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Holley 1920 air bleed/idle transfer slot mods
https://slantsix.org/forum/viewtopic.php?t=27635		 Page 3 of 10
Author:  slantfin [ Thu Mar 06, 2008 10:39 am ]
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This is so much more interesting than the 'just get a different carb' approach.
Author:  66aCUDA [ Thu Mar 06, 2008 12:16 pm ]
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I agree I feel like Im actually learning something about the carbs. :D :D
Carbs have ALWAYS been my weak point. :oops:
Thanks for the lessons.
Frank
Author:  Aggressive Ted [ Thu Mar 06, 2008 1:03 pm ]
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Juan,
Quote:
To better identify which one works with each circuit, take a look and tell me if the small hole ends up in a well on the right side of the bowl area (let's say, the side of the "long arm" of that metering block. If this is the case, then the gunked up hole is the idle air bleed.
To answer your question, yes it does and I have some better pictures to prove it.

I sent you several more pictures this morning of my 1920 Economaster. It is a real good one of the potted large air bleed and the small air bleed. It still seems odd that the larger air bleed seems to be professionally potted.

I also took pictures if my old trusty 1963 version with two air bleeds and no deep well on the right.

I included two more shots of a 73 1920 I bought on eBay that shows the two air bleeds plus the deep well. I am thinking my Economaster should look like it. They were both built around the same time frame and have the fuel bowl vent line and have the additional charcoal canister port.

Any ideas on the design changes through the years?
why the deep well on the right and what it goes to? I thought it might be for the timed port charcoal cannister line.
And why the larger air bleed location is potted/sealed? :?:

Thanks,
Author:  argentina-slantsixer [ Thu Mar 06, 2008 1:55 pm ]
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COPIED FROM MY RESPONSE (sent you an email, but at this point there must be someone else interested in this too :wink: )

Hey Ted

As one corrects one end of the carburetion (say, high or low) to be dead on for fuel, the other end tends to suffer. If a carb is metering the right amount of fuel at WOT, it would be SUPER RICH at idle. That's where emulsion kicks in. The largest the idle air bleed (wich in all your pictures is on the left, just a tad to the right of the accel pump discharge well, that would be the "slot" that goes down the shape of the top venture at about the middle of quadrant #3 if you will, or at about 8pm.) means that the wider the rich/lean (actually about right/rich) spread is between WOT and idle.

I've seen: LARGE idle air bleed, almost non existent high speed bleed... (that would mean that the emulsion stages on that metering block is really primitive) Medium air bleed for idle, small for high speed (more elaborated emulsion stages, corrects something at WOT when PV kicks in and corrects idle) Small idle air bleed and small high speed air bleed (wich is what you'd want to see, indicates MANY emulsion stages, or a really good booster signal, and a more responsive float level in relation to throttle pressure. You'll typically see this small-small situation on Webbers, Solex, Mikunis, Holleys Economasters, aftermarket KD conversion carbs (those oval tracks fully adjustable carbs from holley or other makes) or reworked carburetors.

I'm stumped because the economaster we're referring to looks factory idle bleed plugged. Or somebody took the right tooling and did it really good.

You need to study the left air bleed insert shape on your other carbs, and then proceed to drill a rather small hole in what would have been the center of that potted hole on the economaster. DON't jet down now, as we're introducing and creating a controlled vacuum leak (that's what an emulsion stage is, a controlled air leak into the fuel stream) . Drill a small bleed like the one you have on the left and give it a go. Start with 2 1/2 turns for making it idle nice and kinda on the rich side until it's warmed up. Then we can proceed to further discuss your carb's condition wich was indeed RICH at idle and wereabouts, that's the reason why advancing the car "cured" this behavior, bit killed top end too as when PV and throttle kicked in, it was less fuel than what it would have liked. Jetting up was a misfortune because your idle and transfer circuit (wich is all the same, as well as the place from accel pump takes raw fuel) had no emulsion whatsoever. Who knows, with the proper bleed size on the left, you might be able to run fatter jetting and still get that nice mileage plus gobs of power at your throttle will, and a nice equalized cruise.

Start with a drill bit of around 1 mm (please do the math, I'm working and have no cal on me and I'm sneaking of some time from a student and don't want him to realize that I'm not paing attention to his clarinet blabbing... heheheheh) .8 or .9 is fairly close enough and safer if you have any drill bit in that ballpark

Talk to you later
Author:  argentina-slantsixer [ Tue Mar 11, 2008 6:25 am ]
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hey ted, updates?
Author:  Aggressive Ted [ Tue Mar 11, 2008 9:03 am ]
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Juan,

Fine tuning the SL6 continues to be a challenge.

After installing a the electric radiator fan (finally getting some heat in the car) I have a new found coolant leak out of another spot on the head. Apparently when I hooked the chain up to put the engine in I screwed a bolt to far in to the head and cracked a hole into the heads water jacket. No matter what type of sealant was applied to the bolt it would leak. Yesterday I installed a stud and JB welded it in, no more leak!

The water pump shaft was also pushing against the back of the electric fan about a 1/16". After getting a carbide hack saw blade I cut off about 1/4" off the nose for a nice fit. Plenty of clearance now.

Today I head to the carb shop to get 2 or 3 Economiser accelerator pump diaphragm/gaskets. When ever you open up the carb it seems they separate beyond repair. That way I can see if the idle bleed hole that I drill will line up. Next week end I will install my spare 1920 and due the surgery on the Economaster. :D
Author:  Aggressive Ted [ Tue Mar 11, 2008 12:03 pm ]
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Juan,

Just got back from the carb shop with the 8-230 pump diaphragms. My particular carb was made for 170/198/225 engines between 1968-72, R7585A, has a 1 5/16 bore and was rebuilt by Holley, still has the barcode sticker. The guys at the shop say that is common that they plug the holes, not sure why though. It sure makes for a lean low end.
They suggested that I pull the lead plug out, so it will go back to stock size. I am not sure if it will pull out that easy or not. I was thinking of starting with the #65 drill (.035) and see how it goes. I am not sure if by drilling the lead if it will all want to all come out or not.

What are your thoughts? Keep the hole small as possible or pull the plug?
The stock hole is almost 1/16" in diameter (.0625). :?:

Thanks,
Author:  argentina-slantsixer [ Tue Mar 11, 2008 3:55 pm ]
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hey

plugging the idle air bleed would get idle and transfer stages RICHER rather than leaner.

I'm not sure if they plugged that because they did wrong some modification or just for having a "fatter" low end using small jetting on a mostly city driven car. I would start with the small drill we talked about. If it's lead plugged, the drill twist action would suffice to break it loose.
Author:  Aggressive Ted [ Sun Apr 06, 2008 8:35 pm ]
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Juan,

While recuperating from eye surgery, I purchased a few more 1972 - 73 1920 Holley's. I am rebuilding one to replace the Economaster as a replacement while I am working on the Economaster. They are both the "T" bar type and have dual plunger power valves. The low idle bleeds are different on both carbs and they have the same part numbers. The entry at the top on both is a 1/8th inch well but have a brass pin pushed in from the side to block off the majority of the hole. There is about 10% of the hole left so a .035 guitar string will slide through. .035 is the same as a #65 drill. The other carbs slot/hole is even smaller. Interesting calibration......both came with a #55 jet.
Author:  argentina-slantsixer [ Sun Apr 06, 2008 8:59 pm ]
Post subject: 
Quote:
Juan,

While recuperating from eye surgery, I purchased a few more 1972 - 73 1920 Holley's. I am rebuilding one to replace the Economaster as a replacement while I am working on the Economaster. They are both the "T" bar type and have dual plunger power valves. The low idle bleeds are different on both carbs and they have the same part numbers. The entry at the top on both is a 1/8th inch well but have a brass pin pushed in from the side to block off the majority of the hole. There is about 10% of the hole left so a .035 guitar string will slide through. .035 is the same as a #65 drill. The other carbs slot/hole is even smaller. Interesting calibration......both came with a #55 jet.
I definitely need to dig out old metering blocks and photos and maybe we can put together an artichle about how you can get decent power and killer milleage with this little dependable easy to fix carburetors. Are you up to? Maybe we can sign SSD to have the "bestest" background possible about years, P/N's and such.
Author:  Aggressive Ted [ Sun Apr 06, 2008 9:39 pm ]
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Juan,
Quote:
Are you up to?
I am up for that! Our little carb shop in Everett has all of the necessary parts for the 1920 carbs :!:
Quote:
Maybe we can sign SSD to have the "bestest" background possible about years, P/N's and such.
That would be nice if SL6 Dan could do that or us. :D It sure comes up often enough. Dan is a wealth of information!
Author:  Eric W [ Sun Apr 06, 2008 10:06 pm ]
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We have got to get together some time Ted. I would really like to be able to see what your doing to your carb and do the same to a spare 1920 and metering blocks that I have. PM me and maybe we can meet at work.
Author:  SlantSixDan [ Mon Apr 07, 2008 5:23 am ]
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What-all kinds of info are we after for background/carb selection?
Author:  argentina-slantsixer [ Mon Apr 07, 2008 6:13 am ]
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Quote:
What-all kinds of info are we after for background/carb selection?
bleeds/jets sizes according to years, accel pump discharge hole size. venturi and throat sizes, etc. also P/N for chrysler specific applications... so noone would be forced to use a BBS again ;-)
Author:  Aggressive Ted [ Thu Apr 10, 2008 8:23 pm ]
Post subject: 
Quote:
lantSixDan wrote:
What-all kinds of info are we after for background/carb selection?
Quote:
bleeds/jets sizes according to years, accel pump discharge hole size. venturi and throat sizes, etc. also P/N for chrysler specific applications.
SL6Dan,

Could you help us out?
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