Both inlet and exhaust valve head diameters are 1/8 inch smaller with a corresponding decrease in valve seat diameters. Sodium cooled exhaust valves are no longer used.

The smaller valves are recessed another .050 inches into the head, further minimizing the possibility of valve malfunction and exhaust valve interference with the piston.

New cast-in passages in the cylinder head provide this engine with full circle spark plug cooling.

The thermostat by-pass cooling system, described in detail earlier, has also been adapted for use with the 348 cubic inch engine.

Distribution caps with copper, instead of aluminum, inserts and stainless steel distributor point springs, improved ignition system performance.

Electrical

PASSENGER CAR

The battery charging circuit is now separate from the generator-to-load circuit. The two individual circuits are both taken off the voltage and current regulator.

In this simplified system the line from the hot terminal of the starter to the load is eliminated.

Exceptions to this system are found in cars having power-operated windows, seats, or convertible tops. Circuits for these power assists continue to be connected to the hot terminal of the starter.

The ignition ballast resistor previously mounted on the dash is eliminated for 1959. In its place, an equivalent amount of resistance is built into the ignition circuit of the starting motor harness. It takes 5 feet of special high resistance wire to accomplish this purpose.

CAUTION: Do not attempt to replace the special wiring with regular copper wire.

The 348 engine with the 3x2 carburetor and special camshaft option still uses a special ballast resistor, and has no resistance wire in the harness.

Wiring at the ignition switch is simplified by use of a single 4-way connector.

Location of the battery is similar to 1958 except that it is higher and turned 90°, with the positive post on the outboard side and the negative post on the inboard side.

Battery identification is provided by the last three digits of the part number which are stamped into the top of the battery case.

To further assist identification, the top of the negative post of the 61 Amp. Hr. Battery is colored green. The 11-Plate 70 Amp. Hr. Battery is approximately 3/4" taller than the 53 and 61 Amp. Hr. batteries and thus easy to identify.

The specified torque on the new type battery hold down is 12-18 foot pounds. This torque should not be exceeded. It is normal to have about 1/8" space between the hold down bar and the radiator tie bar.

A new battery testing procedure has been developed that is easier and more accurate than those used in the past.

Starting Motors

Series wound starting motors are used on all except 348 cu. in. engines, 348 cu. in. engines use a (more powerful) compound type starting motor.

When replacing a starter motor the more powerful compound motor must always be used on the 348 cubic inch engines.

The compound motor and the series motor have the same external dimensions therefore, always refer to the part numbers stamped on the field frame.

Turn Signals

The turn signal switch has been divorced from the canceling mechanism, with the switch now mounted on the lower end of the mast jacket (Fig. 9).

A bowden cable is used to actuate the switch. Adjustment is accomplished automatically by operating the turn signal lever through one complete cycle. The new switch location eliminates the routing of six turn signal wires through the mast jacket.

The canceling cam on the steering wheel has been redesigned to provide a much smaller canceling angle, so as to insure cancellation even on gentle turns.

Due to the fact that two stop light bulbs instead of one flash when making a turn, it was necessary to use a new flasher to handle the additional bulb load. The new flashers cannot be used interchangeably with past models.

Brake Alarm

A parking brake alarm with a flashing light is standard equipment on Impala (and Nomad) models and an accessory on all other models. The flashing device is incorporated in the special number 257 bulb.

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