A special high performance camshaft is used in combination with mechanical lifters. The recommended valve lash (hot) is .012 on the inlet and .018 on the exhaust.

The engine has a heavy duty generator. Connecting rod and main bearings are 348 truck engine bearings. Spark plug wires are copper core and a special heavy duty starting motor is used. The ignition coil and ballast resistor are the same as currently used on the high performance Corvette.

TRUCK

Six Cylinder Engines

A number of refinements have been made to the 261 cubic inch engine to improve valve train durability. New valve springs, which provide an approximate 10 percent reduction in stress, are used in the Jobmaster engine. Aluminumized inlet valves minimize the formation of deposits on the valve face, resulting in better seating and longer lasting valves.

A new heavy-duty piston, which features a thicker dome, a heavier skirt, and a cast-in steel insert in the top side of the upper compression ring groove, are used in the Jobmaster six.

A full-flow oil filter, in place of the partial flow, by-pass type previously used, has been provided as regular equipment.

The new by-pass thermostat incorporates a primary and secondary valve (Fig.8). During the warm-up period, or until sufficient temperature is developed to open the primary valve, the radiator is by-passed, as all of the coolant is diverted through the secondary valve ports of the thermostat and through a by-pass horse back to the water pump to be recirculated through the engine.

Fig. 8 - By Pass Type Thermostat

On units equipped with automatic transmission and oil coolers, the by-pass hose i connected to the lower radiator tank instead of the water pump.

This by-pass cooling system is used on all heavy-duty truck engines.

A 160° thermostat will be used on all 1959 trucks except model 10802 school bus, which uses a 151° thermostat.

V-8 ENGINES

283 Cubic Inch Engine

The Taskmaster and Super Taskmaster (283 cu. in.) engine incorporate a new heavy-duty full skirt piston.

Lack of ventilation in the distributor cap of vacuum spinner governor equipped engines, has resulted in the corrosion and failure of distributor point springs. To remedy this condition a new stainless steel distributor point spring is used.

In other change affecting the distributor, a distributor cap incorporating copper, instead of aluminum, inserts is used for all Taskmaster and Super Taskmaster engines.

The new thermostatic by-pass cooling system, described in detail earlier, has also been adapted to all 283 cubic inch V-8 engines.

322 Cubic Inch Engine

The Loadmaster engine is again used exclusively in the 10802 school bus model. This engine is identical to the assembly offered in 1958.

348 Cubic Inch Engine

The two barrel carburetor, 348 cubic inch engine, released as a 1958 mid-season change, is available as an option on the 70 and 80 series trucks, except school bus. This engine is identical to that released for the 90 and 100 series except for the carburetion.

The Workmaster, a four barrel carburetor version of the 348 cubic inch engine, is standard on the 90 and 100 series, except for the school bus model. This engine is not available as an option on the 70 and 80 series trucks.

The 348 cubic inch engine is essentially the same as that offered in 1958, except for the following changes:

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