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[[email protected]]

I tend to agree.

With this much timing the idle speed screws have to be backed way off to keep the idle speed in check, there's not enough air.

Running ~8 BTDC at idle, you have to turn the idle speed screws in, and there's more air and tunability to the idle mixture. It will be a lot less touchy with less idle timing.

[rbp]

Interesting, didn't think of that. Would a few degrees of advance have this effect? I will try it at 8 and at 10 to see what happens. Hope this is it. I just find as the timing is retarded the engine runs slower, then the idle speed screws need to be turned in and then the possibility that the progression ports will be in play at idle when going for LBI.

[[email protected]]

yes the engine runs slower, and yes you turn the idle speed screws in. But your goal isn't the most "efficient", you want it to be stable, and get a good A/F. With a lot of idle advance it's often so unstable simply turning on the headlights requires a change in idle mixture screws!

If the carbs have the SVDA port on them, slip a hose on it and put a gauge on it. If you get vacuum there the idle speed screws are in too far. That's the easiest way to tell. Even a section of aquarium hose and a glass of water, if it's sucking the water up the screws are in too far (because you have vacuum there).

Just try it at 8 BTDC and see if things improve. If it does, you can keep tuning. If it doesn't, it's quick to go back.

[rbp]

Ok, so is 8 the best setting at idle? Once there just leave it and set my centrifugal to say 30 at 3000. That way the idle will always remain at 8.

[[email protected]]

for now don't worry about centrifugal and full advance, just see if the idle change makes it easier to get your idle mixture within reasonable range.

Change idle timing, reset idle speed and idle mix.

Snail gauge flow should be in the 5.5-7 range at 8-900RPM.
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[rbp]

Ok, will do. Thanks for the help.

My snails (I have 2) both read 9 - 10 range at 900 rpm. I don't think they are overly accurate but they are repeatable. 9 - 10 on mine may be 5 - 6 on others.

[[email protected]]

You aren't running 20-50 are you?

[rbp]

I am running Swepco 15-40. The snails read flow while sitting on the bench. I didn't see anyway to zero them or a calibration set screw.

[rbp]

Ok, set the timing for 8 BTDC, stacks pulled so running on idles only.

On the 50's the idle is at about mid 12, and the LM2 reads low to mid 14's when low load cruise at 2500 RPM in 2nd and 3rd gears. It has very little power and you have to feather the gas pedal to get to speed otherwise it just dies.

On the 52's the idle is still at the mid to low 12's, and the LM2 reads high 12's to mid 13's when low load cruise at 2500 RPM in 2nd and 3rd gears. Runs crisp with good power.

I did notice that turning up the idle stop screws brought the reading up but not a lot. The only way I can get the reading up to say 13 at idle would be to set the idle high, maybe 1200 RPM.

Based on this would you recommend staying on the 52's? As I explained before the crabs are new, there is no fuel that I can see dripping from the pumper nozzle, can't be the mains since they are removed, the chokes are blanked off and I don't see anything in there. I also used a flashlight and watched each barrel for at least a few minutes to see if something was dripping in but there was nothing visible.

Also this may seem like a stupid question but it seems odd to me that since the rotor moves in a clockwise rotation advance should be when the distributor is turned counter clockwise. That way the tip of the rotor hits the circuit pin in the distributor cap sooner in the engine rotation as in BTDC. Am I missing something here?

[[email protected]]

for the 50th time, the idle A/F has nothing to do with the idle jet size, and everything to do with HOW THE IDLE MIXTURE SCREW IS ADJUSTED.

If you are at 12 something at idle, re-adjust the idle mixture. Or figure out where the additional fuel is coming from. For example, pull a plug wire while idling, do all 4 cyl drop the same amount or not?
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[rbp]

Sorry, should have clarified. The idle mixture screws are dialed for LBI. At LBI the reading is low 12's. I can change that by turning the mixture screws in, but then that's not LBI. Since the guidance I have been able to get here recommends set for LBI not A/F. I am simply stating what the A/F is at LBI.

I will have to remove the carbs and find out how and where I could be getting fuel. Not sure how to verify if there are any leaks. As I stated everything is new and in excellent working order.

[[email protected]]

there has to be fuel leaks if LBI is 12 something.
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[rbp]

I have an old set of made in Italy IDF's. Perhaps I'll try those and see if there is any difference. I didn't like them due to the idle mixture screws having a blunt end rather than the needle.

[TinCanFab]

Hey, your engine looks great! Have you found your problem? From reading your posts, I think you have at least 2 issues-

Float levels: Did you take the carb tops off and adjust them? Also, cleaned the insides real well? I had new Spanish IDFs that were full of debris. It's a tedious job to adjust, and the person assembling them is NOT dialing them in for you. They are just putting them together. It's fully expected by Weber that YOU are willing to do all the tuning leg work. Bending a tab and measuring multiple times is not something an assembly line worker is being payed to do. The set I have now are old Italian, but someone put one of the floats in upside down! No wonder they were for sale because they never worked that way

Carb Setup: use the aircooled.net dual carb set up instructions and follow them to a T. I see too many discrepancies between your carb behavior and what John is saying you should see. If you are messing with the idle stop screws during jetting, you will never get it right!

In this order- clean/inspect, float adjust, bench setup both carbs too match (I use a feeler gauge), check for bent throttle shafts, verify linkage is perfect (trickiest part for me, LOTS of time here), balance carbs (doing an anal bench setup allowed me to skip work here, balance dead on at 5.5 each barrel), NOW is tuning time! You should only need to make timing and mixture screw adjustments. Messing with the idle stop screws will open the butterflies and start engaging progression ports early. Flip a carb upside down and you will see the holes in the carb body right where the edge of the butterfly is. The idle speed screw should be barely turned at all once it touches the stop. I matched both of my carbs setting here with a feeler gauge so they match, but also closed as much as possible. My engine will idle smooth from any RPM between 600-1100 RPM with ONLY changes to timing and mixture. I haven't had to touch the idle speed screws a single time since first putting my linkage on. If someone were to grab a screwdriver and turn one of them, I'd actually be super pissed!

The only way to tune these things is with baby steps and breaking the fuel and air circuits into their basic forms to tune them.
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[rbp]

Thanks for the post, makes sense and I agree with what you say.

Here is where I am at, timing is set at 8 deg BTDC and with the 50 idle jets you have to be very careful on the throttle or the engine falls down and it runs in the mid 14's which is what I was advised to stay away from.

I kept having to remove the carb tops and clean everything out with compressed air, not sure where the debris was coming from. Perhaps as you say the carbs were full of crap out of the box, they did look clean though. I cleaned and oiled the air filters just to be safe and put the .52 idle jets back in. Still had funny readings as noted above. I noticed I wasn't getting much of a response on #3 cylinder so I was playing with the mixture screw, all the way in, nothing so I thought I'd crank it out and see what happens. After about 3 turns all of a sudden I got a response and the cylinder started working. The reading at LBI was now mid 12 and low load cruise 4th at 3000 is mid 13's, low load cruise 3rd gear at 2500 is mid to high 12's.
I realise it doesn't make sense that the A/F ratio would go up when I crank open the #3 mixture screw but that's what happened and I took it out again yesterday to see if it would be the same and it is. So I figure I'm pretty good with the .52 and now have the stacks in with 230 AC's, 145 mains and F-11 emulsion tubes. I am hoping that from idle to 3000 rpm I stay with the readings I have now and I get low to mid 12's at WOT. Hope to get out on the weekend and see how it responds. Will report back with an update. I think I am very close now.

[TinCanFab]

[rbp]

Don't think so as I had the carb top off, mixture screws out and idle jets out. I then used compressed air and blew all the circuits clean, from the mixture screw to the idle jet, down through the air way at the top, into the fuel bowl and out of the progression ports. Everything was clean and air was flowing through all the circuits.
I expected that turning the screw out would let more air fuel flow into the cylinder increasing the reading on my LM-2. Not sure how its doing what its doing but I figure I'll take it.

[[email protected]]

you are speaking Greek; what does "increasing the reading" mean?

Increasing fuel, or increasing air? Richer or leaner? You need to speak our language if you want us to help.

Either refer to Lambda, or A/F.
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[rbp]

By increase I mean the numeric display on my LM-2 went up, specifically from low 12 to high 12 bouncing to 13 at idle. Increasing the reading as noted above means it is leaner, which is counter intuitive since I was opening the mixture screw (turning it counter clockwise).

[[email protected]]

You have to give us real #s, not "lean/rich", because sometimes going leaner will make the engine run hotter, other times cooler, depending on where you are when you begin.

When you turn the idle mixture screw out (backing it out) it richens the mixture at idle. If your display is leaning out, you have dirt in the carb circuit(s), or an ignition issue you have not discovered yet.
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