Chevrolet L67

The supercharged 3800 — an Eaton M90 Roots blower on the Series II bottom end, 240 hp, in the Park Avenue Ultra, Riviera, Bonneville SSEi, Grand Prix GTP, Impala and Holden's Monaro.

It is not an L36 with a supercharger added. The compression ratio is lower and the pistons are different, so the two are not interchangeable in either direction — which is exactly the swap people attempt.

The fault to know is the supercharger coupler, because it is routinely misdiagnosed as an engine knock. A rubber-and-plastic isolator drives the rotors from the snout; it hardens and breaks up, and the rattle it makes at idle sounds like a bottom-end problem in a car old enough for that to be believable. It is a cheap part and a bolt-on job, and condemning the engine instead is the expensive mistake this page exists to prevent.

The supercharger also has its own oil, in the snout, and almost nobody changes it. There is no service light for it and no dipstick anybody looks at; run dry, the snout bearing takes the unit with it. Beyond that, the boost bypass valve and the supercharger belt tensioner account for most complaints of lost boost.

And it shares the family's intake manifold gasket and the plastic upper manifold cracking around the EGR passage — which manifold revision a car carries matters more than its mileage.