| Re: Timing adjustment
I'm not sure whether the procedure varies from standard heads to vortec heads but the procedure for both ignition timing and valve lash adjustment for standard heads goes as follows.
For ignition timing you need will need a timing light. You hook the timing light up to the #1 spark plug and point the light at the little metal tab that is notched near the crank pulley. You start the car and point the light at the tab and the light should flash as the notch on the harmonic balancer passes past the timing tab, where the light spots the notch passing the tab indicates the timing set. For my engine the timing is 0 degrees BTDC. Most engines perform a little bit better with a bit of advance, this is done by unbolting the hold down bolts of the distributor and rotating it until the desired timing is reached.
For valve lash adjustment you need to have each cylinder valve you're working on (intake, exhaust) at TDC for this adjustment. Now unthread the rocker arm nut completely, make sure it's completely separating the rocker arm from the pushrod. Now rethread the nut back on and simultaneously twist the push rod, keep doing this as you thread the nut down, once you feel the slightest tension on the pushrod as you twist it stop. Torque the nut down 1/2-3/4's of a turn more, most people stick with 3/4's of a turn, the valve lash is now set for this valve. Proceed to the next valve. | 
