Details details details, Hmm...I wanna know Options

[JonMarkos]

While reading through ice's post on his 5s-gte build, and a few other engine rebuild post I see people making comments about cam duration and lift. Some people recommended a duration of 268 and others said 272 degrees. I don't remember if any said at what lift though. My question is...How do you know that a 272 duration would work best in 5s-gte setup? Is there a mathematical formula you used, or some equation you applied calculating in the other aspects of the engine? Or is this stuff that is just repeated from other people out there that have done the build...and if so...how did they figure it? I have a pretty good mechanical knowledge of how a vehicle's engine works, and what makes the car go forward when you tell it to, but when it comes down to details like this it's all Greek to me...any help?