Fuel delivery issue...Help!

[cb66valiant]

So, i got a 66 Valiant, 340, 750 Holley, 5/16 fuel line, mechanical fuel pump. I have had some fuel delivery issues at highway speeds. Thought I had figured it out. But when I was at the Nats last month, i shifted into high gear through the 1/8 mile, all is well, it then, at about 5000 rpm, started to cut out, i lifted at the 1000 ft mark (Mostly because i had to drive it home 100 miles). Still ran a 14.48 but only 82 mph. It ran 9.20 @ 79 mph in the 1/8. It did not act up on the highway on the trip back. So I cant believe i would need an electric fuel pump or larger fuel line. When stock 340's ran the same setup. My friend ran a 72 Cuda with a 340 that ran 11.80's on 5/16 line.
Can anyone help me out. I would really appreciate it.

Thanks,
CB66

P.S.- Photo is from local track.

 

[1wild&crazyguy]

check the rubber fuel hose at the sender for cracks.

I run a stock fuel pump on my 340 4spd '67 valiant-13.80's -104mph with lots of tire spin.

It's not cause you need a bigger/better pump.

check float level, plugs for mixture=jetting, and connection/hoses.

maybe the pump is taking a sht too, but check the other stuff as well.

 

[cb66valiant]

Thanks 1wild,
Brand new pump the day I left for the Nats. The hose at sending unit had collapsed on me a couple months ago, so i changed that. Brand new carb haven't given that any thought. Might have to check it out.