The first Chevy V8 was not what many think.
Just after Chevrolet became part of GM in the 1917, it produced a V8 powered, 4 passenger roadster and a 5-passenger touring car. The year was 1918. The engine was an OHV, 288 cuin, 35hp, V8.
Admittedly, the more common answer for this question is: 1955 when the first small-block V8 appeared in the Chevrolet passenger car and, later in the year, in the Corvette.