I ran outta space in the other post...
You have to remember that the valves do most of their movement in the way of
open/close during one of the engine cycle
strokes. Also, both the intake and exhaust valves operate during one complete 360 degree revolution of the engine or 2 of the strokes, back to back. During the other revolution they are essentially closed but the camshaft is in different positions....
...so, you
don't want to adjust the valves in the TDC position that is in the narrow time between the Exhaust and Intake strokes...
If you look at the actual start of the cycle, it begins with the intake stroke. Keep in mind, that I mention the clock position because that is your reference point with the wrench...
...the
Intake Stroke starts at
TDC at 3:00, the piston moves downward, the intake valves
open, a huge gulp of fuel and air rushes in, the valves
close before
BDC at 9:00 and...
...the
Compression Stroke starts at
BDC at 9:00, the piston is hurled up, squeezing the fuel and air to 1/8th it's original volume, the spark plug fires just before
TDC at 3:00, there is a tremendous earth shaking explosion and...
...the
Power Stroke starts at at
TDC at 3:00, the piston screams downward under tremendous heat and pressure to
BDC at 9:00, a simply incredible amount of torque is unleashed and...
...and
Exhaust Stroke starts at
BDC at 9:00, the piston slingshots upwards, the exhaust valves
open, all the burned gas, oil, dead bugs, and smoke is forced out, a loud
THUMP resonates everywhere, the valves
close before
TDC at 3:00 and...
...
if everything is still in one piece, the cycle repeats again