The adjustment procedure for intake and exhaust valves is essentially the same for all Civic engines as they share a common design, whether 2, 3 or 4-valve-per-cylinder. All engines employ overhead cam(s), overhead valve designs that adjust by a screw and locknut method. Therefore, the procedures in this section will cover all Civic series models. Just be certain to follow torque specifications for your particular model.
As part of every major tune-up or service interval, the valve clearance should be checked and adjusted if necessary.
If the valve clearance is too large, part of the lift of the camshaft will be used up in removing the excessive clearance, thus the valves will not be opened far enough. This condition makes the valve train noisy as they take up the excessive clearance, and the engine will perform poorly, since a smaller amount of air/fuel mixture will be admitted to the cylinders. The exhaust valves will not open far enough to vent the cylinder completely; retained pressure (back pressure) will restrict the entry of the next air/fuel charge.
If the valve clearance is too small, the intake and exhaust valves will not fully seat on the cylinder head when they close. This causes internal cylinder leakage and prevents the hot valve from transferring some heat to the head and cooling off. Therefore, the engine will run poorly (due to gases escaping from the combustion chamber), and the valves will overheat and warp (since they cannot transfer heat unless they are firmly touching the seat in the cylinder head).
While all valve adjustments must be as accurate as possible, it is better to have the valve adjustment slightly loose than slightly tight, as burnt valves may result from overly tight adjustments.