Slant Six Forum
https://slantsix.org/forum/

Holley 1920 air bleed/idle transfer slot mods
https://slantsix.org/forum/viewtopic.php?t=27635		 Page 2 of 10
Author:  Aggressive Ted [ Mon Mar 03, 2008 7:08 pm ]
Post subject: 
Juan,

Came home today from work and had a little light left, so I pulled the #59 and tried the #55 jet. It idled nice and drove fine at cruise, but getting to cruise was quite an experience. It had a very, very long bog before it got going even with the power valve on. Tried a a 56 and it was a little shorter bog. Tried a 57, shorter yet, so I put in a 58 for tomorrows drive just before we ran out of light. It is pretty cold out, 38 degrees. Being it is so cold the jet changes were pretty significant. Each increase made it more driveable and the transition on and off the power valve, much smoother.

On close examination tonight the idle bleed hole is smaller than a pin that comes in a new dress shirt, which measesured .023 in diameter. I flushed everything out with spray again, no change.

Any thoughts on what drill size to try first on the idle bleed? I would like to get back to running a smaller jet again. Gas prices just hit $3.69 out here.

Thanks,
Author:  argentina-slantsixer [ Mon Mar 03, 2008 10:12 pm ]
Post subject: 
well certainly I can notice a disbalance in the idle/transition vs cruise and power circuits. I blame that on the excellent signal that economaster boosters has. I can tell you, the idle air bleed is smaller than what I'd run on the other air bleed :shock: so let's do this: we'll work on them idle and fast air bleeds and if this doesn't work I'll turn up new inserts or better yet threaded inserts for you and send them up there in a letter.

We're going to do this: disassemble all the carburetor from the engine. Using a tool like this http://tinyurl.com/2xn7w7 (because is slender and long and it's 4 bucks) turn your carb upside down and using a plain drill bit, turn it by hand, trying to remove the material you're cutting every 2 or 3 turns so hopefully debris wouldn't clog the circuit. I'd start with a #65 drill bit. Get them in HSS because brass can break carbon steels. I'd use a #61 myself... but starting out with a #65 gives us room for improvement or panic stop and going back (you just lay a small steel ball over the enlargened hole and using a pin extractor of about 1.5 times the diameter of the ball, hammer the hole slightly and it would be reduced in diameter) If the #65 drill bit shows us improvement, I'd go to the #63 and then the #61 if those drillbits arre inexpensive. I know that I can get them dairly cheap, don't know about you. If you master the "working in a pinch" technique you would be able to do this without having to dismantle your carb appart every time and waste a gaskets kit. One tip: don't blow compressed air from the same end you just drilled, with the carb still upside down, blow a generous stream of comperssed air thru the idle discharge hole and the idle transfer slot.
Author:  65Dodge100 [ Mon Mar 03, 2008 11:26 pm ]
Post subject: 
Ted, Juan,

Here’s a pin vice that comes with some bits.

http://tinyurl.com/2u2kd4

And here’s a drill set from #61 to #80 if you want to splurge.

http://tinyurl.com/3akdg9

They may be cheaper somwhere. I didn't look too hard.

Danny
Author:  argentina-slantsixer [ Tue Mar 04, 2008 2:36 am ]
Post subject: 
Quote:
Ted, Juan,

Here’s a pin vice that comes with some bits.

http://tinyurl.com/2u2kd4

And here’s a drill set from #61 to #80 if you want to splurge.

http://tinyurl.com/3akdg9

They may be cheaper somwhere. I didn't look too hard.

Danny
thanks Danny

I just recommended that unit because it's about 1/4 in diameter, and just a tad shy of 6" long. It's perfect for drilling in tight spots without marring other surfaces. I use it to pry pads on saxophones and clarinets and sometimes 3/32" thicker would not fit in some places. That's a sweet deal though, if those drillbits are high speed steel. Carbon steel would not be good because brass "grabs" more than steel, especially when enlargening bores, and that can cause carbon steel bits to break.
Author:  Aggressive Ted [ Tue Mar 04, 2008 9:11 am ]
Post subject: 
Juan,

I will try to get some drill bits today. Just to be clear, I am only drilling one air bleed hole when looking down the throat from the top of the carb, correct?

I have an early 70's Holley carb book and it has several cut aways of the 1920 Holley carb. It shows only one air bleed hole that feeds both high and low speed circuits.

If I can find the some good drills today, I will take the carb off and drill the holes tonight. Hopefully when this air bleed is opened up, I will be able to use a smaller main jet again.

It's kind of odd how this problem gets worse as I lower the initial timing. It is more obvious at 12 degrees than it was at 14, 16 or 20 degrees. Is that because of the higher velocity of air going through the carb at the higher timing settings?

Thanks for the info! :D
Author:  argentina-slantsixer [ Tue Mar 04, 2008 9:31 am ]
Post subject: 
no, that would be on account that higher ignition advance creates (or simulates) an artificially lean condition. If you want to shoot me an email with the cutouts to jicaino at gmail dot com I might be able to come up with more ideas.
Author:  emsvitil [ Tue Mar 04, 2008 2:32 pm ]
Post subject: 
If the air bleeds are brass, you can always fill with solder and redrill.........
Author:  argentina-slantsixer [ Tue Mar 04, 2008 4:02 pm ]
Post subject: 
Quote:
If the air bleeds are brass, you can always fill with solder and redrill.........
can you believe that I never thought of that? I always turn another one in the lathe, pop the old one and replace it... :roll:

is amazing how you (I) can manage to make life more complex with this tiny things! :shock:
Author:  Aggressive Ted [ Wed Mar 05, 2008 8:03 am ]
Post subject:  1920 Holley Economaster Tuning
Juan,

Got the drills last night on the way home, #65, #63 and a #60, (.035 - .040).
On the comment on the brass, my Economaster is all aluminum, no brass. If I mess the tuning up I could drill over size and insert a brass tube, then I could use solider for corrections as emsvitil suggested.

Brought my old Holley book in today to scan, but I see Dan already posted the 1920 Holley Manual. Thanks Dan!
On page two they show the idle air bleed and high speed air bleed, they are the same hole?????

Tomorrow I will pull the carb and try drilling with the #65 drill bit.
Author:  Wizard [ Wed Mar 05, 2008 8:37 am ]
Post subject: 
Aluminum?

Certain this is not potmetal?

How do I know I went too far with leaning out, which I have quite way to go.
Um what about the secondary jettings? By the way, I got the air/fuel gauge for the narrow band O2 sensor, I know the limitations with these just as a general status.

Cheers, Wizard
Author:  argentina-slantsixer [ Wed Mar 05, 2008 1:38 pm ]
Post subject: 
I have yet to see a SINGLE air bleed holley in any flavor. In the cutouts works like a charm because those would be either shifted left or right from the center. High speed and idle air bleeds should be very different in diameter for any stock carburetor of that era. Can you snap a quick picture from top venturi?
Author:  Aggressive Ted [ Wed Mar 05, 2008 2:32 pm ]
Post subject: 
Juan,

Sure! The one air bleed location on the passenger side is plugged with a small piece of wire or string with epoxy over it. The one on the right or drivers side (looking from the front of the car) is the only one that is open. This is the only 1920 Holley Economaster carb that I have however, I have three other standard "T-bar" 1920's a 1963, 67 and a 73 version. I will see if they have two air bleeds or just the one air bleed.

Since low and high circuits are running off the one air bleed, I am lean off and on at various rpms. It is interesting to look at the vacuum gage and see how it responds. The surge from letting off on the gas at cruise to getting back on it is interesting. It is like a big hiccup. The bigger main jets disguise it some, but it is still there. Especially when going down hills. So I do have a high speed air bleed problem too, not just the off idle bog. Once you go below 10" of vacuum, you will never feel anything because the power valve is engaging or when the choke is partially on in the morning.
Those conditions make it feel like a nice smooth running engine.

Despite these conditions last night when I filled up I still got 22.5 mpg. I know it isn't great but, I pushed the car pretty hard though the last two days, plus lots of stop and go traffic. :D
Author:  argentina-slantsixer [ Wed Mar 05, 2008 2:52 pm ]
Post subject: 
now we're making sense. If ytou have your idle air bleed shut off (that's what that nasty wire epoxied is doing) you can run super smaller jets, but your high speed idle is going to bite you in the ass.

I don't think your carb has all aluminum construction (or white alloy, generically speaking) bleeds. All holley bleeds are pressed on brass inserts. They they do the dicrhromate treatment so it kinda "hides" the color difference. You also should have brass plugs at the base and depending on the year, soft aluminum, lead or brass plugs over other circuits.

Now, DON't ream the high speed bleed, because you're going to make the power condition worse (and your mileage may not suffer but you're going to be powerless out of lean condition) I'd rather remove the epoxied wire. Since you're trying to introduce some air into the idle circuit, I might start with hypodermic needles sections epoxied over what should be a rather BIG hole (1/16" ballpark for your typicall 1920) I don't know if you can have access to needles and such without raising eyebrows, I find them really easy, because my wife, father and mother are doctors, so, I often find myself using resoruces that migh be a pain in the ass to get elsewhere. Needles comes in gauges, a 21G needle should be a good start if you can get it. K&N engineering co from chicago sells prime quality brass tubing for modelers of you can't get needles, and they have an impressive stock of shapes and sizes. The smallest hollow brass tube may suit you just fine.

now, let's recap for a minute: I'd use a 1/4" piece of a 21G needle REPLACING the wire that's shutting off the hole in the passg side, and seal it again with epoxy. And DON't jet down, as you'll be actually activating the idle air bleed. Make sure you insert a piece of wire inside the needle and cut it off with say a dremel cutoff wheel or a wire cutter then using a grinder try to get nice, smooth edges, and then remove the "stuffing" inside that little tube with a pin. Using a proper drillbit, ream (as in countersink) both ends of your "insert".
Author:  Aggressive Ted [ Wed Mar 05, 2008 7:52 pm ]
Post subject: 
Juan,

I just sent you four pictures. It was dark out so it was kind of hard to lean over the carb and shoot in the dark, but I think they maybe good enough for you to advise me. You will see the high speed hole is entirely potted, the low speed has about a .020 hole, the squirter hole and a huge hole that goes somewhere......not quite sure if it goes to the charcoal filter fitting or not.

Thanks,
Author:  argentina-slantsixer [ Thu Mar 06, 2008 2:13 am ]
Post subject: 
Quote:
Juan,

I just sent you four pictures. It was dark out so it was kind of hard to lean over the carb and shoot in the dark, but I think they maybe good enough for you to advise me. You will see the high speed hole is entirely potted, the low speed has about a .020 hole, the squirter hole and a huge hole that goes somewhere......not quite sure if it goes to the charcoal filter fitting or not.

Thanks,
red your mail. The large hole is the idle air bleed. The small hole is the high speed bleed. As funny as it's sounding... :wink: To better identify wich 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. No wonder why 1 or 4 turns where all the same, you weren't having emmulsion at all in idle/transfer circuits. Will ellaborate a longer response during the day, with pictures and all. Just let me put back my 2 notebooks together, (dissasembled both for fixing them... bad idea!)
Page 2 of 10 All times are UTC-08:00
Powered by phpBB® Forum Software © phpBB Limited
https://www.phpbb.com/