So- there have been a few threads recently about upgrading CAMs and/or advancing the ones that are there. The mechanics of how these upgrades work is/was beyond me, so I went to "how stuff works" and reviewed their explanation of Camshafts. Here's the link: http://auto.howstuffworks.com/camshaft.htm

I found it quite helpful, but still have a couple questions.

1)- I understand that having the intake valve open longer (past the bottom on the intake stroke) at higher rmps is good because more fuel can enter the cylinder- but it seems like even 1200 rpm idol would be worth the extra fuel. So- what is the down side of a performance cam that has valves open longer? Higher fuel consumption?

2)- How does advancing the cam increase performance? It seems that you are opening the exhaust valve longer, but the intake valve wouldn't open until after the intake stroke had started. I think this is just a gap in my understanding of how the thing works.

Thanks for your insight.

(p.s. - there is an interesting explanation of the Ferrari variable cam system on the last page of that howstuffworks sequence)