Series 60 Overhead Adjustment

This week our Thursday class was cancelled due to Thanksgiving, so with permission from my instructor I have used Tuesday's class for my weekly blog assignment.

Tuesday's class is Diesel Engine Service and Maintenance, where we have learned the basic operating principles of a diesel engine, as well as service procedures.

This week we did injector and valve adjustments. The procedure is simple, first the engine is barred over until one of the cylinders is on valve overlap. Once we have a cylinder on valve overlap, we refer to our service information to determine which cylinders require which adjustments. On our Series 60 engine, injector height and valve lash are adjusted on different cylinders.

A special injector height tool is used and inserted in a small hole in the injector hold-down clamp. The height tool is of a specified height (ours is 81mm). Once the tool is in place, a flat on the tool is swiped across the top of the injector plunger until it produces a slight drag and wipes the oil off the top. The injector height is adjusted by loosening the locking nut and turning the adjusting screw with an allen head wrench.

Valve lash is adjusted the same way, however the measurement we are taking is with feeler gauges between the valve stem and valve button at the end of the rocker arm. Our goal is to fit the specified feeler gauge (.008" for intake valves, .026" for exhaust valves) in there and produce a smooth, even pull. Too much drag and the valve must be loosened, too little and it must be tightened.

We proceed in this manner until the valves and injectors have been adjusted on all cylinders.

Access is easier with the Jakes off, even though service information recommends leaving them on.

The height gauge for measuring injector height. Note the locating hole in the hold-down clamp, and the flat at the top of the gauge which is swiped across the top of the injector plunger.

My reflection:

Once again we get back to a word every mechanic and technician should be familiar with: accessibility. While it tends to be better on the big trucks than it is on cars, we still encounter plenty of accessibility problems on the rigs too. For instance, according to our service information, these adjustments should be made without removing the Jake brakes (if possible). Removal of the Jake brakes was necessary to gain any reasonable access to the valves and injectors.

Another accessibility issue was injector height adjustment on cylinder #6. Because it is somewhat recessed behind cab parts and closer to the firewall, it was necessary to actually lay on top of the engine to see what we were doing with the height injector tool (as it must be set inside the locating hole on the hold-down clamp to get an accurate measurement).

The same scenario would be encountered if we were to follow procedures to drain the cylinder head of fuel for injector removal, which requires disconnecting the fuel fittings at the very back of the head.