Here's a strange one for ya. Have a repop carb (Holley 1920) on my /6 which tends to run fine but has a constant stumble during idle. So, I went to the salvage yard found me a nice little Holley 1920 one barrell setting on a '75-'76 Dart. Rebuilt the carb. and mounted it to my motor and this thing has soooo much suction that it won't stay running. Got the mixture screw out about 1.5 to 2 turns. The only way this thing will stay running is if I close the choke plate fully or pull off the small vac. hose running from the carb. base to the little diaphram on the side. If I pull this hose you can literally hear the air being sucked into it. The pcv valve is good. The only difference I see between this carb and the repop one is a small passageway on cut into the base just beneath the fuel/air mixture screw but not sure where it leads to. Removed this carb., put the repop back on and it run just fine as before. How can this carb. suck sooo much air? Any ideas.

Did you get the correct rebuild kit? I know a lot of the gaskets are wrong (cover holes or not) or whatnot.
Just an idea,
Frank

_________________
Scrapple: Because a mind is a terrible thing to waste.
73 Duster - Race Car
66 Dart Wagon - DD
178" FED
82 D150
All Slant powered

Believe I did. Took the Holley carb. # (6260) to the parts store with me. The looked it up in the book. The mounting gasket (between carb. and intake) was exact as my old one and the kit even provided a thick and a thin.

Jeff

The gaskets between the different stages of the carb are the ones that get you.
Ive been bit twice by this. Im by no means any good at carbs so I will bow to others that have mor expertise. Ted (Agressive Ted) is really good on the Holley 1920.
Frank

_________________
Scrapple: Because a mind is a terrible thing to waste.
73 Duster - Race Car
66 Dart Wagon - DD
178" FED
82 D150
All Slant powered

you have a vacuum leak somewhere. When you close the choke, it puts more "pull" on the venturi, causing more fuel to flow, most likely from the main circuit. Try the usual methods to find the vacuum leak.

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1979 W150 Shortbox
225, NP435, 9 1/4, Dana 44

The Good Life.

Sorry, I jacked up the whole quote thing in my last post. Meant to quote theomahamoparguy's comment "you have a vacuum leak somewhere". I'll figure out how to do this eventually.

Jeff

It may also be a possibility that you might have the EGR valve hooked up to the constant vac source instead of the EGR port. Only guessing here.
[you might not even have the egr, what year vehicle are we talking about here?]
Next thought is that the idle tube in the carb is plugged or partially plugged.
The mid 70's carbs are very lean on the idle circuit, dont take much to clog them up. Big air bleeds makes them hard to supply lots of idle fuel.
I dont know if any of this will help. I'm just thinking off the top of my head out loud sort of....
Yeah, idle circut or vac leak.....
Here's a crazy one: when I was much younger, I used to find my vacuum leaks by blowing cigarette smoke through the carb top {through straw} and watch where it came out on motor. Old mechanic told me that....
... {DONT try that}....

_________________
1979 W150 Shortbox
225, NP435, 9 1/4, Dana 44

The Good Life.

Sorry it's a '64, no EGR. Is the idle tube internal to the carb?

Jeff

Idle tube picks up fuel from below the main jet area and the passage goes up [above the fuel level] then picks up some air from the air bleed then goes back down, picks up more air bleed air [sometimes] and follows through to the idle ports and transition slot. Usually the actual idle tube is pressed into the passage that goes down to the well area {below jet}. Usually it is acessable when you remove the top casting from the carb and usually the top casting contains the air bleed. This passage in this tube is very small, maybe .030 +/-. sometimes dirt or other debris will find its way to the area just below the idle tube and it is hard to get it out.I guess they use a tube because it is easy to size for different applications and then just press it in. I imagine that a carb from the smog years would have a generous amount of air bleed size.{mixing air with the idle fuel} to try to meet the emissions of the day.
I will run a can of carb cleaner through the idle tube to make sure that it is flowing well. It is not easy though cause the hole is small and the spray tube that you get with the carb cleaner is larger than the hole that it is cleaning out. Use eye protection!!! It would be advantageous if you could slightly open up the idle tube orifice.
This is hard though because small drill bits are too short usually to reach the orifice part of the tube. This leaves trying to pull out the tube (its hard but possible) and then drill out the orifice. Also note that the passage that goes down to the idle ports follows through from the main body and into the base plate part of the carb. that means that these parts need to line up exactly and the gasket must fit making 100% sure that the hole in the gasket in no way will interfere with the flow of the idle mixture. No warpage either in these two parts where they meet.
I have not done alot of research on the 1920 as far as bleed sizes or orifice sixes go but have built a few of them along with the 1945. My 1945 had a similar problem with the idling. Turns out the gasket was coming apart and blocking the passage. Now it idles but not that great, still needs some work. Its a 1979 carb so im thinking that it could use more fuel at idle. If the vacuum is not up to par because of wear or other, this affects the operation of the idle some what. combine this with a somewhat clogged idle passage and idle problems arise. Also check for a warped base plate.
This is a long answer but I am trying to give some insight to carb workings. Its always the little things that can mess things up. Vacuum leaks-valves out of adj-ignition probs- bad carb floats etc. Trouble shooting stuff is difficult sometimes. Oh well,I guess thats why this is my favorite part of the hobby, it gives your brain a workout!!

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1979 W150 Shortbox
225, NP435, 9 1/4, Dana 44

The Good Life.

JeffDavis,

Are you sure you don't have the small bore version 1920 that came out in 1972 and 73? As you know a 75/76 didn't come with 1920's but used the 1945 instead.

_________________
Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

It's very possible that I got my years mixed up. This carb. was still mounted to the intake of the slant six when before I removed it and it's definently a 1920. How would I tell the difference? Could this cause the problems that I'm experiencing? Is this carb. still gonna be usable?

Thanks,
Jeff

Jeff,

I believe the smaller venturi bore is 1 9/16" as compared to the 1 11/16" standard bore size. Try measuring it. It was designed for better fuel economy, but limits the HP. It is still useable with reduced HP. It would probably be fine on a 170.

If you want better fuel economy and bottom end response get a R7585 Economaster. I really like mine. It is has very crisp response and power for a one barrel.

_________________
Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG