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Motorcraft 4 Barrel Carb |
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FSJunkie
AMC Addicted Joined: Jan/09/2011 Location: Flagstaff, AZ Status: Offline Points: 4741 |
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Is any body else's 4300 particularly persnickety abut it's idle mixture setting? My emissions sticker says to adjust the idle mixture for a "40 rpm lean drop" and it runs fine if I do that, but if I ignore that sticker and set it to a "best idle" fuel mixture........woah, boy it is not happy!!!! It'll flood rich, bog, and even stall if the fuel is sloshed at low speeds, such as while driving over a speed bump at an angle or turning into a driveway. I mean it will flood and stall in the middle of an intersection and try t get you killed if you set it to a best idle mixture. Follow the 40 rpm lean drop though and it's happy as a clam. I know some carburetors that lean or flood on really hard maneuvers like hard stops, but it take a pretty strong lateral g-force to do it. I've never seen one this sensitive. I have inspected the float, needles, and settings more times than I can say and this car has always done this, ever since it was new. I know because it's been in my family ever since it was new. I'm wondering if it's just me experiencing this... Maybe there is a reason the police duty 401 used a special hinged float?
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1955 Packard
1966 Marlin 1972 Wagoneer 1973 Ambassador 1977 Hornet 1982 Concord D/L 1984 Eagle Limited |
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PHAT69AMX
AMC Addicted Joined: Jul/07/2007 Location: West Virginia Status: Offline Points: 5903 |
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The 4300 is a wonderful carburetor... no troublesome secondary Venturiis to worry about...
Just strait through secondary passages with boosters and an off-center air flapper valve... So much better than a Holley with actual secondary Venturiis & Boosters to react to signal, atomize fuel. Edited by PHAT69AMX - Oct/22/2021 at 9:54pm |
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Metman
AMC Apprentice Joined: Nov/05/2018 Location: Newtown Sq, PA Status: Offline Points: 53 |
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Just to ask.. Is there a rebuild kit for the 4300 that folks like? Thinking about reinstalling the original 4300 on my 1972 360.
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1972 Javelin/AMX
1960 Nash Metropolitan 1963 Studebaker GT Hawk 1956 Cushman Eagle |
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ramblinrev
Moderator Group Joined: Dec/28/2008 Location: Wisconsin Status: Offline Points: 11463 |
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Any fresh kit should be fine. |
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74 Hornet Hatchback X twins (since 1977)
62 American Convertible (still worth the $50 I spent in 1973!) AMCRC #513, AMO #384 70 AMX 360 4-speed (since 1981) |
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scott
AMC Addicted Joined: Jul/10/2007 Location: Wildwood Pa. Status: Offline Points: 3498 |
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I used a Walker kit # 15410D about 6 months ago. It came with the good blue accelerator pump cup. I bought an extra kit at the same time, so I can say I would use that kit again. Don't use a black pump cup.
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"Prolly" is not a word.
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S Curry
AMC Addicted Joined: Aug/16/2012 Location: Iowa Status: Offline Points: 598 |
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Maybe I'm deaf dumb stupid and blind. I collected about 3 4300 Autolites for my 70 AMX. After 4 kits at about 40 bucks apiece, Helicoils for the screw in the base that was stripped out....and an engine fire after splitting a fuel line and not catching it after removing the carb after a dozen times or more.....I bought a Holley 600 vacuum secondary return.. was $205 including shipping. Got it in 2 days. Put on, engine started right up and I HAVE not laided a screwdriver on it for the last 5 years..not even idle.....maybe I got lucky....damn it starts and runs good....
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SC
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Sonic Silver
Supporter of TheAMCForum Joined: Nov/23/2011 Location: East Tennessee Status: Offline Points: 7901 |
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PHAT69AMX
AMC Addicted Joined: Jul/07/2007 Location: West Virginia Status: Offline Points: 5903 |
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Sonic Silver, Summit "4010" holley clones that are silver or the newer Summit "Max Performance" 4150 clones that are black?
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Sonic Silver
Supporter of TheAMCForum Joined: Nov/23/2011 Location: East Tennessee Status: Offline Points: 7901 |
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Trader
AMC Addicted Joined: May/15/2018 Location: Ontario Status: Offline Points: 6749 |
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The problem may be that finding an old core that has not been corroded over time may be a challenge for many. The 4300 aluminum was not at all ethanol resistant and will pit and corrode if this fuel sits in it. Just had one apart the other day were the power valve was sitting looked like a nice O-ring grove was machined into the bore. Pitting everywhere you could see, so likely pitting everywhere you cannot also.
The owner was going to look for a replacement as I didn't think this could reliably be rebuilt. The 4300 did not look as bad as this:
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