2 4bbl carb adjusting


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By Kahuna - 10 Years Ago
Gents
Hopefully, this isn't too dumb a question.
I'm trying to figure out how to adjust the idle jets (screws) on 2 4bbl carbs on an open plenum manifold?
Carbs are fine otherwise, and they run well. It's just the off-idle response is a bit rough.
Because it's an open plenum manifold, I can't seem to detect any change in vacuum signal.
Maybe it's just my approach, but thought maybe some of you experienced guys might offer a solution.

Thanks 
Jim
Kahuna
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By PF Arcand - 10 Years Ago
You might want to be more specific re the open plenum manifold, so the people on here can be more helpful.. Generally speaking, the info on this site has not been encouraging re open plenums. The symptoms you describe have been experienced by people here before.. 
By steinauge - 10 Years Ago
I dont know what carb\manifold combo you are using so this is generic 2X4 information.I have always had better luck on 2X4 setups using the rear carb idle circuit only.If you have an off idle stumble I would first back the linkage on the front carb off so that it comes in late and try driving the car on  the rear carb.If the stumble goes away you just need to adjust the linkage to bring the front carb in a bit later.If the stumble is still there I would see about increasing the accelerator pump stroke.If by chance you are using a linkage setup that opens both carbs together you need to fabricate a progressive linkage setup.There are many more possibilities but we will need to know the carb\manifold type.Good luck!
By Ted - 10 Years Ago
As Paul brings up, knowing more about your intake manifold will help.  I have dyno tested a ‘hogged out’ Edelbrock 257 intake on both the iron heads and aluminum heads and in both cases dismal low rpm performance came to the forefront.  Most of this was simply due to reversion issues that were created by removing some of the crooks and turns directly under the carburetors.  As the camshafts get larger, those reversion problems get increasingly worse.  On single plane intakes, some of those off idle hestitation issues are corrected by either tailoring the accelerator pump circuit so it adds more fuel earlier or by working with the emulsion holes in the metering block (Holley 4150/4160) and/or the air bleed holes to fatten up the fuel mixture in the mid band of the curve.  On the Teapot Holleys, first try more mixture screw adjustment and see if that helps.  After that, options become limited but the air bleed holes are located in the top cover so some fine pieces of wire put into those will give an idea of what to do there.  You can also try putting the accelerator pump adjustments in the 'winter' position on both carbs and try that.
 
Here are the links to the dual quad testing articles written for the Y-Block Magazine.
http://www.eatonbalancing.com/blog/2014/01/15/y-block-ford-dual-quad-testing-on-iron-heads-part-i/
http://www.eatonbalancing.com/blog/2014/01/17/y-block-ford-dual-quad-testing-on-aluminum-heads-part-ii/ 
By DryLakesRacer - 10 Years Ago
   I too am a little confused on an open chamber 2-4 manifold for a Y. I know Offy made them for SBC's. Here I found it best to idle on both carbs and run on the back and mine work perfectly. Mine did not like idling on just the rear one. Seem to me you should be able to cruise on the rear with any manifold as long as there are passages open to the front. Mine works fine that way and a totally open manifold should work but as Ted said not be too efficient at low speed. Others here wrote me when I was doing mine that they went back to using both carbs in unison like Ford did.      
    How big are your carb's? Mine are under 400 CFM.
    The one thing I have not done is increase the size of the fuel line feeding the fuel pump which should be done and probably is to the E code cars and the racing ones in 56. Does anyone know here? 
    One way to tell if a "Black Widow" fueley real is to look at the line from the tank...they were 3/8" from the factory not sure on the 245/270 HP's. Good luck
By Kahuna - 10 Years Ago
OK
These "Teapots" are used on a Ford Flathead engine.
The manifold is a custom piece for these carbs
They are modified ECZ 9510 1161-2 carbs. They work great.
The jetting is: M=43, P=32, S=55 (testing on a Dyno, the 43's were best)
The only issue is the off-idle roughness, probably because I'm
not proficient in the tuning aspect. But they are great otherwise.
I'll work on them again tomorrow and report back
Thanks all
Jim
By Kahuna - 10 Years Ago

http://forums.y-blocksforever.com/uploads/images/c2fcd563-efd4-4546-96f1-c047.jpg 
By DryLakesRacer - 10 Years Ago
Photo Photo Photo .....we need to see this........
By Kahuna - 10 Years Ago
I posted a pic of this thing
By YBLOCKMERC - 10 Years Ago
That is soooo cool!
By DryLakesRacer - 10 Years Ago
I am VERY impressed. What a great looking flat motor. I've seen quite a few but non like this...curiosity is getting to me...what's behind the fan? If it's a generator/alternator it is awesome.....thanks for sharing. I hope you get the throttle response figured out.....JD.
By Kahuna - 10 Years Ago
I know this is months old, but thought I'd answer the last question.
Behind the fan is a cut down generator with nothing inside except the bearings.
I got the throttle response fixed. All that was needed was to open the idle adjusting screws 
1/2 turn more. Runs great
Jim