These plugs still require gaskets and can not be interchanged with standard reach plugs.

The new vacuum take-off at the intake manifold for distributor vacuum advance on V-8 models makes it necessary to disconnect the vacuum advance hose when checking timing on these engines.

Engine

PASSENGER CAR

Six Cylinder Engine

While 6-cylinder engine displacement remains at 235 cubic inches, modifications produce significantly better fuel economy than in 1958.

A new camshaft and new valve lifters provide the principal means for effecting the rise in fuel economy. The decreased valve lift and a smaller amount of valve overlap not only produces a fuel savings, but at the lower and intermediate speeds results in even higher torque than that delivered by the 1958 Six-cylinder engine. The toque increase within this broad speed range materially improves vehicle performance.

New hydraulic lifters have the spring removed from the ball check valve and the cage has been revised to reduce ball travel.

Use of lighter valve springs and improved lubrication in the valve rocker section increases valve train durability.

By removing the 1/15" orifice from the rocker shaft oil delivery passage in the cylinder block and closing off the rocker shaft oil connector tube spill, the possibility of clogging in the oil delivery circuit has been minimized and the rocker shaft now receives full-pressure lubrication.

The lowered hood line necessitated redesign of the intake manifold, valve rocker cover and engine water outlet casting.

283 V-8 Engines

A molded rubber rear main bearing seal replaces the asbestos-jute type formerly used. Seal replacement is greatly facilitated because the crankshaft does not have to be removed for insertion of the upper half.

Tops of the inlet valve guides are machined and incorporate a new valve stem seal designed to prevent excessive lubrication of the valve and guide (Fig. 7).

Fig. 7 - Valve Stem Seals - 283 Cu. In. Engine

The vacuum distributor advance tube is connected directly to the intake manifold instead of to the carburetor throttle body. With the full manifold vacuum, spark advance at the idle is increased. This results in a faster burn rate, and less heat to be dissipated through the cooling system. This vacuum advance hose must be disconnected when setting timing. Do not forget to reconnect the hose after setting timing.

The special optional fuel injection engine rated at 290 horsepower, introduced in mid-1958, again is available. This is the same engine as the high performance Corvette fuel injection engine equipped with solid valve tappets, special camshaft and special bearings.

Like its Corvette engine counterpart, the special optional fuel injection engine has coolant passages in the cylinder heads that encircle the base of the spark plugs.

On all 283 engines equipped with power steering and power brakes, any service operation which requires lowering the rear of the engine, such as transmission removal, etc., allows the power steering filler neck to contact the brake master cylinder, resulting in cracking around the base of the filler.

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