HK-HG Monaro / GTS

1968-1971 / Coupe / Australia

All HK-HG Monaro / GTS problems All workshop issues

Critical Engine, Chevrolet V8 (327ci / 350ci)

Overheating Under Load

Symptoms

Temperature gauge climbs on highway drives, particularly towing or climbing hills. May push coolant out the overflow. Engine pings (detonation) under load.

Cause

The 327 and 350 V8s generate significant heat, and the factory cooling system was designed for 1960s conditions. The original radiator may be partially blocked. The clutch fan loses efficiency with age. The thermostat may be stuck or the wrong rating. In the Monaro's engine bay, heat soak from the exhaust manifolds further stresses the cooling system.

Fix

Have the radiator recored or replaced with a 3-core brass or aluminium unit ($400-800).

Fit an electric thermo fan ($150-250).

Ensure the thermostat is 82°C (180°F) and functioning.

Check the water pump for leaks and cavitation.

Consider ceramic-coated or wrapped exhaust manifolds to reduce underbonnet heat.

Cost mentioned in fix

$400-800$150-250

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Other known issues

Critical Engine, Chevrolet V8 (327ci / 350ci)

Intake Manifold Gasket Leaks

Coolant leak at the front or rear of the intake manifold. Coolant may drip externally or, worse, leak internally into the engine oil. May also cause a vacuum leak, resulting in rough idle and poor fuel economy.

Common Engine, Chevrolet V8 (327ci / 350ci)

Rochester Quadrajet Carburettor Issues

Hesitation on acceleration (bog), flooding, fuel smell, hard starting when hot, black smoke, erratic idle.

Common Engine, Chevrolet V8 (327ci / 350ci)

Hydraulic Lifter Noise

Ticking or clattering from the top of the engine that varies with RPM. May be audible at idle and disappear at higher RPM, or vice versa.

Common Engine, Holden Six (186ci) and V8 (253ci)

Oil Leaks, Rear Main Seal

Oil drips from the bellhousing area. Oil accumulates on the underside of the engine and transmission.

Common Engine, Holden Six (186ci) and V8 (253ci)

Valve Train Wear (253 V8)

Ticking or clattering from the top of the engine. Reduced power.

Common Transmission

Muncie 4-Speed Synchro Wear

Grinding on gear changes, particularly second and third gear. Difficulty selecting gears under load.

View all 18 HK-HG Monaro / GTS problems