Bog/rough running at 70mph

[dmjlambert]

Under the cab there is probably a short piece of fuel hose that goes between the hard line from the gas tank to the hard line on the frame. And at the engine there is another short piece of fuel hose that goes from the hard line on the frame to the fuel pump. You probably replaced the one going from frame to the fuel pump when you put in the engine. I suggest inspect the one under the cab and if it has not been replaced before you may need to replace it. If it is very old or maybe original be careful because it can crumble in your hand when you give it a squeeze and the gas will siphon out of the tank all over the floor or ground. Since you are going to be removing the sender to put a new sock on it, it means you will be disturbing the hard line that goes from the tank to under the cab and will cause movement at the fuel hose under the cab. The truck original fuel hose was not rated for gas with ethanol, but make sure your new one is. Since ordering a sock you may also need the fuel sender rubber grommet for when you put the sender back in the tank.
I'm not 100% sure on the fuel hose arrangement for 6 cylinder because I have an original V8, so my info may not be completely accurate.

[Awann99]

Originally Posted by dmjlambert

Under the cab there is probably a short piece of fuel hose that goes between the hard line from the gas tank to the hard line on the frame. And at the engine there is another short piece of fuel hose that goes from the hard line on the frame to the fuel pump. You probably replaced the one going from frame to the fuel pump when you put in the engine. I suggest inspect the one under the cab and if it has not been replaced before you may need to replace it. If it is very old or maybe original be careful because it can crumble in your hand when you give it a squeeze and the gas will siphon out of the tank all over the floor or ground. Since you are going to be removing the sender to put a new sock on it, it means you will be disturbing the hard line that goes from the tank to under the cab and will cause movement at the fuel hose under the cab. The truck original fuel hose was not rated for gas with ethanol, but make sure your new one is. Since ordering a sock you may also need the fuel sender rubber grommet for when you put the sender back in the tank.
I'm not 100% sure on the fuel hose arrangement for 6 cylinder because I have an original V8, so my info may not be completely accurate.

I put the new Fuel filter and sock on. The sock looked fine. There was some gunk around the metal part where it slid on the line. The filter had gunk inside of it.
My sending unit was replaced about 4 years ago. I ran rubber fuel line from the sending unit to the metal line under the cab due to the original line breaking. Now that y'all have brought up the collapsing issue I'm going to replace that with a metal line and set it up like it would have been from the factory.
I haven't taken it for a spin yet but progress is progress.
Posted via Mobile Device

[Awann99]

I meant to update this a while ago but better late then never. The fuel filter helped the truck. But it is still having that stumble at 60-70. I advanced the timing to around 14-16 before tdc and it ran better at high speeds. I'm thinking maybe the vacuum advance may be not working now. Still a strange situation. New fuel lines are on order as well.

[Grumpy old man]

The Small block Chevy engine that built America using 50+ year old technology in stock form is one of the most basic engines to survive 50+ years and still be a favorite engine in many muscle cars and trucks , They will run with gas that smells like turpentine , 5lbs of oil pressure , No air filter , Vacuum leaks , points ignition , and keep going ! Add an HEI and good maintenance and you've got a runner , Always start with the basics fuel/ compression and spark .

No computers needed !