I have a 1979 f150 that has been sitting for many years.After everything short of an engine rebuild i got it running very nice except at idle.It has a 351 windsor with a 2 barrel motorcraft carb.I am unfamiliar with this carb.I cleaned the snot out of it and rebuilt it,simple enough.The primaries drip at idle and after the truck gets warm and sits for a few minutes the float bowl emptys itself into the intake after the truck is shut off.Carb has the 2 stage power valve and i have adjusted the float at least a 1/4 of and inch lower than spece.I have lowered it 4 times with no improvement.Its has a fiber float not brass and it is the long float.I have set float wet and dry.No improvement.With carb on bench and bowl full no fuel comes out fuel inlet and i cannot blow through needle and seat from outside carb when it is closed.I have removed gas cap and checked tank vent to make sure tank was not pressurizing.No improvement.Power valve seems to hold vacuum by mouth and all proper parts were installed from carb kit.Carb is venting and there are no vacuum leaks.I have the 1 inch aluminum spacer and the fat gasket under carb.Ive rebuilt my share of carbs but like i said this motorcraft is new to me.Ive got to be overlooking something but i cant figure out what it is.Any suggestions would be greatly appreciated.

 

Hopefully you're gonna get a lot of suggestions on this.

So,,,,,,, how about we start here,
1. Could you be working with a heavy float that sinks instead of floating. The cure is either a new float or a brass one for that particular carb.That was a common problem with "Nitrophyll" floats (someday I gonna learn how to spell that!)
2. Using a can of carb cleaner or brake cleaner with the "soda straw" and work back from the primaries and trace the path to how the fuel gets to there. It may shed some light on where the problem lies.
3. It has been a while, but I believe you could run the engine with the top section off that carb and observe the float at work. I wouldn't attempt that unless someone can confirm that procedure, It's a little too far back to remember.
4. Did you check all the parts that you changed for being an exact match?

 

Ive been thinking about the float the last day and a half.Ive stood there and had a couple beers and watched it and it doesnt let fuel out.Im heading out to the shop now and im going to take top off carb and see if i can run it.I think i might be able to.Thats a good idea,i didnt think about that.Im also going to order a new float.I got this truck free and its a nice solid desert truck and i dont have much in it already.Ill post my results.Thankyou very much for the reply.Ill try the other steps if float doesnt work.

 

I put in a brass float and set it a bit lower than previous float.Ran truck at idle awhile and it still dripped a bit.Shut the truck off and let it sit awhile and bowl didnt empty out.I left carb on and removed air horn and fuel level looked good.I drove it down to work a few miles and let it sit about 15 minutes and it still didnt empty bowl and fired right up.Drove it back home and let it sit a few minutes and it emptied bowl into intake.Im at a total loss.

 

I will check my info and see if there is anything I might suggest.
Can you refresh my memory some, is the accelerator pump on the bottom or the side of the float bowl?
On that note is there a check ball missing in that system?

 

If this is the old shoebox (or the holley version of it, also), the accel pump is on the side, and there is no check valve.
However, one other thing sticks in my mind, though it doesn't help with the dripping primaries; have you checked the power valve? They were forever going bad and the dual stages were the worst.
On another note, this reminds me of a very similar problem I had years ago on a truck with the same powertrain. I rebuilt the carb, and it dripped, ran rich, etc. I found that I hadn't blown out an air passaged well, and that caused it.
Also, did you see any warpage or possibly cracked anything (you'd have to look really closely, as I'm sure they're not easy to see).

 

Dont see anything wrong.I will get out the magnifying glass.Thought about the pwer valve.It is a 2 stage.Gonna pull it apart again tomorrow and order another valve and blow it out again.Its getting irratating.

 

Yes it is the half a holley 4 barrel style 2 barrel carb.I know its something stupid im missing.

 

On the lighter side,
If it is something stupid I should have guessed it by now !!

 

Greasemark may be on to something,
There are anti-siphon passages to prevent siphoning and that passage could be blocked.