i heard stock fuel lines are adequate up to 300hp. but what about the other sizes starting with -6AN up to -10AN. The reason i am asking is because i am building a motor thats going to be around 450 500hp will -6AN be enough or should i go with -8AN. this motor is also carberated

 

<--stock fuel lines and I am running 397 rwhp on a blower.

 

AN lines are measured in 16th's of an inch -8an= 8/16's=1/2 inch. I make it a rule of thumb that once the HP passes the 500hp mark 1/2inch or -8an line just to make sure the volume is fuel is good. On some Mustangs the stock fuel line is only 5/16 and thats a push for 300hp on a Carbed engine. If I were you I would go -8an (1/2 inch) just to leave you some room to grow although -6an line (3/8) would probably do fine.