The need to adjust the clearances in the valve drive is evidenced by a distinct loud knock heard when the engine is idling from the driver's seat with the hood closed
Increased clearances do not lead to emergency engine breakdowns, but cause increased wear of the valve train parts.
In addition, with increased intake valve clearances, the filling of the cylinders with the combustible mixture worsens and, as a result, the engine power decreases.
With the complete absence of clearances at the exhaust valves, in addition to uneven operation and a decrease in engine power due to a decrease in compression in the cylinders, it is possible for the valve plates and their seats to burn due to overheating, since the valve that does not fit tightly into the seat is poorly cooled.
The gap should be measured on a cold engine, at a temperature of + 20˚C, between the tappet and the tip of the adjusting bolt with the valves fully closed.
The nominal clearance for inlet valves is 0.25 mm, for exhaust valves 0.51 mm.
The two-arm tappet acts simultaneously on two inlet or outlet valves.
We prepare the car for the job.
Remove the cylinder head cover.
We install the piston of the first cylinder at the TDC of the compression stroke (article - Installing the TDC of the first cylinder Cummins ISF2.8).
In this position, all four valves of the first cylinder will be closed and the gaps between the pusher stops and the tips of the adjusting bolts will be maximum.
Cylinders are reported from the crankshaft pulley.
To set the piston of the 1st cylinder to the TDC position of the compression stroke, it is necessary to remove the master disk of the phase sensor installed at the rear end of the camshaft (to gain access to the groove on the rear end of the camshaft), and this cannot be done on the engine installed on the car.
With an accuracy sufficient to adjust the valve train clearances, the camshaft can be positioned visually.
The camshaft must be turned so that the rollers of the rocker arms of the drive of all four valves of the cylinder, which is being adjusted, rest on the back of the camshaft cams, and the rocker arms can be moved by swinging within the gap.
We loosen the tightening of the locknut of the adjusting bolt of one of the rocker arms, keeping the bolt from turning with the second wrench.
We insert the dipstick into the gap between the pusher stop and the tip of the adjusting bolt.
Keeping the lock nut from turning, turn the adjusting bolt clockwise until the probe in the gap can be moved with light effort.
While holding the adjusting bolt from turning, tighten the lock nut and check the clearance.
Repeat the adjustment if necessary.
Adjust the clearance for the second pair of valves in the same way.
Turn the crankshaft exactly half a turn.
With this position of the crankshaft, all four valves of the 3rd cylinder are completely closed and their rocker arms are released.
Adjust the clearances between the pusher stops and the tips of the adjusting bolts of the 3rd cylinder.
By subsequent turns of the crankshaft exactly half a turn, set the pistons of the 4th and then the 2nd cylinder to TDC of the compression stroke and adjust the clearances for the remaining valves.
Install the cylinder head cover and all removed parts in the reverse order of removal.
Replace the heavily crimped bonnet gasket if necessary.
Ps. With the engine installed on the car, the valves can be adjusted without removing the engine.
To do this, remove the cylinder head cover.
We insert a thin pin through the hole under the nozzle and, slowly turning the crankshaft, determine the top dead center in the cylinder.
The camshaft must be turned so that the rollers of the rocker arms of the drive of all four valves of the cylinder, which is being adjusted, rest on the back of the camshaft cams, and the rocker arms can be moved by swinging within the gap.
In this position, we check and adjust the clearances.
