The carb float height specification or adjustment during cleaning & rebuild, new gaskets &c., is simply a bench setting to get it close. Once it is installed on the engine the "wet height" needs to be checked.

It is important during a Tune-Up or replacing a fuel pump that the fuel delivery to the carb is within specs listed in the shop manual, for both pressure and volume. Newly manufactured fuel pumps imported by the shipping container load have not been covering themselves in glory lately. It used to be we could purchase a new fuel pump from the usual suspects and get away with just installing it, "close enough". Not anymore. They are all over the place, and in some cases downright dangerous.

Your mechanic's vacuum gauge is also designed for testing fuel pump output pressure in just a minute or two, the engine doesn't even really need to be started, just crank the starter for a few seconds while connected to the pump or fuel line. But the engine should idle a few minutes with just the fuel remaining in the bowl.

The static output pressure should be 5.5 to 6.5 psi, more than this is not better.

If the output pressure is OK, then let it idle for a few minutes on level ground. Shut the engine OFF, remove the air horn, and take a look see, the fuel height (not the float height) in the bowl is how the carburetor is calibrated, a US Washington quarter is 29/32" or near enough and makes a handy "gauge", Measure from the machined surface at the top to the surface of the fuel itself. Adjust the float arm up or down as required to achieve the correct fuel height. If you are very careful the Autolite 2 barrel carbs can be observed at idle for fuel height.

It's possible all this has nothing to do with the engine cutting out at highway speeds. But this is how a Ford 2 barrel carb is setup and will eliminate mucho tuning problems and engine derangements.

 

This is really good stuff, thank you. I'm brand new to this level of automotive diagnosis; should I plug the vacuum in to the line between the fuel pump and the carb?

 

Awesome, thanks for this insight.

 

I blew through the filter and it's totally clear. I also pulled the line leading into the fuel pump from the tank and it flowed freely. Still pointing toward a bad fuel pump? Are there any fuel pumps available (not at the store/from overseas) that may cost more, but are reliable?

 

Just hook the vacuum gauge hose directly to the fuel pump outlet. Or wherever you find it convenient. There's no need for a T or any contortions.

See if you can find NOS or something made 25 years ago, maybe, if a new one is needed. Sometimes the problem there is how they were stored or rubber parts deteriorating. I wouldn't stress it too bad, just buy local, and be sure to measure pressure. If it's off spec take it back and try another.

I had to really crank the float down all the way with a replacement fuel pump, and it measured 8.5 psi, a couple pounds more than spec is a lot. No bueno amigo! That tiny piece of viton on the tippy tip of the inlet needle is the only thing preventing gallons of gasoline gushing over your motor if it gets overpressure. At least that's what it kinda looks like to me.

Anyhoo the Holley and Autolite 2 barrel carburetors as used by Ford are excellent, but one of the most important adjustments is giving it enough volume without excessive output pressure. Too much or too little fuel is bad. Fuel height in the bowl is also important, the entire carburetor is calibrated from the factory based on this.

See if you can scare up the Ford or Autolite carburetor manual(s) in PDF form online, and study them, there's all kinds of good stuff in them on theory of operation, for setup, and adjustment or calibration. There really aren't very many checks or adjustments, but every single one is really important.

If the ignition system is straight on your motor it should run real good when you're done with that carb.

 

Low voltage to the coil could also be the culprit. Measure the coil feed volts at idle. From the start I thought fuel problems , but now I think lack of fire power.

 

Put a hot wire on the coil and see what happens.

 

Replace any rubber fuel hose.
Old hose can look good but be bad on the inside with today's fuel.
Dave ----