So I posted on this topic a few weeks ago, but then I got sidetracked by several other projects on this car, subsequently finding out I had the wrong spark plugs in my engine. I hoped putting the right plugs in would have more of an impact on my engine's performance, but it didn't make much of a difference.

So before I drop a jet size on my Weber 32/36 tomorrow, I thought I'd find out, using the plugs I just pulled as an additional diagnosis, if there's anything else I should be looking for.

Symptoms and settings are the same: car idles best when the mixture screw is all the way in, a very rich smell coming from the exhaust, I have a fuel pressure regulator installed (set at 2 psi). And these...

These are the ZFR5Ns that I should NOT have installed (I've now installed the UR5s). The one without the carbon build up has been cleaned, so don't let that distract you:

<img src=http://im1.shutterfly.com/media/47a1ce09b3127ccefe2c36d2399400000030O00EYtnDls3Zswe3nww/cC/f%3D0/ps%3D50/r%3D0/rx%3D550/ry%3D400/>

<img src=http://im1.shutterfly.com/media/47a1ce09b3127ccefe2d9014987d00000030O00EYtnDls3Zswe3nww/cC/f%3D0/ps%3D50/r%3D0/rx%3D550/ry%3D400/>

Keeping in mind these were the wrong plugs, and they only have 100-400 miles on them, do these offer any additional information? Also, does anyone want these? They're free, of course.

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J.R.
Tucson, AZ
'68 Dart 270 with a '76-'80 engine

Get some runtime on the correct plugs, then read (and/or post pics of) them. These will have been running much too hot to get an accurate reading.

Preliminarily, your symptom (won't idle properly without overly-rich adjustment) suggests a vacuum leak or an internal carburetor fault.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

I'll definitely post pics of the UR5s if this continues.
Isn't an all-the-way-in screw the leanest possible setting? Doesn't turning the screw inward reduce the flow of fuel? Like I said, I was under the impression my carb was wanting for more air, and that's why I planned on reducing the size of the pilot jet. This seems to corroborate that: "Less than 1 turns out = Go down on the primary idle jet" (the engine requires less fuel). I'm sorry to rehash on basics, but I'm concerned I've somehow got this backwards.

I should also mention that when I sprayed a burst of carb cleaner down the carb, it died instantly.

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J.R.
Tucson, AZ
'68 Dart 270 with a '76-'80 engine

Certainly is not running lean then.

Depending on the carburetor it can only take so much air without forcing more air flow via a turbo or supercharger. I think you are over looking a possible vacuum leak as Dan previously mentioned.

Go down on jet size until it idles between 1 and 2 turns out.

Did you rebuild the carburetor? Is it a reman?

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'73 Scamp (the girlfriend): 225ci super/6 2BBL conversion (Almost done!)
'90 Subaru, wagon (the wife): H4-cyl 2.2L

1977 Mercedes-Benz 300D, 5cyl diesel(For sale!)

It was a new Weber - one year old, now. Yeah, I'll do some more vacuum leak hunting today.

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J.R.
Tucson, AZ
'68 Dart 270 with a '76-'80 engine

How many turns on the idle speed screw? The Transition holes may be exposed below the throtle plate. Lower the idle speed and then adjust mixture screw. The weber has an Idle Air Bleed circuit. If this is dirty it will cause the idle and transition circuit to both be rich.

Then you don't know for sure if say the float level is correct. Or if the idle air bleed is clean or not.

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'73 Scamp (the girlfriend): 225ci super/6 2BBL conversion (Almost done!)
'90 Subaru, wagon (the wife): H4-cyl 2.2L

1977 Mercedes-Benz 300D, 5cyl diesel(For sale!)

So, yeah, I read this elsewhere several times, and I didn't understand what it was getting at until this afternoon. And because of this, as it appears you're hinting at, I just may actually be running lean. I backed both screws out and went up one primary idle jet size with no real results yet, but I'm more on the right track now.

I wasn't aware of this air bleed circuit you both mentioned, so I'll look for that as well. Today was the last day of my nine day vacation, so I'll follow up with you just as soon as I can spend some more time with my engine.

Thanks for the tips, gentlemen.

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J.R.
Tucson, AZ
'68 Dart 270 with a '76-'80 engine

You decrease idle fuel by turning the idle screw inward. The idle adjuster screw limits the fuel entering the throttle body after the main jet. If you lower the main jet you'll need to adjust the idle screw outwards to compensate for smaller jet. If your running rich and the idle screw is inward all the way and you increase main jet size it should increase fuel flow hence running richer.
Remember when the engine is idling the throttle plate is barely open thus its drawing miniscule air without fuel mixed.
You need to go down main jet size until you can back your idle screw out 1-2 turns...as I previously mentioned. That Weber 32/36 tune up guide also refers to this...

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'73 Scamp (the girlfriend): 225ci super/6 2BBL conversion (Almost done!)
'90 Subaru, wagon (the wife): H4-cyl 2.2L

1977 Mercedes-Benz 300D, 5cyl diesel(For sale!)

it's already running rich so if you spray a burst of "carb feces in a can" down the carb it's only going to suffocate the running condition.

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'73 Scamp (the girlfriend): 225ci super/6 2BBL conversion (Almost done!)
'90 Subaru, wagon (the wife): H4-cyl 2.2L

1977 Mercedes-Benz 300D, 5cyl diesel(For sale!)

If someone wants to stop me from repeating my point that the carb is NOT running lean then go ahead...

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'73 Scamp (the girlfriend): 225ci super/6 2BBL conversion (Almost done!)
'90 Subaru, wagon (the wife): H4-cyl 2.2L

1977 Mercedes-Benz 300D, 5cyl diesel(For sale!)