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HK-HG Monaro / GTS

1968-1971 / Coupe / Australia

All HK-HG Monaro / GTS problems All workshop issues
Common Engine, Chevrolet V8 (327ci / 350ci)

Rochester Quadrajet Carburettor Issues

Symptoms

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

Cause

The Rochester Quadrajet (Q-jet) is a complex 4-barrel carburettor with small primary jets and large secondaries. The primary metering rods and jets wear, the accelerator pump deteriorates, the float level drifts, and the power piston can stick. The Q-jet's small primary circuits are sensitive to dirt and fuel quality. Ethanol in modern fuel attacks the original rubber accelerator pump and needle valve seat.

Fix

A full Q-jet rebuild with a quality rebuild kit ($80-150) addresses most issues.

The key is getting the float level correct, an incorrect float level causes almost all Q-jet running problems.

Alternatively, many owners replace the Q-jet with a Holley 4-barrel or Edelbrock Performer carburettor ($400-800).

These are simpler to tune and maintain, though they're not period-correct for concours judging.

Cost mentioned in fix
$80-150$400-800

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

Overheating Under Load

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