Packard Forum Index » Post-War (1946-54)

Hello David, in the meantime i have got a reply from Max Merrit. They have got this parts on stock:

11B-126 nozzle passage plug
11B-159 bypass bleeder screw plug
75-538 metering rod

do you think i will make a mistake if i would order their parts?
If i understand you well, you are still not sure if you will find some parts for my carb.
I thank you very much for your help and your patience.
Best regards Josef

JosefClipper47

I do NOT have the correct parts. Sorry.

dp

Hi Joseph, I set my idle to 3.1% CO. That gave me the highest Vakuum at idle, and she runs very well. At 1% you are too lean, as you know. Good luck, a good healthy carb is very important.

thank you all for your help. i have now ordered from max merrit and i am curious about the results of the overhauled carburetor, best regards Josef

Hello DP,

i hope you are well? And the passion for cars from Packard is still there?

Please allow me to return to our correspondence of fall 2020.

We have equipped the carburetor with these parts.
11B-126 nozzle passage plug
11B-159 bypass bleeder screw plug
75-538 metering rod

The idle jet has not been changed. it was standard. However, the engine is still much too lean at idle. It only runs at about 0.1% CO. The enrichment for power and rpm works. Do you have any idea which idle jet we should change to? Or could you even sell me something? I would be happy to hear from you!
Best regards Josef

Hi Josef;

For the past 14 months I’ve been hiding in the house, and only driving my Packard on solo adventures to keep everything wet and working. Some good news came in last week, in that the hospital where I previously volunteered will begin letting us back in the building providing limited and highly structured service. My first day back is next Wednesday, for some mandatory training on the new rules driven by COVID-19, and then my regular weekly shifts, unless of course another wave hits us.

From what I can tell you have the correct carburetor parts, but there seems to be a story about the bypass bleed. Early in the production of the 531S the plug was 11B-159, and then so some reason was changed to 11B-168, but the 643S carburetor (logical successor to the 531S) reverted back to the 11B-159 configuration. We are talking about starting with a #52 drill size, then changing to a #53 drill only to revert back to a #52 drill again? Since this by-pass and the basic idle mixture screw are the means to control/alter the vacuum being applied to the low speed jet I would suspect the business of the #52-#53-#52 by-pass intrigue has nothing to do with the observed lean condition at idle. I think the by-pass is there to begin the atomization process, and to a lesser extent define the nominal idle mixture screw adjustment. At this point in time there is insufficient evidence to change the idle fuel jet.

So far I’m not convinced the carburetor is the root cause of the lean condition you have observed . . . it may be, but I’m just not convinced yet. If your car has an Electromatic Clutch then you must make sure that item is not creating a vacuum leak along with the windshield wiper system. Once the known suspects have been checked we can resume with a discussion about the carburetor . . . the good news is you have the correct parts.

Now for a story about a WDO 644S with the almost the same symptom as your 531S. I was setting-up a replacement carburetor for my ’48 288, but really hoping I would never need it. When I was finished fussing with the ‘refresh’ of the back-up carburetor I put it on the engine, but I could not get the engine to idle correctly. It did however try to run better when I backed-out the mixture screws. The engine had a steady, repeating misfire, and the carburetor made a whistling sound. Once I switched back to the original carburetor all of those symptoms went away. I’m still looking for the root cause for the whistling because that’s likely a source of a vacuum leak, which depending on where it is could have also disrupted the idle circuit. The point of this story is twofold, a.) a vacuum leak can push the engine lean, and no amount of carburetor adjustment seems to help, and b.) the vacuum leak could be the carburetor itself.

Let’s loop back to item a.) above. While I’m sitting here writing this it dawned on me whenever I adjusted a carburetor I always have adjusted both screws equally, meaning if I turned one screw out 1/4 turn I would dutifully adjust the other a 1/4 turn out, and as long as the engine speed hadn’t decreased go back to the first screw for some more adjustment. The intake manifold of the Packard is dual plane meaning one barrel of the carburetor is feeding a 4 cylinder engine, while the other barrel is feeding another 4 cylinder engine, so I could have started with 4 cylinders running lean, and the other 4 cylinders running OK, but by the time I got done with it I hadn’t completely enrichened the lean cylinders, but wildly over enrichened the other 4 cylinders. You might try to investigate whether adjusting only one idle mixture screw helps the lean condition . . . and then start all over and try the other mixture screw. This is a diagnostic procedure just to determine if ‘one side’ of the carburetor is faulty . . . I have never read any Carter advice on how much the idle mixture screws could be misbalanced. I’ve always thought the answer was ‘not much’.

dp

I read this the other day and it struck me as odd, "leaning mixture increased CO" so I checked my thoughts.
CO comes from "rich" not "lean" mixtures?
CO comes from excess fuel that's not completely combusted due to lack of oxygen. About 14% excess air is required for good combustion.
So I don't know what going on here, but apparently, off the generally accepted track. So not likely to be resolved following this thinking and has transpired over a long period already.
Another brand I follow was looking for the metering rod calibration tool for these carbs, so might not be properly installed? I posted my motors manual section on this for the other guy so I include it here.

info on exhaust gas:
crypton.co.za/Tto%20know/Emissions/exhaust%20emissions.html

Attach file:

---

37carb.pdf Size: 383.71 KB; Hits: 274
38carb.pdf Size: 312.09 KB; Hits: 124

Hello David,
yes, it's about time that we can all get back to normal life. When we listen to the news here, we now have the impression that things are now fortunately getting better quickly all over the world. Especially the economy in the USA is coming back quickly. I work in field sales for industrial machinery and have only moved my company car 5,000 miles in 12 months. the brake discs always have a thick layer of rust.


Thank you for your thoughts. The subject of vacuum is very interesting. We have also wondered why the enrichment does not work or only at such a high speed that you can no longer speak of idling.
I will go back to look for leaks. The car was originally equipped with the automatic clutch. However, it was rebuilt to a classic clutch a very long time ago. I guess in the 50's or 60's. All vacuum lines that were connected to it were removed or clogged. The windshield wiper works electrically, which looks completely original. The topic with the adjustment of the mixture screws is also exciting, I will discuss this with my friend, he has turned the screws while I was busy with the measurement of the engine temperature. Would be really conceivable that we have starved 4 cylinders.
I will double check everything and get back to you. I wish you all the best for the restart on wednesday, write to you soon Josef

Hi Jim, thanks for your thoughts. These instructions for the carburetor I did not know yet, I had only one with less cut away views. This will be useful to me in any case, thank you very much, greetings Josef

Hi everyone
I just tore down my carter wdo carb and rebuilt it………well almost, I’m stuck at installing the metering rod spring. I’m sure it is simple to do but I’m not having much luck and the rebuild kit is not to detail oriented.
Here is a picture of where I am.
As you can see, where the rods go and the there is a horizontal rod like a float rod to hold then. I can’t t see how the spring goes on this, I’ve tried several way and none work.
Help.

Attach file:

---

  IMG_6185.jpeg (2,215.23 KB)