When the timing mark on the damper is aligned with the O degree mark on the timing gauge (attached to the front cover), the number one cylinder is at TDC of the compression stroke, right? At that point, the number 1 spark plug should be firing (without retard), right?

Yes and no. The damper will allign with the 0 mark twice for each time the piston moves up. Once during compression and once during exhaust. Now for timing, If we wait till the piston is at "0" true top dead center then the explosion will happen too late and you will loose power. If you take a look at the #1 cylinder valves you will have see the intake valve open and close at that point continue to turn the engine till you hit TDC. that then becomes the spark for number one.

When the timing mark on the damper is aligned with the O degree mark on the timing gauge (attached to the front cover), the number one cylinder is at TDC of the compression stroke, right? At that point, the number 1 spark plug should be firing (without retard), right?It could be #1 or #6:thumbsup: