Stop the engine and remove the air filter housing. Mark all hoses and connectors that are disconnected from the air filter housing.
Remove the tips with high-voltage wires from the spark plugs and take them away from the cylinder head cover.
Remove the PCV valve and high voltage wire bracket from the cylinder head cover. Fasten the accelerator cable to the side with a piece of wire.
Clean the spark plugs with compressed air to prevent dirt from entering the engine cylinder after the spark plug is removed. Remove spark plugs.
On the high-voltage wire of the spark plug of the first cylinder, fix its position on the ignition distributor housing with a number «1». Do the same for other cylinders (numbers «2», «3», «4»), then remove the cover and disconnect the wires from the ignition distributor.
Remove the cylinder head cover.
Turning the engine crankshaft in the direction of its working rotation for the pulley mounting bolt, set the piston of the first cylinder to TDC in the compression stroke, while the rotor of the ignition distributor must be aligned with the mark «1» on the distributor housing. Otherwise turn the crankshaft clockwise one full turn. Use a feeler gauge to measure the exhaust valve clearance on cylinders 1 and 3 and the intake valve clearance on cylinders 1 and 2.
Record the measurement results.
Rotate the crankshaft one turn (4th cylinder piston at TDC on the compression stroke) and measure the clearances on the remaining valves.
Record the measurement results.
If the valve clearances are not as specified, adjust them.
Rotate the engine until the lobes of the camshaft above the valve requiring adjustment are pointing upwards.
Loosen the lock nut and carefully turn the set screw in or out until the feeler gauge slides in with little effort. Use a screwdriver to fix the position of the set screw and tighten the lock nut. Recheck the clearance.
Pic. 2.23. Cylinder head bolt tightening sequence
With the cylinder head cover removed and the engine warmed up, use a torque wrench to check the tightening torques of the head bolts. Loosen one bolt by turning it a quarter of a turn, then tighten to the torque given in the manual. Repeat this procedure for all cylinder head bolts in the sequence shown in fig. 2.23.
Install the cylinder head cover with a new gasket and tighten the bolts evenly to the torques given at the beginning of the section.
Screw in the spark plugs, install the ignition distributor cap and connect the high voltage wires. Install the air filter, connect the hoses, connectors and vacuum hoses.
Start the engine and check for oil leaks between the block head cover and block head.