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Hello gentlemen, I need advice again. What is the correct procedure for adjusting a 2 barrel carburetor using the idle speed adjusting screw and idle mixture adjusting screw? It seems that I have been searching incorrectly, but I couldn't find the exact procedure anywhere.
Let's assume that the carburetor is properly set in all other aspects (such as float adjustment, metering rod adjustment, etc.).


I would like to ask a few more things. I apologize for my silly questions, but I have never adjusted a carburetor before.

1.Which screw is the idle speed screw and which screw is the mixture screw? (1,2).
2.If the mixture screw is fully screwed in, how many turns should it be opened from this setting to achieve the correct fuel-air mixture? (Referring to the initial, baseline setting)
3.Should the throttle plates and choke plates be open or closed?
4.Should the idle speed screw and mixture screw be done on a warm or cold engine?
5.The air filter seems to be too tall for me. It's not the original one; it's a John Deere high filter measuring 55mm/2.17 inches. This is likely affecting the engine's performance as well. What is the height of the original air filter?

Thank you all.

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1 and 2 are both mixture while the unnumbered one to the right in the photo is the idle speed. I'll let the experts answer the specifics as I am only just now getting back into working on my cars after a nearly-40 year hiatus so will be watching the answers myself!

, here it shows I'm stupid/inexperienced. Thank you for your response and good luck with your work on your cars

So, am I editing the image correctly? How should I adjust these screws, as mentioned in question number 2. (above)?

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Yes, that's correct but again, I am still re-learning things I used to be able to do without even thinking about it so be sure to read the service and shop manuals which are available in the Literature Archive on this site. I believe there is a Serviceman's Training Book somewhere in there that might help too but I can't recall just now which one it was.

Incidentally, one of my former everyday cars was a 1953 Clipper Deluxe sedan and it was a great car! Much lighter than my senior models so was easier to drive.

stajgr, here's one approach to proper adjustment of the idle mixture screws. Optimum adjustment is the leanest mixture consistent with the maximum manifold vacuum. Turning the mixture screw in (clockwise) leans the idle mixture.

1. Engine fully warmed and at idle.
2. Adjust idle speed to specification.
3. Check ignition timing and correct if necessary. If timing is changed, then go back one step and reset the idle speed if necessary.
4. Install a vacuum gauge on the intake manifold.
5. Turn one mixture screw in to lean the mixture until the engine begins to falter and manifold vacuum drops. Then gradually open it (CCW) until you reach maximum vacuum and stop at that point. Then similarly adjust the other mixture screw. Then go back and readjust if necessary the first one. Then recheck idle speed, adjust if needed and then recheck the mixture adjustments.

If the air filter is suspect or dirty, service it first.

carburetion.com/CarbNumber.asp?Number=784S
(exploded view for parts locations)
I would suspect there's something in the shop manual in detail, as noted.
your other question:
The carb needle valve rule of thumb is 1-1/2 turns open. Run it in but not tight/just engaged and back it out 1.5 turns. If it's worn or the seat is bruised, that won't work and maybe parts correction is req'd. I usually take the valve stems out first time and inspect for "damage/wear" at the seat end.
commentary;
But I usual rebuild the carb first, for ethanol gas, so I've inspected and made sure it's all clean, working, and adjusted internally before using which doesn't apply here. Because, if it doesn't work, you'll be back for more questions.ie, cheap insurance.
Follow OD's method but keep track of how much you turned the screws. One way is to go both directions until it runs rough and return to the middle of those two positions. I learned "by ear" w/o a vacuum gauge. It was different world of understanding then, today it would not be unusual to stick a combustion gas analyzer on and check the mixture a bit closer and through the range of rpms to get best fuel efficiency/least emissions.
You can't tell fuel mix with vacuum, per se. There's too many things that affect vacuum and these cars are not in "new" condition generally.ie, relative measure only.
Main thing is getting the timing and idle right first.ie, sets the base line. Then go back after the mix is adjusted and recheck the idle/timing, ie returns to set point. It's a bit of an iterative process but not a fiddle forever deal. If it becomes that, something's wrong.
A craft - call a mechanic friend in and watch him/get shown the first time.
I'd probably drive it like it is and see how it's performing before messing with it, may not need adjustment? Look at the tail pipe, if it's got black soot, too rich. Maybe a little water is good.

Thank you for your help. Unfortunately, my English isn't good enough to read manuals, it would take me a long time. That's why I ask seemingly silly questions to experienced people
My '53 Packard is my first American car from this era, and I'm really thrilled with it Quote:

To "Owen_Dyneto" and "Fish'n Jim"
Thank you very much to both of you. I think with your advice, I'll manage somehow. I would prefer not to interfere with the carburetor, but it seems necessary. The previous owner installed an electric fuel pump, which worked, but the performance wasn't good. Now that I have the original pump, I need to carburetor readjust. The spark plugs were completely black, indicating a rich mixture.
I just have one more question. What is the height of the original air filter? The previous owner replaced it, but it's not the correct one, this one is taller. If I understand correctly, it will allow more air intake and affect the adjustment. I need to know the original height of the air filter so that I can fix this, as shown in the pictures above.

As I found out, the height of the original air cleaner was 1 1/4 inches.

I don't know of any Packard with an original air cleaner that was so thin. Actually, there were several types of cleaners used that had oil inside as the method of trapping dust and dirt. They had an inner steel piece with a metal mesh inside that forced the air over the surface of the oil and it was the oil that did the work.