larry-
short answer, no. #14 is designed to carry 15 amps @ 120v. #8 is designed for 50 amps?? ish at 120v. so in theory, two #14's could move 30 amps at 120v.
code doesn't allow doubling, or tripling up conductors to allow for higher current, however it does work, and i do this sort of thing on my off-grid system.
electricity takes the path of least resistance, and resistance gets higher as wire warms up. so lets say you had two wires carrying the same load. lets say one had a slightly better connection, thus less resistance, it would begin to carry more load, until it started to get warm, and the load would shift slightly to the other wire... in other words, things sort themselves out naturally in this scenario.
charts are out there showing the area in mm squared or inches squared or whatever. this is the key number. i always size the multiple conductors to the same amount of area squared as the conductor i should be using.
hope this helps.
adam