Chevrolet Gen II small block (LT1)

General Motors' second-generation small block — the 5.7 of the C4 Corvette, the fourth-generation Camaro and Firebird, and the Caprice, Roadmaster and Fleetwood.

GM later reused the name. The 6.2 in a 2014-onward Corvette or Camaro is also an LT1, and it is the Gen V engine — a completely different design. Three characters, thirty years apart, and nothing shared but the badge, so establish the year before applying anything written about an LT1.

Its defining feature and its defining fault are the same part: Opti-Spark. The distributor is driven off the front of the camshaft and sits behind the water pump, low down at the front of the engine. A weeping water pump drips straight into it, and the optical sensor inside fails — producing a misfire, a stall, or a no-start that comes and goes with damp. On a Gen II, an intermittent misfire is Opti-Spark until proven otherwise, and the water pump has to come off to reach it, which is why the labour looks disproportionate to the part.

The other item peculiar to this engine is its reverse-flow cooling, which sends coolant to the heads first. It works, and it makes the system less tolerant of air pockets: a Gen II that runs hot after a coolant change very often just needs bleeding properly.

The Gen II LT4 of the 1996 Corvette Grand Sport is a higher-output version of this engine, and is not the supercharged Gen V LT4 either.