Originally Posted by Accord_Man
Whats the advantage of an engine with two cams when comparing it to a single cam engine with the same number of valves and the same displacement, and the same compression ratio. Thanks.
Generally they breath better and rev higher.
DOHC generally have multiple itake and exhaust valves/pot, but of course there are three valve heads and even two valve (slack engineers and accountants). For a two valve there is less deflection of the camshaft and better angles of attack through canting and pent roof designs.
Tackling four valve and higher:
There is are a myriad of advantages, but consider you have two valves doing the job of one. This reduces the displacement (acceleration) of the valve and mass. Both these factors are major considerations when looking at force (f=ma).
The valve is less likely to flex or bounce so the rpm redline is typically higher, thus increasing your top end power capability. The radius of the valve is smaller so less likely to deform and more likely to seat when under duress.
The valve train losses are less because of f=ma. Flanking and ramps of the cam lobes is more moderate. Spring tensions are less also, unloading the camshaft and resulting in less shaft deflection and wear. Point load is more evenly spread.
The head itself has a reduced localised stress, both through reduced valve train stresses and stress distribution via two camshafts instead of one. The mass of the individual camshaft is less, reducing rotating mass.