Engine cuts out over 55mph

[Malia123]

This truck wah having troubles running so my daughters in-laws father replaced the fuel filter and carb with a weber. there are a lot of hoses hanging. We found fouled plugs and bad wires so it was given a complete electical tune up. after the carb was changed the truck would run fine up to 40 mph, after the tune up it runs fine to 55mph. After 55mph the truck stumbles (cuts out) and the more fuel you give it the worse it gets. If you back it off to below 55mph it runs fine again. Anyone have any ideas?

[PEZi]

So you did connect all the hoses back up? And the truck runs fine below 55? or does it run fine below the rpm that gets it to 55 (what I'm asking here is if you were to try and floor it up through the gears it would literally run fine no matter what gear it was in up until 55?). Also, is this manual or auto?

[Malia123]

Answer 1: We are not sure if any of the hoses that are left off go anywhere now that it has a Weber on it. They appear to be for the emissions that the Weber does not have. The EGR is no longer hooked up either.
Answer 2: I'm now hearing that you have to gradually accelerate and you can get it to 55mph. This is my daughter in-laws truck and I have not driven it. If you try to accelerate to quickly in any gear it kicks and bucks. When you try to adjust the distributor it has to be all the way to the end of the slot or it won't run.

[PEZi]

Well this could get complicated not knowing the exact condition of the hoses and whatnot. But, it sounds like one of two things. The first one being that there is a hose unplugged somewhere that needs to be plugged... also known as a leak. It's not that the weber needs many hoses to run, but if there is one left open allowing for vacuum to leak, there is a problem. The other thing it could be is something with the timing. If the dizzy has to be turned all the way just to make it run, there is a chance either that the dizzy did not get put back on right (if it has ever been off) or that the timing chain skipped a tooth or was put on one tooth off (assuming it has ever been worked on).

Last, but not least, it could simply be a fuel related issue. If it's running a weber, it needs a pump that is in healthy condition and should most definitely have a fuel pressure regulator on it set to 3.5psi. Hope that gives you something to work with!

[Malia123]

Thanks we will look at all the ideas. This truck does make a lot of upper end noise, so timing does make sense. we will check for vacum leaks as well.