Well, I can't say for certain if it is the carb. I have a holley single barrel 1904 on it, as far as I can tell. It idles and revs beautifully, however, when I am on the road it is a different story. Whenever it is under load, it wants to fall on its face. Example. If I am driving down a flat road, and am using 10-15% throttle, I can go all day long with no problems. If I encounter a hill and give it more gas, 20-30 seconds later, it bogs down and completely falls on its face. It is a straight six, and I seem to be getting plenty of fuel pressure. I have broken the carb all the way down and cleaned it extensively...no luck. I have a very slight fuel leak from the fuel pump, but it is a very slight leak...like a drop every 15-20 minutes. I took the fuel line off the carb and it seems to be pumping gas really well at idle. Could the vacuum of the pump be squeezing the old, soft rubber together to cause a blockage? Could the pump just not be delivering enough fuel for the motor when it is under load? I am going to get a fuel pressure gauge this weekend to see for sure. To me, it seems that the fuel in the bowl is simply getting used before it fills itself again. Could there be a problem with the float? It seemed fine when I cleaned it and it moved freely. Could this be a jetting issue? I was thinking of boring out the jet slightly to allow more fuel to come in, but I want to see some fuel pressure numbers first. Sorry for so many questions, I am used to mapping out fuel injected motors and carbs are fairly new to me, oddly enough.

Thanks!

Chris

 

Check the fuel filter and fuel pump pressure with a gauge, at a idle it can seem fine but it`s a much different story when more fuel flow is required.
After that check the float level on the carb.

 

Agree with fomoko1 also any idea what kind of shape the tank sock is in? The fuel pressure gauge will be the bottom line on what is coming to the carb. after that you might have to find some with a tailpipe sniffer to see what the air to fuel ratio is under load. 14to 1 is about what your hunting for.

 

The guys who answered are giving you good advice. Don't go drilling. If you are getting good throttle response in that 20 seconds before it craps out, you don't have a jet problem.

The best way to troubleshoot is to "rule out what the problem isn't". Only fix or change one thing at a time until you get it solved. It doesn't sound like a difficult problem to solve.

Good Luck.

 

Not sure if this will help, but when I first got my truck I had a similar problem. Turns out the previous owner had the fuel flow cutof valve at the gas tank turned almost off. Just enough to provide gas for idle and city street driving but as soon as I put a load on the engine the fuel line starved.

 

I will definately have to check this out! I am going to replace the fuel lines and see what kind of pressure I am getting, as well as checking for any debris I may have clogging up the fuel route.

 

"Holley carb giving me problems"

I wish I had a dollar for every thread with this title!

I'm going to start looking for a new kind of carb for my truck, or else EFI.

 

As original, these years of trucks have a glass bowl inline fuel filter. The filter itself is made from a ceramic material and clogs up. At speeds up to about 25MPH, everything is normal, give it the gas, vehicle bogs down. Most ppl never clean or change the filter, which is available from NAPA. The filter top has a metal cover and bale with a "star" nut on top. Unscrew the nut, the cover can be removed. Don't overtighten the nut when after replacing the filter. Just about every car/truck made from the 1930's through the mid 50's used these inline filters. It was "state of the art" once.