Classic Mustangs (Tech) Technical discussions about the Mustangs of yester-year.

does carb float adjustment require idle mix adj?

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Old Jun 1, 2009 | 03:23 PM
  #1  
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Gun Jam
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Default does carb float adjustment require idle mix adj?

hello here is a quick 1,2,3 story of my current "problem"

1) installed A/F ratio gauge got 12.5 idle reading when warm

2) carb inlet needle sticks causing serious flooding clean and reassemble

3) readjust floats which had been messed with a long time ago. They were hanging lower than the 1" recommended...I readjusted them (without pressing on the inlet needle) so they hung at the recommended 1" Normally I would have let sleeping dogs lie but during hard turns the engine would die so I figured I might as well have a shot at fixing that issue as well.

4) reinstall carb

5) test drives shows no flooding and runs fine under power. At idle when warm engine runs like crap and A/F meters climbs past 20 then indicates LEAN run. Pulling choke makes car drivable and forces A/F back to around 13 .

6) Checked for vac leaks using carb cleaner and found none

7) Im guessing that adjusting the floats caused idle mix to change...Since I have A/F gauge should I just zero both idle screws then back them out 3 turns and start car and adjust until A/F reads 13 to 14?

What do you guys think?

-Gun
Old Jun 1, 2009 | 05:32 PM
  #2  
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2+2GT
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The difference should be slight, but you'll have to adjust the idle screws. EIther way, the procedure is the same.
Old Jun 1, 2009 | 06:09 PM
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What kind of A/F ratio gauge did you purchase?
Old Jun 1, 2009 | 06:10 PM
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I adjusted the floats just now very carefully so they sit at 7/8th inch fully closed and hang 1" when fully open....It idles like crap and A/F still indicates an mixture leaner than 20 with idle screws at 2.25 open...fully opening idle mix screws gets me down to 16.5/17 pressing the gas causes an instant lean condition/ hesitation then it picks up fine...

Damn it there must be a small vac leak that I can't find with carb cleaner...Ill try replacing the base gasket and see if that helps

-Gun
Old Jun 1, 2009 | 06:13 PM
  #5  
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Gun Jam
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I got this setup
https://mustangforums.com/forum/clas...io-instal.html

So far its paying for its self quite well....
Old Jun 1, 2009 | 06:41 PM
  #6  
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Replaced base gasket with no improvement....

What am I missing?...help

-Gun
Old Jun 1, 2009 | 08:35 PM
  #7  
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Are you sure you didn't get trash in the metering system? Even a very tiny piece of garbage can block the idle passage. Also check for dirt in the idle air bleeds.

Is it an Edelbrock? I've found they're EXTREMELY sensitive in the metering circuit to trash. You might have to unscrew the booster assembly and pull the system(it all comes out as 1 piece, booster, emulsion tube, air bleeds, everything). Spray it out really good with brake cleaner, put it back together.
Old Jun 1, 2009 | 09:28 PM
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its a carter afb I think its the same thing as the edelbrock 1406.... You gotta be right dude there is nothing left...I guess ill get busy...again

Thanks

-Gun
Old Jun 1, 2009 | 11:31 PM
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67mustang302
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Make sure the fuel pressure at idle is around 6.5psi as well
Old Jun 2, 2009 | 01:01 AM
  #10  
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Yeah I have 6.25 psi constant

you were right man it was just like you said. I pulled that sucker out and there was a piece of something hanging out the end...probably the same POS that was blocking the inlet needle I cleaned all the tubes on both sides with a narrow wire and carb cleaner stuck it back together and got 11 to 12 A/F right off the bat

so I drove it around until warm then zeroed the needles and started at 2 turns and adjusted till I got 14 /15 at idle then I drove it around and it was working awesome then on the way back it leaned out to 17-19 and stated running like crap...I was like **** not again.

I then figured maybe I could dial it back so I gave the needles a about a 1/3 turn rich and bam it was right on the money at 14/15 again...I figured that was totally acceptable... I think its fixed unless it starts to lean out again im set!!

Thanks for your help

-Gun
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