I've got a 70 f100 with a 300 and I just rebuilt the carb two weeks ago and put a new fuel filter right before my carb and the reason I rebuilt it was because my needle and seat I presume were leaking even though my needle looked good and my float is also good but it was over filling the bowl and flooding and over flowing everywhere I rebuilt it two weeks ago and it hadn't done it since then I went out Friday night and sitting in the ole outback parking lot letting her warm up I head something weird so I rolled my window down and it wasn't running right and then sure enough it flooded it out and did the same thing tried hitting it with a block of wood to maybe free my float up thinking that might be the problem hung her wide open and cleaned her out and drove straight home and when I got home it wasn't doing it but sure enough i went to O'Reilly's to get a new dimmer switch tonight and cut across to harbor freight and it did it again then went though the drive thru and it did it again I don't know if the gas I'm using may have damaged the needle or something or being now everything is unleaded and it doesn't have it's lubrication properties anymore if maybe it's causing stuff to get hung up I don't know I'm just confused what I did wrong

 

You may not have done anything wrong other than maybe set the float level a little to high?
I know when I rebuilt mine on my 81 F100 there were 2 different floats used and 2 different ways the level got set, is yours the same?
I think I would pop the top off and recheck the float level and maybe set it a hair lower just for S&G.

The other thing I am thinking of what fuel pump you using, motor driven or electric?
If motor how old is it? There have been a rash of new pumps that have put out way to high of a PSI and overpower the float.
I know as I had one on a non-Ford that put out 18 PSI before I shut the motor off as it was pissing out gas from the bowl vent.
You may want to run a PSI test on the fuel system after the filter to see what the PSI is when it floods over.

When the top is off the carb for the float level check recheck the float for fuel in it. Is it brass or plastic?
If the PSI is at 5 or under when it floods then I say carb needs to be looked at closer or replaced.
You can find knock offs on Ebay that have worked pretty good for some of us at least mine has been good.
Good luck
Dave ----

 

dave has a solid point asking about plastic floats plastic's may look good but are not, as they tend to soak in gas, making the float sink when running,only way to be sure is weighing them new verses old, when i rebuilt them in the days we always found a new one or changed over the a copper one

 

I have a single brass float I tested it in hot water too I don't remember where it was set at but it doesn't make sense how it's on and off like this morning it's 18 out she started right up and I let her warm up and drove around with no problem it's a motor driven pump I presume it's OEM but I have no idea it was fine when I putted around all summer then it started doing it when I went to start it this winter to start messing with it again I might go ahead and put a pressure regulator after my filter just to be safe but it's so random I just don't know

 

brass/copper float,stock fuel pump you won't need a regulator, but there's a chance the float is going bad,try replacing it before going wild

 

I would also say no need for the regulator but I would run a pressure test to see if the pump is messing up.

I did have a new tank sender float that was brass that went bad a short time after install.
I have never seen a brass float once filled with fuel and flood a carb to then not flood a carb because it got empty?
Dave ----

 

I'll probably try and test my pump it's been fine all day but then again it's been well below freezing all day and yesterday and the day before it was high 40's and low 50's so maybe that has something to do with it

 

Knowing what the pump puts out, even. More so when the carb floods, is needed so you can rule out the pump and look more into the carb.
If part of an old rubber hose, todays fuel eats old rubber hose from the inside out, got stuck in a check valve of the pump and then gets un-stuck could cause issues where the PSI test would show it was a pump or not.

If it was not for testing the new pump on my non-Ford project I would have thought it was the carb as the project only runs once every few months and not for long times.
Dave ----

 

i have found a few brass floats developed cracks in the solder
i'm also with dave as the rubber hose causes more problems today than decades back with the 10 and 15 % grain in the gas

 

I'll check I have all new rubber hose on the two little spots it's not hard line and I have a filter in front of all the stuff that I'm not so sure how good it is but it ran great again today so I'm at a loss I think it's just trying to screw with me it's probably like let me die ******* it it gets to meet -14 tomorrow though so we'll see