Chevrolet Monza headlight bulb sizes include H6024 and H4651 for high beam applications and H6024, H4656, and H4652 for low beam applications. The replacement chart covers 1975 through 1980 production years with corresponding bulb size specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The H6024 is a 7-inch round sealed beam unit operating at 12V and conforming to ANSI standards for the US and Canadian markets. On the Chevrolet Monza, it served as both the high beam and low beam headlight for the 1975-1976 model years, as well as the 2-headlamp configuration in 1980.
The H4651, H4652, and H4656 are all 4x6-inch rectangular sealed beam units operating at 12V under the same ANSI standard. Their presence across the 1977-1980 model years reflects a shift from the round H6024 format used in 1975-1976.
All four bulb types covered in these specifications are sealed beam units, meaning the lens, reflector, and filament are fused into a single assembly. When a filament fails, the entire unit requires replacement rather than just an internal bulb.
The 1979 Monza low beam headlight uses the H4652, which is a variant of the H4651 used for the high beam position. Although both share the same 4x6-inch rectangular sealed beam format, they are distinct part numbers and are not interchangeable between beam positions.
The 1980 Monza carried two distinct headlamp system configurations. The 2-headlamp system used the H6024 round sealed beam for both high and low beam functions, while the 4-headlamp system used the H4651 for high beam and the H4656 for low beam.
The H4651 and H4656 share the same physical 4x6-inch rectangular sealed beam format and voltage rating, but they are separate ANSI-designated units assigned to different beam functions and are not interchangeable with each other.