3/8 vs 5/16 fuel lines

sorewrist1 said
I'm running a 360 with a purple cam ported heads RPM intake thermoquad carb. It has a electric and mechanical fuel pump. I'm still running the 5/16 fuel line. When I floor it it pulls great till 3000 and won't rev much higher. Another time I was crusing about 2500 floored it and it pulled great to 5500 that's it. Now stock 5/16 from the sending unit to the electric fuel pump with fittings to the mechanical pump with fittings to the pressure regulator with fittings to fuel filter to the carb. Also have a fuel filter before the electric fuel pump and both are new. So it's a small fuel line and a lot of fittings Does this sound like a fuel restriction problem? Oh the carb was rebuilt by Rusty Rat Rod and he did a great job No bog and love the sound of those secondaries Thants. Jim

I’d check the fuel filler cap to make sure it’s venting and/or ensure any tank vents are not plugged. Bypass the mechanical pump and see what happens, and vice-versa. But if you start throwing parts at it I’d start with a fuel pressure gauge to know what pressures you have and you might be able to identify the issue. Buy a fuel pressure tester, or a gauge and a few feet of fuel hose, route it up between the hood and cowl or fender, wrap a cloth around the gauge, use some tape/zip ties to keep it positioned so you or a passenger can read it and go out and drive. It’s a temporary connection for testing. You gotta improvise a setup to see what’s what.