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Holley 1920 air bleed/idle transfer slot mods
https://slantsix.org/forum/viewtopic.php?t=27635		 Page 8 of 10
Author:  steponmebbbboom [ Thu Jul 10, 2008 3:07 pm ]
Post subject: 
Quote:
Quote:
Image
second shot is where the sealed air bleed adjuster screw would be, right in the center of the shot is the blank boss.
Mmmm...no, in the centre* of this shot is the blanked boss for the venturi vacuum tap used on '73-only 1920s for EGR valve signal.
OK, i was using this picture,
Image
as a reference for the boss location. where should i be looking?
point taken re: calibration hole and continental spelling. hey, does this mean i can hold you to canadian vendor links, since we're both canadian? :mrgreen:

this thread mentions links to a jpg you and doug posted for referencing internal parts and passages but i didnt see the link posted. did you want to put it up here, just to keep it all together? thanks~

ted, again thanks for your offsite help. i simply took a small paperclip and gently inserted it into the hole for curiosity's sake. of course i will have to measure everything properly before i nail this, i just saw an opportunity to contribute. when i have measurements i will post them here. thanks again~
Author:  SlantSixDan [ Thu Jul 10, 2008 3:18 pm ]
Post subject: 
Oh, OK, gotchya, I was looking at the centre of the photo and seeing the venturi vacuum tap. Now I see where you were looking. Remind me: What's your carb's type number? Is it a 7585 or something else?

Canadian vendor links: Sure, but most of the people on this site are from the YSM, so I often post YSM links.
Author:  steponmebbbboom [ Thu Jul 10, 2008 3:59 pm ]
Post subject: 
i believe so, 7585 is stamped just above the casting number but i just had the nifty box in my hands a few days ago and didnt look at the number, so i cant tell you for sure til i get back in town.
oh and ted, i am running a #65 jet at the moment.
thanks~
Author:  steponmebbbboom [ Thu Jul 10, 2008 4:22 pm ]
Post subject: 
Quote:
Dan posted the 1920 Holley rebuild guide pdf and you can easily follow the diagrams and how the idle air bleed circuit works.
this is the "jpg" i was referring to, can anyone point me to it? thanks~
Author:  MichaelS [ Fri Jul 11, 2008 8:25 am ]
Post subject: 
Ted,

My 1920 has these numbers on it: 6260 2, below that 1360. These are stamped below the bowl vent.

The air bleed hole in mine is smaller than a 5/16 drill and bigger than a 1/16 bit.
Author:  Aggressive Ted [ Fri Jul 11, 2008 9:56 am ]
Post subject: 
MichaelS,

Maybe the entrance is that big in the bowl area at the top, but is there a hole through it? Look closely at my other carb pics Dan posted, huge bowl, but no hole through it.
All my other 1920's are pinched off to were you can't even get a needle through, much less a .035 drill! As you see in the pictures my Economaster was entirely potted over with lead from the factory. So some of the 1920 carbs are tuned entirely different with and with-out idle air bleed holes.

What I have found that with an idle air bleed you get a much smoother idle and transition to the main jet with gentle acceleration, no bogs......like before. I used to mask the lean bog by mashing the throttle which would produce a healthy accelerator pump shot and mask the problem that I had under gentle acceleration, with little to no pump shot. So having the emulsion circuit working is a good thing. :D

My 1920 is shown here in several views such as the one with the green arrow pointing to the part number on the float bowl vent, #7585 1060, or R7585 is reference when you go to get a rebuild kit. Instead of kits you can purchase the gaskets, accelerator pump, power valves, floats, inlet needle and seat, etc. separately from a good carb rebuild shop. I would rebuild the carb your self. If you need the 1920 rebuild manual use the search function on this site or send me your email and I can send you a copy of SL6Dan's manual.
Author:  MichaelS [ Fri Jul 11, 2008 11:39 am ]
Post subject: 
Hole goes al the way thru. When I had it all apart I could see the opening from inside the bowl. The 1/16 drill drops right in. They must have made some with it open, why else would they have put it there for.
Author:  SlantSixDan [ Fri Jul 11, 2008 12:16 pm ]
Post subject: 
Quote:
Ted,

My 1920 has these numbers on it: 6260 2
That's your carb's type number. This carb was a Holley aftermarket replacement unit marketed for '68-'71 slant-6 engines, all applications. I just sold a new one of these to one of our members.
Author:  Aggressive Ted [ Fri Jul 11, 2008 12:21 pm ]
Post subject: 
MichaelS,

That is good thing which I have had to learn the hard way!

What #jet are you running now and how many turns out do you have the idle mixture screw?

How is your mileage?

I am running a #59 jet this week and idle mixture is out at 4 turns. No matter what jet I use 4 turns seems to be the magic spot. It will idle for ever and never miss a beat at 600 rpm.

Mileage has been 23.5 to 24.5 with a #58, or a 61-2. With the #58 I find that it dips down to and open the power valve more often when cruising. Vacuum averages from 10" to 18" and is super sensitive to throttle changes.

Running a #61-2 I find that I stay away from the power valve during cruise. Vacuum averages between 12" and 18". It seems to stay around 16" most of the time with allot of wiggle room on the gas pedal.
Author:  steponmebbbboom [ Fri Jul 11, 2008 7:36 pm ]
Post subject: 
this "artificial lean condition" people keep mentioning, does that show up on your plugs?

my base timing has always been about 7 BTDC, perhaps thats just too much for the carb's internal configuration! fatter jets might just be masking the pinging. #65 just seems too big for the center plugs to still read lean.
Author:  SlantSixDan [ Fri Jul 11, 2008 8:13 pm ]
Post subject: 
Ooh. #65s and the centre(!) plugs still read lean? Sounds severe enough to be possibly due to intake tract vacuum leaks, to me.
Author:  steponmebbbboom [ Fri Jul 11, 2008 8:35 pm ]
Post subject: 
thats what i thought too! but i just cant locate one. i worked my way up from #59 to #65 and i finally got the 3 & 4 to a liiiight brown and the 1 & 6 were dark.
the way i did it, was i removed the rocker shaft and carb, blocked off the base flange, stuck an air regulator in the #6 runner hole and put about 15PSI to the intake then used a soap solution to check the intake flanges. didnt see a single bubble. exhaust leaks just a bit at #4, but the intake is tight as a drum, nooo dooot abooot it :mrgreen:
Author:  SlantSixDan [ Fri Jul 11, 2008 8:52 pm ]
Post subject: 
Got another carb to swap on and see if it runs better?
Author:  steponmebbbboom [ Fri Jul 11, 2008 9:14 pm ]
Post subject: 
i got tons of em, but theyre all at your house! :lol:

i do need one spare while i futz around with this one. let me see how the next few weeks go. i just sunk a grip of money on balljoints~
Author:  SlantSixDan [ Sat Jul 12, 2008 9:20 am ]
Post subject: 
Quote:
i got tons of em, but theyre all at your house! :lol:
HAH! :mrgreen:
Quote:
i do need one spare while i futz around with this one. let me see how the next few weeks go. i just sunk a grip of money on balljoints~
Righto...
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