Rocker shaft assembly 320/03931 JCB Dieselmax, aftermarket

For the JCB Dieselmax 444 engine: rocker shaft assembly 320/03931, an aftermarket part.

The rocker gear is lubricated through a passage in the shaft; neglected oil changes quickly wear the bushes. Spring type and arm count depend on the engine, so the assembly is chosen by part number. When replacing it, check the valve bridges and pushrod ends too. The shaft bolts to pedestals on the cylinder head; springs between the arms keep them in place along the shaft. Each rocker arm has an adjusting screw and locknut for setting the valve clearance. When an arm bush wears, the arm rocks on the shaft and presses on the valve bridge at an angle. The shaft is hollow and serves as an oil gallery.

Specifications

Compatibility

The part is listed for JCB 3CX and 4CX backhoe loaders. The assembly is the hard-spring version, with eight rocker arms on the shaft. The catalogue also has the genuine version of this part. Other parts are in JCB Dieselmax engine.

Fitting

Place the assembly on the head and tighten the pedestal bolts from the centre outwards in stages, making sure the pushrods seat in the arms. Then set all valve clearances to JCB figures. Remove the old assembly in one piece together with its pedestals.