Is 8 AN line to the fuel pump than 6 AN line from pump to carb ok to run on a 509 NA motor?

I run 10an from tank to aeromotive pumps, then 8 to engine then 6 is my return line size, if the motor puts out 500hp or more and you turn 5200 rpms or more i would use 8 throughout

-8 will surely work but I believe your -8 and -6 combination will also work. The way to be safe is to run at least a temp fuel pressure gauge near the carb to make sure you can hold 6+ lbs at WOT.

thanks guys. I'm running a mechanical pump so its set @ 7 I believe, but I will put a gauge on at the rail and check pressure at WOT.

one more question, can I run my burst line back to my fuel/water seperator? It has 4 ports and it's only 10" from my pump, would make a clean and easy install if possible.

A good fuel system is not just a matter of what size lines you use. Your engines requirements will dictate what your fuel system must be. There is no such thing as too much fuel supply. Pressure must be regulated, but let the supply flow as much as possible. When building a fuel system, start at the tank. Make sure the pick up tube is not the size of a straw. Get a good set of pumps, avoid using any 90* pipe fittings, use only 90* smooth bend AN fittings. High flow filters, and a return regulator are a great addition. While -8 AN will probably do, -10 AN lines will only help.