Chevrolet L05 (5.7 TBI)

The 5.7 in throttle-body injected form — the last widely fitted version of the first-generation Chevrolet small block, in the Caprice, Roadmaster, Fleetwood, the GMT400 Tahoe and the Hummer H1. The LS (Gen III small block) that replaced it shares almost nothing with it but the bore spacing.

Throttle-body injection is the thing to understand about it. There are two injectors on top of the manifold rather than one per cylinder, so the fuel is distributed by the intake runners exactly as a carburettor's was — which means a vacuum leak, a sticking IAC valve or a tired distributor produces symptoms that read as fuel-mixture faults and are not. Diagnose air and spark before fuel on this engine, which is the opposite of the habit a port-injected engine builds.

The distributor is the recurring item: its shaft bushing wears and the ignition timing wanders, and the optical or magnetic pickup inside fails intermittently with heat. The intake manifold gasket is the family fault it shares with GM's V6s of the era, and by this age the rear main seal has usually been dealt with once.

The 5.0 of the same family is on this page too, because it is the same engine one bore smaller and everything here applies to it: L03 is its throttle-body form in the Caprice and Roadmaster, L30 its later Vortec form in the Express and Savana vans. The three characters on the block are what separate them, not anything you can see.