question about oversize valves?

[400man]

ive got a question about oversized valves.......what exactly is different from stock valves? I know there are "+1mm" and such, is the valve area bigger or is the valve longer so it opens more or what?

[Longdong]

The vavle circumference is bigger.

[400man]

ok thats kinda what I was thinking. do you have to have machine work on the head to be able to use bigger valves?

[Longdong]

Yes

[JOHNDOE83]

Its a nice lil power upgrade also.