CarZombie 25 Report post Posted April 12, 2018 1970 with 351 Cleveland motor (4 barrel heads), AC, with a Autolite Model 4300 Carb. It was rebuilt in Mid-2014 and was working fine up to Late Dec of 2017. It was rebuilt using a Daytona Parts kit. I choose them because they specifically said there stuff was ethanol compatible. Last 3 times I tried to drive the car, in Jan/Feb 2018, It would not idle or drive worth a damn. It appears to be running way to rich. Both with choke and with out. Car was driven about 1500 miles in Dec. Annual mileage typically runs about 1200 miles a year. I know I should drive it more. Questions: 1. How long are carbs lasting between rebuild in this age of ethanol? 2. The guy who rebuilt and tuned the carb said the float was taking in gas and suggest finding a new one. Of course, I keep putting it off. Does any one know of a vendor selling floats for this carb? 3. I have used fuel stabilizers is gas power tools, but not in my car. Has anyone used them in their Mustang and did it made a difference? Thanks. Quote Share this post Link to post Share on other sites
CarZombie 25 Report post Posted April 12, 2018 Mike's Carburetor parts has a repo for the float: http://www.carburetor-parts.com/Motorcraft-4300-Float_p_3527.html Found it by using Duck, Duck, Go Only found one other list for this float and it was about twice as much. Still would like answers/opinion on other two questions. Quote Share this post Link to post Share on other sites
1969_Mach1 333 Report post Posted April 12, 2018 Will it not idle because it is flooding? Or will it not idle because an idle circuit is plugged? You can easily see if it is flooding by CAREFULLY looking down the carb. Even after the engine is shut off, if it is flooding you will see a bunch of fuel down the venturies of the carb. NPD has floats for the 4100 series carb, is that the same float? Three years is a long time to go between rebuilds with todays fuel, in my opinion. More so, on cars that are not driven much. As the fuel in the carb evaporates it leaves residue that builds up over time restricting passages. I'd say, freshen the carb once a year to avoid any issues. Quote Share this post Link to post Share on other sites
mqu02 30 Report post Posted April 14, 2018 If your float is taking in enough gas, your engine will probably be running richer, and you might not see it with the engine off (because the engine isn't pumping fuel anymore). The fuel height in the bowl helps determine how much fuel the engine gets. A higher level runs richer, and if it is way too high it can pour in through the vents (assuming the needle/seat is malfunctioning as a result). On Holley's, a blown or malfunctioning power valve can cause them to run rich, but I am not that familiar with a 4300 so I don't know how common that is with that model. Also, you shouldn't have to be rebuild carbs every 3-years, even with modern fuels. In fact, most fuels today leave less residue behind than fuels from days gone by. I have a 4100 on a 289 that has at least 15 years since its last rebuild, it isn't driven that often, and still is easily one of the best running carb'ed engines I have ever been around. Quote Share this post Link to post Share on other sites
ray1970 88 Report post Posted April 16, 2018 I am not familiar with the 4300 carb. But if it has foam floats and not brass YES they can saturate and start to sink over time.(rich) The new fuels due leave the carb. looking clean. The problem is it corrodes the jets......Over time they just keep getting smaller till there is almost no jet flow.. (lean) I have yet to see any magic additive that works....They do sell a lot of it... Quote Share this post Link to post Share on other sites
