Guys ive rebuilt a few carbs over the years and generally do a fair job BUT irebuilt this AFB (got my kit from carbking) and it starts and runs fine but i cant get it to idle smooth unless i back the mixture screws out about 3 turns ,,,,,,,ive messed with it till i sick of it and decieded hell if it idles good with the screws out 3 turns let it be,,,,,,,,,, BUT now i find if i let it sit for two days i have to crank it over a lot (it is bleeding down),,,,,,,,,,,,,, SO now i think my two problems and related BUT i cant figure what to look at Any ideas would help thanks pete
How about some more info about exactly which number AFB it is and what kind of engine you have it on. Fuel evaporating out of the bowl in a couple of days is typical--especially if you have an aftermarket open air filter on it.
OOPS sorry the carb is a 3826s and is the correct carb for my car which is a 65 skylark 300/4 auto the car is bone stock except for duals and point less ign ......as for air cleaner it is org and the 2 barrel i took off would start up right now after 2 weeks thanks pete
Pete, if the idle screws like to be out that far (it is too far), but by all means keep the carburetor happy :TU: If it runs well there, and you don't get the off-idle hesitation often associated with the idle screws out too far, leave it. The other problem, as Brian suggested, is probably fuel evaporating from the bowl. Pretty common problem in hot weather with modern fuel, especially with the AFB. The Rochester two-barrel is less susceptible to evaporation, as there is a cushion of air between the bowl and the intake, whereas the AFB bowls sit right on the intake. I have a pair of AFB's on my 390 shop pickup. On a 100 degree day here in Missouri, the fuel will be gone (bone dry ) in about 2 hours after engine shutdown. I installed an electric fuel pump many years ago. End of problem. Hope you liked the kit. Jon.
Jon thanks for the input ........... im really worried that the gas is leaking into the cylinders and then down into the oil thats my major concern....i do notice also that if i shut it off and then restart it 10 minutets later if acts like it is loaded up( have a spacer plate under the carb as you sugggested ) and it doesnt die or bough at all thanks again for the input THE CARB KIT WAS GREAT pete
The only internal problem I have seen cause the symptoms you have is if you have the wrong gaskets on the venturi assemblies. If you look closely, there are different ones in the kit--they look almost the same, but the holes are in slightly different locations on the different ones. If you have the wrong one on there, fuel will leak around the gasket and drip into the intake. The first time I built an AFB about 15 years ago, I made that mistake. As for loaded up when you restart after 10 min, I have the same problem on my car (mine is a '65 special 300 4bbl. 4-speed car). I cured it by putting on one of the filters with a return line to the tank (like is on the cars with factory Air conditoning). What happens is the heat from the engine makes the fuel in the filter/line go up in pressure and leak past the needle/seat on the floats. The fuel level then goes up too high in the bowls and spills over into the intake. Having the return line from the filter to the tank fixes that because it gives the fuel/air a place to expand to other than past the needle/seat into the carb. I think it was basically a factory flaw in the whole setup. Only happens on non-Air Condtioned cars.
OK good my car is an air car and does have that style filter but it is an old one so ill get a one and try it thanks pete
Attached is a picture of the gaskets for the secondary venturi assemblies. As you can see, the two on the left are almost the same, but the hole spacing on the smaller holes is closer together on one of them. The '65 300 carb. uses the one in the top left. If you use the one on the bottom left, it will leak fuel by the gasket and it drips down onto the throttle plates.
Thank you sir wow there isnt much differance well that on my list of things to do ,,,...i will let you know if thatt was my problem thanks again pete
Pete - I can save you the trouble. If you remember, there was only one set of primary, and one set of secondary gaskets in the kit. We don't sell generic kits with lots of gaskets. All of the gaskets are correct, to eliminate guesswork. Jon.
OK JON one question im thinking of removeing the carb placing it on a flat new piece of cardboard connecting a hose to it and filling it with gas ...then in a hour or so check it if i find a stain maybe add coloring to help locate leak,,,,, how does that sound to you????? thanks pete
Pete - I still think your problem is evaporation of the fuel caused by the volatility of todays fuel and the heat from your engine; but if you want to try removing and testing as mentioned in your previous post, it won't hurt anything except posssibly the mounting gasket. Jon.
I would leave it on the car to test it. Run/drive the car and get it hot, then immediately after you park it, take off the air filter, and pull the accelerator pump rod off the pump arm (so you can open the throttle plates without the pump squirting in fuel). Then open the throttle plates and look down through the throttle plates into the intake using a bright flashlight. If it is leaking fuel into the intake, you will be able to see it within 5 or 10 minutes. If it is a bad leak, you will see it immediately. You will also have to stick a screwdriver in the secondary side to hold the counterweighted air valve plates open so you can see down in there.
