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Unread 05-26-2011, 11:08 AM   #181
swatson454
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Quote:
Originally Posted by mtbtweety View Post
I'm now confused. I've been working on a mid-stroke lean condition, which has hopefully been narrowed down (thanks to mcmud, shawn, and a few others) to a too low float setting.
I definitely urge you to mess around with the float to see what happens but I doubt that it'll make much difference in the lean spot you're trying to tune out.

You're in emulsion tube territory now and I've been down this path before. What's most-likely happening is the signal from the discharge nozzle (auxillary ventury in Weber speak) is being bled off by the multiple, large holes that are located up high on the F-50 emulsion tubes. The signal runs down through the air correctors, goes straight through the large holes in the emulsion tubes and right on out through the boosters without picking up any fuel.

There aren't many people who understand, appreciate or know how to adjust the fuel curve when it comes to emulsion tubes but I'll lay good odds that your lean spot is much-improved with an F-6 emulsion tube on the primary side.

If you've increased the size of your primary air corrector, you may be contributing to the signal loss in the emulsion well.

This is the fun stuff


Shawn

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Unread 05-26-2011, 11:45 AM   #182
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Here's an example of what I'm talking about, courtesy of uptillnow.



The pattern of large holes at the top of the F-50 bleed off an enormous amount of signal compared to the hole pattern of the F-6. This requires more rpm to finally pull fuel in from the main circuit. Unfortunately, by this time the idle jet has already given all its got and you end up with the lean spot you're seeing.

I hope it helps.


Shawn
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Unread 05-26-2011, 12:24 PM   #183
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Quote:
Originally Posted by swatson454 View Post
Here's an example of what I'm talking about, courtesy of uptillnow.


The pattern of large holes at the top of the F-50 bleed off an enormous amount of signal compared to the hole pattern of the F-6. This requires more rpm to finally pull fuel in from the main circuit. Unfortunately, by this time the idle jet has already given all its got and you end up with the lean spot you're seeing.
I hope it helps.
Shawn
Thanks for the courtesy note...
Typically in the 38-DGES we use the F50e-tubes, using more and larger air holes. Adjust the float level to 18mm from the gasket to the top of the float (without depressing the ball and spring in the needle vale). This typically works well for “most” applications. The F6, as Shawn stated has fewer air holes, and lower on the E-tube. With less air hole’s the main circuit will tip in sooner, and be a richer air fuel ratio. So now we would need to add some of that air we took away from the original F50 until we can get what we are looking for. The float level can add or subtract overall fuel volume at the tip in, or in the middle of the main circuit, or at high RPM or MAX power.
ARE YOU STILL CONFUSED??
Emulsion tubes become “black magic” when we don’t have a wide band O2 sensor or a way to measure fuel and power changes like a dyno.
Flame suit on… Shawn, get the fire extinguishers.
UPTILLNOW
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Unread 05-26-2011, 12:39 PM   #184
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Sorry if this question has been answered or asked before, the Rear PCV valve, is there anyway to hook it up to the header or just cap it off, i was told that the PCV valves work together so the engine can breath , one sucks air in and the other lets it out , am i to assume i could just drill a hole in the bottom of the breather cover and link it up there? again this is the rear pcv valve
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Unread 05-26-2011, 12:41 PM   #185
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when i typed header , i meant WEBBER , Dang, im stupid , however that is a good idea also , run it to my header or exhaust i just installed but IDK ,
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Unread 05-26-2011, 01:18 PM   #186
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Exhaust-initiated evac systems don't work worth a damn unless you have absolutely zero backpressure. Your best bet is a new PCV in the front of the valve cover hooked up to the large port in the adaptor plates and an aftermarket breather from the "go fast" aisle at the parts store at the back of the valve cover. You can run hoses from the back of the valve cover over to the air cleaner housing for fresh air but the aftermarket breather is a much cleaner look.


Shawn
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Unread 05-26-2011, 01:26 PM   #187
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Quote:
Originally Posted by uptillnow View Post
Thanks for the courtesy note...
Typically in the 38-DGES we use the F50e-tubes, using more and larger air holes. Adjust the float level to 18mm from the gasket to the top of the float (without depressing the ball and spring in the needle vale). This typically works well for “most” applications. The F6, as Shawn stated has fewer air holes, and lower on the E-tube. With less air hole’s the main circuit will tip in sooner, and be a richer air fuel ratio. So now we would need to add some of that air we took away from the original F50 until we can get what we are looking for. The float level can add or subtract overall fuel volume at the tip in, or in the middle of the main circuit, or at high RPM or MAX power.
ARE YOU STILL CONFUSED??
Emulsion tubes become “black magic” when we don’t have a wide band O2 sensor or a way to measure fuel and power changes like a dyno.
Flame suit on… Shawn, get the fire extinguishers.
UPTILLNOW
Thanks UPTILLNOW. I've got a wide band AF meter, so I'm able to measure mid stroke mix accurately.

if I understand the (limited) reading I've done on emulsion tube theory, the float level directly ties to lean / rich at mid stroke. The F6 does look like it would produce more richness at lower float / fuel level in the bowl, or in off axis scenarios. One note, not that it matters, is that I'm not on a 38, but a 32/36. Again, I'm going to try to clean the mid lean up with raising the float level such that the fuel level is above the lower two holes, which should mean I'm getting pretty good emulsified fuel mid stroke and earlier on. If that pukes on me, I'm ordering the F6 and F7s. thanks for all the comments and help from everyone.
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Unread 05-26-2011, 01:37 PM   #188
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No matter how high you raise the fuel level with the float, you'll still be below the upper row of holes in the F-50 emulsion tube (I've physically measured it) so it won't really do much.

Definitely give it a run, though. I'm sure you have more signal in the emulsion well on the smaller, single bore of a 32/36 than I do with both barrels on a 38 so it may do the trick.

Good luck!


Shawn
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Unread 05-26-2011, 02:24 PM   #189
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To add to my last post and drawing from memory (uh oh) the fuel level at 18mm float drop covers roughly 3/4 of the second row of holes down on the F-50. Raising the float to I think 5/8ths drop brings it up to just below the upper row of holes.

Either setting will have all of the holes on an F-6 tube completely submerged. It's kind of like trying to raise the level in a glass of water by blowing through a straw but there are four big holes in the straw just above the water line.


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Unread 05-26-2011, 02:43 PM   #190
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Quote:
Originally Posted by swatson454 View Post
To add to my last post and drawing from memory (uh oh) the fuel level at 18mm float drop covers roughly 3/4 of the second row of holes down on the F-50. Raising the float to I think 5/8ths drop brings it up to just below the upper row of holes.

Either setting will have all of the holes on an F-6 tube completely submerged. It's kind of like trying to raise the level in a glass of water by blowing through a straw but there are four big holes in the straw just above the water line.

Shawn
Excellent Clarification… The fuel level on the F6 isn’t as critical as the F50, as long as there are NO holes to expose.
The fuel level does matter when using the F50. Raising the fuel level, thus covering up a hole on the F50 will enrichen the overall fuel ratio, conversely lowering the Fuel level, exposing more holes on the F50 will allow more air and leaning the overall ratio and delaying the tip in of the main circuit.
So, the F6 is good for enrichening the main circuit and earlier main circuit tip in. Also for lowering the fuel in the bowl so you can delay the fuel in the bowl from sloshing over (when you are at steep angles or axis) into the throats of the carburetor. The 38-DGES does not allow this slosh over making the 38-DGES a much better rock crawler than the 32/36 DGEV.
Shawn… Thanks for stepping up with this information. This serves allot of people who read this stuff.
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Unread 05-26-2011, 03:01 PM   #191
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Thank you sir!


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Unread 08-16-2011, 08:17 AM   #192
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Finally my weber 38 idles correctly!!!

I have a rebuild my 258 with a clifford combination package ( 264 cam, intake, duel headers) back in april along with a weber 38, 4.0 head w/larger valves and DUI. The only problem i had was that my engine would not idle with the speed screw turn in only a half turn. I tried all the available idle jets and mixture screw settings with no luck. I got so fed up with it, i just put mc2100 on.

I decided to take apart the weber to blow air through all the passages and study the carb to understand how everything worked. I could not find any problems or clogs at all. But one thing i did notice was when the with the idle speed screw was turned in a 1/2 turn, only one hole was barley exposed while the transitioning hole by the other butterfly valve was completly covered up.

So i thought maybe the two gears in the front were not synced up.
But i didnt now how to sync them up. In the weber set up instructions it does not say anything about it.

I even called redline weber and clifford performance many times and they gave the same "make sure your float is set correctly" or use differenct idle jets. Not once did they say anything about syncing the butterfly valves.

So when i was studing the carb i saw the screw on the throttle linkage and loosened it. That screw allows you so ensure that the butterflies are in sync. After loosening that screw, i made sure both transitioning holes were a barley exposed (cresent moon shape) and tightened down that screw.

Maybe my carb was dropped during shipping and that knocked the linkage out of wack.

Now after messing with this carb since april, I have finally got it to idle with the idle speed screw correct and no super rich exhaust! Hopefully i will now get better that 10 MPG.

Im posting this because i hear of people giving up on this carb. And i dont want anyone to go through the same crappy experience i went through. The carb is awesome and I can feel a difference between the weber 38 and the mc2100.

Thank you to all the guys here that have helped me and answered my questions.

Im running 55 idle jets, 170 air correctors, f-7 emulsion tubes, and my mixture screws are 1 1/8 turns out, i have zero vacuum at my ported vacuum port and my float is set at 17.5 mm from the top edge of the float to the top of the carb with the gasket on. ( i cant remember the main jet size.)



Before i put the DUI in.
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Unread 08-16-2011, 08:33 AM   #193
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I was just thinking about your progress and was going to email you. You've had a hell of a time with that Clifford! Makes me wonder why I'm considering one

I had to set my plates as well and I've kicked myself in the pants for nearly a year now for not taking pics of the procedure and posting it up on here. That's one of the reasons that I always stress pulling the carb off for a look at the throttle plates, especially if it's giving you fits.

I'm sure glad your persistance paid off!


Shawn
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Unread 08-16-2011, 10:29 AM   #194
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It's also a good reason to put a throttle stop on your gas pedal.

I've seen many Webers with twisted throttle shafts and other carbs where the throttle plates not synchronized because of twisting. DCOE were bad at this as I've seen the stop on the others side of the throttle shaft from were the bell crank was connected. Maybe the 38 doesn't have this problem but a pedal stop is good anyway.

At least your's are not a twist problem.

Glad you found the problem Now enjoy.
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Unread 08-16-2011, 10:49 AM   #195
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Quote:
Originally Posted by razor2264 View Post
I But one thing i did notice was when the with the idle speed screw was turned in a 1/2 turn, only one hole was barley exposed while the transitioning hole by the other butterfly valve was completly covered up.

So i thought maybe the two gears in the front were not synced up.
But i didnt now how to sync them up. In the weber set up instructions it does not say anything about it.
This is a GREAT find... A big problem, other than poor idle, is when you turn the engine off the throttle plate does not come down and cover that enrichening hole. This exposed hole will continue to siphon until the float bowl is empty or you restart the engine. This siphoning fuel goes into the intake manifold, down the cylinders washing the oil off the walls, and then it just delutes the oil. I believe this is true for any carburetor that has enriching holes or slots for enrichening etc.
This is the reason it is so very "CRITICAL" to keep the throttle plate below the enrichening hole (s).
Good Find, Good Fix, Good Save....
UPTILLNOW

P.S. I like the hardware used on your engine.
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