I have a 71 chevelle 350 with 4bbl. The fuel tank has 3 vapor lines. This is a new engine for the car (about 10,000 miles - less than 500 in my car). 1 hour into a long drive i experienced loss of power at 60mph then at less. Had fuel filter and fuel line blown out thinking they were stopped up. Ran fine for about 30 min then completely quit running. Removed tank last night and fuel seems clean - no rust etc. I dont understand how the vent lines, fuel cap etc work to create proper pressure in tank. Is tank not getting air and creating a vacuum?

Try loosening the gas cap next time this happens. If you hear the air whooshing into the tank, then you are creating a vacuum (and could collapse the tank!).

I have fixed this the WRONG way on my car- I drilled a tine hole in the gascap to let air in.

-Bob Cunningham

Have you checked your fuel pump? I'd connect a guage to the line up by the carb and make sure it is putting out a minimum of 4 - 7 psi at cranking RPM, and that the pressure is steady. The needle should not be bouncing around the dial of the guage. Also, it should hold pressure for a few moments after you stop cranking the engine.

This happened to me a couple of times, ended up being a bad fuel sock in the tank.

Thanks everyone, removed the tank, drained the fuel, checked for rust etc and replaced the rubber lines where appropriate and fuel filter. Still have the problem so will change the fuel pump and gas cap. Gonna figure it out one way or another. jim