orh, i said a retard is someone slow in brain development touch
a sensitive spot ah? if u not one den so angry for feck? 
ever heard of hydraulic cam gears? those are the gismos that
give the cam their advance and retard while the engine is moving.
and u of course will have no idea wad i'm toking about lah! u are
an engine idiot wad!
the one with broken english wanna correct mine ah? go buy some
paper and sticks make a kite lah. i heard marina south very popular
so? i flamed u for doing something LPPL like expanding the
meaning of dual vvt-i. does that mean i do not know the difference?
grammer poor, comprehension muz be better lah. go outside become
laughing stock u know?
in case u haven't noticed, my explanation is above the last para
u qouted. didn't u go to school? if not how come u cannot tell the
diff between a thesis and an explanation? btw, i dun like to shoot
junior members. i like to shoot ignorant members 
but u still haven't explained wad happens to the cams
MECHANICALLY as they are advanced or retarded! keep saying advance
to enable earlier intake and when retarded, the valves dun open as
early for feck? if u know how to advance or retard a cam in the
first place, why keep avoiding the explanation by using such vague
and generic explanations?
lets end this once and for all. juz answer this question:
is it true that u advance a cam by turning it forward and retard it
by turning it in the reverse direction or not?
simple yes no answer will do.
hello. earth to mars. since when did i said "simply by changing
the speed of rotation of the cams like u said"? u dunno how to
argue properly nevermind. mai anyhow misqoute me lor.
wad u have juz said confirms that not only do u know nuts bout DOHC
engines. u know nuts bout SOHC engines . dun u know that the amount
of overlap in a SOHC engine is invariable? the amount of over lap
is dictated by the amount of duration the inlet cams crosses over
to the duration of the exhaust cams. and since both inlet and
exhaust lobes are FIXED along a SINGLE cam in a SOHC engine, they
cannot be advanced or retarded to affect overlap. the entire cam
can only be advanced or retarded along with the whole intake and
exhaust timing. if u have been reading, u would realize that this
is one of the primary advantages of DOHC which can have either the
exhaust cam or the intake cam advance or retard itself to acheive
diff amount of overlap.
this is by far ur best explanation of how overlap works. if only
i can say the same for the rest 
