Hey Guys/Gurus,
I recently got a Holley 350 CFM 2 barrel carb to replace my badly leaking original carb (not sure if it's autolight or what). The problem I'm having is that the carb feels like it's running out of gas in fact it seems to be running out of gas but for the life of me I can't figure out why. I'll give you a run down of the problem and hopefully someone can help me out.

The Holley carb that I installed had to have a new fuel line run because of the way that it comes into the passenger side of the carb versus the way the old carb fed into the front. I had to make a whole new line out of 5/16 brake line and used a new plastic see through filter to make sure that I had no problems with dirt getting into the carb. Well after getting everything put together I went down the road but the truck seemed to be running out of gas. I popped the hood and looked at the fuel filter and it barely had any gas in it. I watched it for a minute or 2 and I could see it start to trickle back in so I closed the hood and took off back to the house. When I got back the truck was about to stall and after popping the hood again, the filter was almost dry. I started to think that my fuel pump was on the way out so I went and got another one.

I put the new fuel pump in and start up the truck, same condition. The filter fills up and then after a test run the filter gets sucked dry. I go and get another fuel filter thinking there's something wrong with it but same thing again.

Here's what I don't understand, I took off the line at the fuel pump and cranked it a couple of times and gas comes out with enough pressure to fill the filter with like 2 cranks, I disconnected the fuel line at the fuel filter and it has enough pressure to completely coat the engine bay (what a mess that was). But if I put it back on the fuel filter it won't fill it up. It's like there is pressure coming from the carb side of the filter pushing against the fuel coming into the filter from the pump. I wouldn't think this was possible but if I take and clamp off the line from the pump and crank the engine, the gas starts to pump out of the fuel filter back towards the pump. What could be causing pressure inside the line to make the fuel pump stop and cause the fuel filter to run dry? The truck will idle fine but if you put a load on it the filter just dries up.

I'm really stumped on this and if anyone has any ideas and suggestions on what to look at, it would be greatly appreciated.


Bill

 

The float or needle might be stuck and is not letting the gas into the carb fast enough. Or you need to adjust the float level.

 

Is the carb used or new/Holley reman.? It does sound like an improper float level.

 

It's a Holley that I got off of e-Bay, it's supposed to be rebuilt according to the seller.

I played around with it again and if I set the float (wet setting) lower than where it's supposed to be I don't have a problem with the fuel filter filling up but I get a miss at higher RPMs. If I set the float level again to be at the bottom of the sight hole threads then it doesn't miss but then the fuel filter runs dry. I'm wondering if there is a happy medium but why haven't I found it yet?

After reading some tech tips on the Holleys, once you set the float level it says to adjust the mixture screws to get the best idle and then you should be set. Are the Holleys that tempermental to all of these things?

I have another question about it, The old carb sat on a spacer that went between the old carb and the intake. The spacer has a vacuum port on it for the PCV hose and the new carb does too. I plugged the carb vacuum port and then kept the hook-up betweeen the spacer and the PCV intact. Should I plug the spacer and hook the PCV directly up to the Holleys vacuum port? I didn't think there would be a problem since they are both vacuum ports and either one of them would connect back to the PCV.

Thanks for the inputs so far guys, just keep them coming so I can get my truck back on the road.

Thanks Bill

 

The carb won't work right with the fuel level to low. It will run lean. It shouldn't matter which port you hook the PCV to. I wouldn't worry to much about how much fuel you see in the filter. I have a clear filter on mine and I don't think it is normally full and the engine runs fine.

A Holley is no more temperamental than any other carb. I wouldn't claim it is the world's finest carburetor. I have four of them in the shed and a Carter AFB on my truck. They all need to be adjusted and tuned to the engine to work the best.

If the float bowl is running dry I would check the fuel delivery at the carb. If that was good I would pull the needle and seat and check it.

Could the fuel filter be in backwards? I think most have the inlet and outlet marked.

 

Adjust the fuel level to just below the sight plug hole.

 

Here's some more of a break down of what I found. When I got the carb off the guy on e-bay, it didn't come with any type of fuel filter built in. The size of the line going into it was way bigger than anything I could use so I went to the parts store looking for an adapter or reducer. They hooked me up with an adapter that brought it back down in size for the 5/16 inch brake line I was using from the fuel pump. Well I took that fitting off and looked at it more closely and it was actually reducing down the line smaller than the brake line so i figured that it was causing too much of a restriction thus putting more pressure inside the carb than was needed. I went to speed shop that works on Holleys and showed them what I have and they gave me a fitting that threaded into the carb and had a nipple on the end for a rubber hose to the fuel filter. I hooked it up awhile ago but now I cant get the engine to start. I probably have to adjust the float again since it's probably been pushed all around the place with the extra pressure.

Needless to say it's really racking my brain right now because I cant get it to start at all. I've got the fuel filter in correctly with the arrow pointing towards the carb. I just checked the timing and I have it on TDC and I keep trying to get it to start and it will attempt to but it still keeps cranking. I've probably flooded it out so bad now that I'll let it sit over night and try again in the morning.

Thanks for the help so far guys and I'll post something tomorrow if I can figure it out.


Bill

 

I finally got the truck running right with the Holley carb I got. I had to go to a speed shop and I bought a new rebuild kit, clear sight screws and a 1" spacer. ( I wasn't happy with the Ford original one). I installed a new float needle and sealed it up with the new nylon washers that came in the kit. I couldn't get the truck to start at first and after I pulled the plugs I found they were badly gas fouled. After swapping them out, I got the truck to idle and then I installed the new sight screw and got the float set till gas just barely comes out of the hole when I rock the truck back and forth. I'm pleased so far with the throttle response and I need to get a pertronix kit and coil to replace out the points in the dizzy. But the miss at high RPM is gone and it's not drying up the fuel filter under load so all in all I'm pleased. Tomorrow I'm gonna change the oil and get that out of the engine because I'm pretty sure it's got a load of gas in it also.

Thanks to everyone that threw ideas my way and I greatly appreciated it.


Bill