To compensate for the thermal expansion of the valve, a gap is set between the end of the valve stem and the camshaft cam
With an increased clearance, the valve will not open fully, and with a reduced clearance, it will not close completely
The gap is measured with a feeler gauge on a cold engine (at a temperature of +20º C) between the camshaft cam (the cam must be directed upwards from the tappet) and the valve tappet
The nominal gap for the intake valve is 0.17-0.23 mm, and for the exhaust valve 0.31-0.37 mm
The gaps are adjusted by selecting the thickness of the pushers
Spare parts are supplied with sets of pushers of different thicknesses
Regarding the timing drive, the valves located on the right are exhaust, on the left are intake
The work on adjusting the clearances in the valve drive is the same for all engines
Preparing the car for the task
We set the piston of the first cylinder to the TDC position of the compression stroke, as described in the article "How to set the TDC of the first cylinder of the Mazda 6 engine"
Unscrew all the spark plugs
Remove the cylinder head cover, as indicated in the article "replacing cylinder head gaskets"
We measure the gaps between the cams of both camshafts and the valve lifters of the first cylinder with a feeler gauge
Write down the measured clearances
We turn the crankshaft by the pulley mounting bolt 180º each time, measure and record the valve clearances of the remaining cylinders
Cylinder order 1-3-4-2
It is necessary to replace the tappets of those valves, the gaps in the drive of which differ from the nominal values
After measuring all the gaps, set the piston of the first cylinder to the TDC of the compression stroke
Remove the camshafts
We remove the valve tappet from the cylinder head socket, which requires clearance adjustment, and record its thickness (it is indicated on the inner surface of the tappet)
The number printed on the inner surface of the valve lifter is the tappet thickness
Only three digits after the decimal point are applied (for example, the number "650" means the thickness of the pusher is 3.650 mm)
We calculate the thickness "H" of the new pusher using the formula (all values in mm)
H = B + A - C, where A is the measured clearance; B - the thickness of the old pusher; С - nominal gap
Install the new pusher in place
In the same way, we replace the tappets of all valves that require clearance adjustment
We are installing the camshafts, but we are not installing the timing gear yet
Turn the crankshaft 90º counterclockwise so that all pistons are in the middle position
Scrolling the camshafts for the hexagons made on them, we measure the gaps obtained with a feeler
If the gaps differ from the nominal values, repeat the adjustment
If all the clearances correspond to the nominal values, install the timing gear and all removed parts in the reverse order