1963 Carb Flooding Problem

[Seth McCulloch]

My early 1963 300 HP has a Carter AFB 3461S carb. I’ve been having an inconsistent problem with it flooding over. It will feel like the car is running out of gas, but in reality enough fuel is dumping in to the carb to kill the motor instantly unless the RPMs are kept up. Upon inspection, gas can been seen dripping out the sides of the carb on to the manifold. It appears that the needles are getting stuck “out” allowing fuel to pour in to the bowl regardless of the position of the floats. The easy remedy involves removing the air cleaner and tapping on the top/rear of the carb with a hammer to try to free up the needles. If this doesn’t work, the top of the carb must be disassembled to gain access to the needles so they can be manipulated.

The needles, seats, floats and float “axles” (for lack of a proper term) have all been replaced, some more than once. The float levels have been adjusted and I believe they’re in the right place. The fuel pump has been replaced too, thinking that perhaps there was too much fuel pressure. I can’t find a pattern as to what triggers the flooding, although it is more likely to happen during heavy throttle. Once it’s been “fixed”, there are no worries until the next random time that the needles get stuck.

Any help that can be suggested would be appreciated, or recommendations on who would be the right person to speak to / work with. Possibly unrelated note: there is also some (occasionally bad) hesitation when starting out in first. The engine will lug as load comes on. Stuff the clutch, try again, and it will get moving. I’ve got the PCV hose partially restricted and this seems to help somewhat.

Thanks,

Seth

[Clem Zahrobsky (45134)]

Re: 1963 Carb Flooding Problem

with the top off and upside down on the bench apply 5/6# of air pressure to the fuel line connection and use a soap solution around the needle/seat where it attaches to the carb top. i have seen that the gasket used there in carb kits have too large a inside diameter and cause a fuel leak there. check the "float drop" spec also

[Timothy Barbieri (6542)]

Re: 1963 Carb Flooding Problem

In addition to what Clem say's, make sure the floats don't bind in the body when they are moved up/down. What is fuel pump pressure, book say's 5 1/4 to 6 1/2? Hesitation is vacuum leak or acellerator pump circuit, be careful here because pump works hand in hand with float level, if the floats are set too low the pump will push air first and result in hesitation.

Do you have the proper gaskets and heat shield and did you plug the small heat slot holes in the intake manifold as this will make a huge difference in carburetor temperature and may make things a little easier to troubleshoot(you will be able to eliminate fuel perculation).

I am chasing my own gremlins with a 3461S but I believe my problem lies with wore throttle shaft so it's off to the carb restorer for me, I can't afford any more gaskets! Sorry for the long post, Tim

[Chris Davies (38924)]

Re: 1963 Carb Flooding Problem

Tim,

Is your throttle shaft bore wear giving you variable idle? Try this if you haven't shipped out the AFB yet.

Only the most inner length of the throttle shaft bore, directly under the fuel bowls, is a close fit. The outer portions of the shaft bore are clearanced 1/32" over. I fashioned my own bushing liners out of 0.015" thick teflon sheet and lined the outer ends of the bore in the throttle body. Now she comes back to the same RPM every time.

Cheap, effective, and no reamer required.

Chris.

[Timothy Barbieri (6542)]

Re: 1963 Carb Flooding Problem

Chris,

My problem with the 3461S is that the car idles about 750-800 RPM with the stop screw backed all the way out and butterflys closed. Can't get it to idle low (500 RPM) I have checked everything and had local carb rebuilder overhaul also. Vacuum at idle 18" to 19", car runs nice but spark plugs show black soot. I think there is internal vacuum leak (throttle shaft) and finding gas somewhere but just enough to make car run at that idle RPM so it must be slight.

Only other thing is that someone modified this carb with some hot rod trick for big cam and I can't figure out what was done. This is a swap meet carburetor but I can't give up because correct # and date.