The idea of setting the valves is to adjust the size of a specific gap that has been built into the engine's design to allow for variation in the expension rates of different parts as the engine heats up. (Pictures of the gap to come shortly). This is the gap at the end of the rocker arm. You need to adjust the gaps between the rocker arms and the valves for each cylinder in the order 1,2,3 and 4 see engine orientation for cylinder order.
So how do you adjust the valves for each cylinder in turn according to the order above?
You need to turn the engine backwards to the top dead center point for the cylinder that you are adjusting (i.e. cylinder 1 first etc.). The engine turns 180 degres clockwise between top dead center on each cylinder in the order that it fires which is backwards (i.e 1,4,3,2) So to go from top dead center on cylinder 1 to top dead center on cylinder 2, we need to turn the engine 180 degres anti-clockwise. Always based from you looking from behind the car. Top dead center for number 1 and for 3 will be marked by a notch by itself on the pulley. (picture to follow). There will probably not be a mark on the 180 degres opposite for top dead center for 2 and 4. If you don't have a mark for 2 and 4, then you need to make one. You need to find the opposite 180 degres from the mark the factory put on the pulley
Remove the distributor cap.
Find top dead centre for cylinder 1. This will be where the notch for 1 & 3 is aligned to the split in the engine case and the rotor arm in the distrubutor points to where the lead for number one spark plug is.
Take off the rocker cover for the 1 & 2 cylinders - the right hand one. You'll probably need to use a couple of big screwdrivers to wiggle to clip off.
You've now exposed the rockers. The pushrods push the bottom end of the rockers, the valves are at the top end. At the top end of the rockers there is a gap between the valves and the rockers that you will hopefully be able to slide a feeler gauge through. At the bottom of the rockers there is a patterned grip that you can push against with your thumb to ensure there is no slack before making the adjustment.
You need to adjust both the intake and exhast valves for the cyliner.
Normally you'd do the intake (the inner valves) before doing the exhaust (the outer valves).
Push the bottom of the rockers to take up any slack. Get your 0.15mm feeler gauge and slide it between the rocker arm and the valve spring. It should slide in with some resistance - you shouldn't need to force it, and it shouldn't be loose. If the gap is not right, then you need to get your 13mm (?) spanner and your flat blade screwdriver out. Loosen the lock nut on the rocker arm and turn the adjustment screw in out out until the gap feels right. Tighten up the lock nut and then test again with the feeler gauge - if it's not right, do it again.
Then repeat for the other valve.
To move on to the next cylinder to adjust, you need to rotate the engine enti-clockwise 180 degrees.