I have a remanufactued OEM style carb. I was trying one last time to mabye passed emissions with the tired 400 none origanial motor. But it ran out of gas. Or so I thought. Everything is new. From the tank to carb. Fuel level, fuel pressure, Bla Bla. But it only runs with gas dumped down it. Or as much fuel as the acc. pump can provide. When it runs for a short time. I see no fuel coming out of the venturi's? And nothing seems plugged. Clean as should be with all new parts. I spent good money on this carb. because it is from a name brand. And it looks dang origanial for the one I will need for the 390 swap. I.E. stock pull choke and such. And yes the warrenty is long passed. It started after I changed the points and breaker plate. Yes it back fired a few times. But if I blew the power valve it should be running richer. I am way confussed.

 

have you pulled it appart yet to see if float needles are stuck? I guessing it's Holley?

 

It sounds like you have a very large vacuum leak.

 

Is fuel at least getting "TO" the carb ?

 

Yes plenty of fuel. I took the top off and double check float level.

 

I will try a cleaning it up. Putting back to together. And changing the base gasket to a insulator. If I can find one. But I would rather rebuild the 390 I found then do a intake set. And yes bad390ford it is a holley remanufacted motorcraft.

 

A hidden vacuum leak I found one time on my '72 was a bad brake booster line.If your brakes seem normal, prob nothing wrong there. Pump your brake pedal down to the floor, hold it and start the truck. It should come up as you hold pressure. Also make sure you dont have any vac hookups that dont have a hose or a rubber cap. Or this could just be a carb prob. yesterday put a Holley 4160 on neighbors '75 with a 460. ran great right out of the box.

 

Brake booster is already blocked off. It whent bad first test run. I might try and do a test run on a 390 I picked up. Using the carb. Then I will know for sure. I even tried the old carb. on the 400. And no luck. Same thing. Will not suck gas.

 

Have you tried unhooking the gas line from the carb and seeing if the fuel pump will push a good stream out of it? Checked the incarb filter where the gas line screws on? Once had this prob and found the gas tank pickup was plugged. When you check the fuel line, I find it better to let the gas squirt into a 1 litre pop bottle so it doesnt get a chance to spray all over. Or hook a piece of hose to the line and get it away from the motor.

 

you mentioned it will not "suck gas". The fuel line is pressureized at 5-7 lbs when the motor is turning over. You might just have a stuck float needle seat, or bad float adjustment. When I get a carb prob, I just usually go ahead and take it off and rebuild it after letting it soak in a bucket of carb cleaner, hose rinse off and air nozzle blow out, before putting it back together with a kit. OBTW, I usually buy a new float with the kit and do it all.

 

All that is good. It must have a bad intake leak. I see tons of silicone on the intake. Probely more bad repair work by the previous owners. That has been my only problem. Too bad. Turns out it is a true 53,000 mile truck. Too bad they dumped the origanial 390/C6. And then let it sit for 10+ years!