400 4-bbl V8

Years 1970–78 Models 3

Also described as 400 4-bbl "6.6 Litre" (180/185 hp)400 4-bbl400 4-bbl (300 hp)

Documented applications

Firebird / Trans Am

1970–1978 Confirmed

Formula 400; T/A 6.6 base 400 in ’77–78
1975–1978 Confirmed
1977–1978 Confirmed

Base T/A engine

Grand Prix

1973–1977 Single-source

Same caveat as L75

GTO

1971 Single-source

GTO standard engine's UPC per corporate lists

This page aggregates every documented appearance of L78 in the Pontiac reference. Confidence and citations are shown per application — the same code can be better documented in one year than another.