Triple guy's need some help

[240ZGL]

Running a 2.8 on triple Dels. Facet 2 to 4 lb. fuel pump, filter before the pump, 5/16 hose all the way to the carbs, no pressure reg, no return, Carbs were pro rebuilt . It has run hard for the past few months. Out of the blue it dies out past 3500 rpm on the freeway only. On city streets it still runs ok. I have change the pump, lines, and filter with no joy. It will not even run at 3000 rpm on the freeway. Any ideas ?

[Travel'n Man]

Start with a pressure regulator......IMO

[steve91tt]

When I had a similar issue I T-ed into the fuel line at the carbs and ran the new line up, out of the back of the hood and under the wiper blade. I put a fuel pressure gauge on the end of the line so that I could monitor my fuel pressure on the highway. If the fuel pressure stays steady then your fuel delivery system is not the issue. Are you sure it's fuel related? The ignition systems on these cars can give similar symptoms as you describe.

[240ZGL]

Ignition is Mallory w/ Pertronix 2. Fuel pressure is 2-4 psi, the pump is new. The old one was new too.I can here the pump running. Fuel system has no restriction. It's strange in that it runs fine on the street, but I hit the freeway and it just flat runs out of fuel. I'm only running 3000 to 3500.

[steve91tt]

The demands on both the fuel system and ignition go up as you load the engine up on the highway. It's not uncommon to have issues under load that don't show up while driving at lower speed.

[LeonV]

Fuel pressure is 2-4 psi, the pump is new. The old one was new too.I can here the pump running. Fuel system has no restriction.

And you know this because you tested it?

Sounds like fuel starvation to me, so test it as Steve suggests. This is easy. If that passes, then move on to ignition which may be a bit more tricky to figure out.