbs apart when this problem first began and things looked clean, though I'm now wondering if I didn't pay enough attention to the progression circuit pathways. I'm not ruling out the possibility that the timing advance might be hanging up at some point, but I thought I rule out the carbs first since I'm a lot more comfortable taking apart the carbs than the dizzy.

Idle Jets are 60
Main Jets are 130
Emulsion Tubes are F-26
Air Correction are 185
Venturis are 30

Jetting sounds about right, idle jets may be a touch big but big would help avoid a lean transition. Webers are unknown (IDA vs. IDTP) but the 30mm main venturis are pretty close to the 27mm venturis the IDTP Webers were designed to use so this isn't an issue. Besides, the problem is getting worse from having worked well a while ago.

Side-to-side balance needs to be good at 3000 RPM and when throttles are opened in a manner to replicate the pull rod opening them and not by opening them by grasping the cross bar. A helper in the driver's seat who can hold the throttle open is handy for this. There are other methods for holding throttles open but the helper is the easiest.

Use the procedure I linked that discusses clearing of the "hidden gallery". This is the gallery feeding the idle jets and it taps into the emulsion tube well above where the main jet is located. These galleries are usually clear assuming the engine has been running well since debris must be sucked through the main jet before it can enter this gallery.

Check timing advance while increasing engine speed through the affected region to see if it is behaving smoothly. You can take the top of the dizzy off and manually activate the advance to see how that feels.

Hope this helps.

Thanks Paul. This is my weekend adventure. I'll report back.