Chevrolet High Value V6 (LX9 / LZ9)

General Motors' last pushrod 60° V6 — 3.5 and 3.9 litres, in the Impala, Malibu, Monte Carlo, G6, Uplander, Rendezvous, Aura, Relay and Vue. It is the direct descendant of the 3100 and 3400, and its faults are largely theirs.

Do not confuse it with the High FEATURE V6, which is a different engine entirely: overhead camshafts, 3.0 and 3.6 litres, sold at the same time in some of the same cars. The names differ by one word and the engines share nothing. Establish which is fitted before quoting anything, because a 3.5 pushrod and a 3.6 DOHC in the same model year are not variants of each other.

The family fault is the intake manifold gasket, inherited from the 60° V6 line: a composite gasket that the metal either side works loose as the engine heats and cools until coolant escapes — or, worse, gets into the oil. Coolant in the oil on one of these is the gasket until proven otherwise, and the revised gasket with thread-locked bolts is the repair rather than a head job.

The 3.9 is unusual and worth knowing about: it is a pushrod V6 with variable valve timing, achieved with a single phaser on the camshaft. It is the only variable-timing engine in this family, it sets correlation codes when the phaser or its oil supply fails, and a procedure written for the 3.5 does not cover it.