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Posted by: AE354803 Aug 14 2013, 09:09 AM

I have 40 IDFs on a new 2056 (webcam 494 cam, 050 distributor, compufire points). Carbs were just rebuilt and are clean, new fuel pump, lines and fuel filter.
My current jetting is
130 main
F11 emulsion
190 A/C
50 idle jet
32 mm vents (31.5 mm actual ID) there was no marking on them.
45 2ndary vents

I preset the carbs as described in tom wilson's book. Timing is set to 30* BTDC at full advance. Once I had everything synched my idle was about 1000 rpm and very steady. I tried to dial it down to <900 rpm as stated in the book. In order to do this my idle screws are backed out entirely and the only way to lower the idle speed is to attach extra return springs to help pull the throttle plates closed.

I'm not sure whether I should pursue getting the idle speed low or just leave it at 1000 rpm. It idles really well there.

Air Bypasses are all less than 1.5 turns out. Idle mixtures started at 3 turns out and were adjusted per the book from there.

Not sure where to go with this one or if I should just leave the high idle.

Thanks, Andy.

Posted by: stugray Aug 14 2013, 11:57 AM

Did you disconnect the "master" throttle cable and any linkage you have between the carbs?

This is how you are supposed to do the initial setup and might help you find your problem.

Sounds like either your butterfly valves are not in straight (keeps the butterflies from closing all the way) or your linkage is binding up somewhere.

Oh, and your air bypass screws should be all the way closed.

Stu

Posted by: AE354803 Aug 14 2013, 01:42 PM

I inspected the butterflies during rebuild, they closed appropriately, one may have been a touch higher than it should be but nothing major. All linkage was disconnected during the initial sync and idle as instructed.

I'll give the air bypass screws a go tonight and see if that helps.

The only other thing I could think is a manifold leak but they are all pulling the same according to the snail flowmeter so I don't think it is that.

Posted by: stugray Aug 14 2013, 02:27 PM

What is the number?
Mine pulled 5-7 on all 4 barrels when the engine was barely running.
My instructions say for initial setup that it should be "running like a tractor"
The RPMs were not even registering on the Tach, but the engine kept running.
That is with 3/4 turns in on the idle adjust AFTER barely touching the arms.

I was able to set the idle mixture screws during that phase.

THEN I turned up the idle adjust screws, set idle balance, and reattached the linkage.

Stu

Posted by: URY914 Aug 14 2013, 02:32 PM

Check to see if the carb/manifold and manifold/head gaskets are leaking by shooting some carb cleaner at them while you have it running. If the speed of the engine changes your leaking somewhere.

Posted by: AE354803 Aug 14 2013, 02:46 PM

They were all pulling at 5, after I adjusted the air bypass. Before that adjustment I would say 4.75-5.5, somewhere in there.

I'll check for leaks with carb cleaner tonight. I'll check torques just to be sure also.

Posted by: stugray Aug 14 2013, 03:01 PM

I followed this:

http://www.redlineweber.com/html/Tech/idf_adjustment_controls.htm

"They also have an additional air bleed screws and lock nuts. This is not used for idle adjustment or idle quality. The settings for these screws should be closed. "

So why were you adjusting the air bypass screws?
I have no idea what they are for, so just curious.
I cannot imagine that our snail sync meters are accurate enough to see such small adjustments required by the screws....

Stu

Posted by: AE354803 Aug 14 2013, 03:29 PM

I could see small changes, for instance going from 4.75 to 5, they were slow and hard to see but there would be a gradual change and then re-stabilization. IIRC the tom wilson book said to use the air/bypass screws to get the final adjustment, but to start with them 1/2 turn out. I didn't touch the air/bypass screws until the way end to dial in the last little bit of flow mismatch. From my understanding of the carb flow diagrams the air/bypass is just a controlled manner of allowing air to pass by the butterfly and idle circuit without introducing more fuel (a controlled air leak if you will).

I guess there are different ways to skin this cat.

Posted by: r_towle Aug 14 2013, 05:54 PM

Pull one plug wire at a time to see if you find a dramatic change.
Start with the butterfly that you said might be off.

Rich