Is it easy to adjust valves while i have the cover off as well? Whats the correct valve adjustment procedure?
I dread doing valve adjustments, but that's probably just because it's so repetative (four valves per cylinder does have a down side).
You want to do this adjustment on a dead-cold engine. The free-play in the valves is there to account for thermal expansion of the various metal parts, so it's important that the engine is at room temperature.
Once the valve cover and upper timing belt covers are off, you will need a 17mm socket, extension (3" will do) and ratchet for turning the crank, a 10mm box-end wrench for the tappet nuts, a flat-head screwdriver for the tappets themselves and two feeler gauges: 0.007-0.009" for the intake valves and 0.009-0.011" for the exhaust.
Start by turning the crank until cylinder No. 1 is at TDC (top dead center) of it's compression stroke. You can tell by looking at the cam gear and the crank pulley: The "UP" marking on the face of the cam gear will be up and the two grooves will align with the valve cover mating surface. You should be able to sight down the pointers on the lower timing belt cover at the crank pulley and see the single TDC groove (in the rim of the pulley) line up. There should also be a group of 3 grooves on the crank pulley for ignition timing... The TDC groove should be to the right of those.
All four valve rockers on cylinder No. 1 (closest to the timing belt) should be slightly loose at this point. Break loose all four tappet lock-nuts (the nut on each rocker arm) and back out the tappets (the screw in the center of each locknut) a turn or so. Don't try to do more than one valve at a time... The idea to be precise, not flat-rate it. Slip the appropriate feeler gauge between the bottom of the tappet and end of the valve stem (the metal pin in the center of each spring). Put your box-end wrench on the lock-nut and use the screwdriver to tighten the tappet.
The goal here is to get the clearance between the tappet and valve stem to the exact thickness of the feeler gauge. If you over-tighten the tappet, you will start to compress the spring and open the valve you're working on, causing the clearance to be too small once you remove the feeler and the valve closes again. If you don't tighten it enough, the oil film between the cam, rocker, tappet, feeler gauge and valve stem may result in too large a clearance. Too big a clearance will result in a noisy valve train where as too small could result in a burnt valve... As such, it's better to be a little loose. It may help you get a feel for what's going on if you tighten the tappet until the valve starts to open, back it off till it's loose and repeat a few times. Some people say to do it by how much drag you get when you try to move the feeler gauge around, but I've found the exact angle you hold the gauge at can affect that quite a bit.
Anyway, once you have the tappet where you want it, hold the screwdriver (and thus the tappet) perfectly still while tightening the locknut with the open-end wrench you put in place earlier.
Repeat with the other 3 valves on this cylinder, making sure you've got the proper feeler gauge for the valve you're working on.
Rotate the crank 180° counter clock-wise... The cam pulley should rotate 90°. Repeat the above on cylinder No. 3. Rotate another 180° (TDC on the crank, the cam pulley will now be upside down) and adjust cylinder No. 4 (closest to the distributor). Rotate still another 180° and adjust cylinder No. 2. In order, that's 1, 3, 4, 2 - the engine's sparkplug firing order. If this is your first valve adjustment, it's probably not a bad idea to go through another cycle checking your work with the feeler gauge.