BMW Valve diameter

All M series engine valves are 6mm stem diameter
N52, S65 series 5mm stems
N52K, N53, N54, N55 and S55 series 5mm intake, 6mm exhaust

M50B20 vanos and non vanos, M52B20 – intake 29.4, exhaust 26.4, 6mm stem
M52TUB20, M52B22 – intake 29.4, exhaust 26.5, 6mm stem
M50B25 vanos and non vanos, M52B25, M52B28 – intake 32.4, exhaust 29.4, 6mm stem
M52TUB25, M52TUB28, M54B25, M54B30 – intake 32.4, exhaust 30.0, 6mm stem

S50B30, S52B32 – intake 29.4, exhaust 26.4, 6mm stem
S54B30 – intake 34.5, exhaust 30.0, 6mm stem
S65B40 – intake 34.0, exhaust 29.3, 5mm stem
S55B30 – intake 30.4, exhaust 26.6, 5mm intake stem, 6mm exhaust stem

N52K25, N52K30, N53B25, N53B30 – intake 27.7, exhaust 26.6, 5mm intake stem, 6mm exhaust stem
N54B30 – intake 27.7, exhaust 26.6, 5mm intake stem, 6mm exhaust stem
N55B30 – intake 30.4, exhaust 26.6, 5mm intake stem, 6mm exhaust stem
N52B25 – intake 32.2, exhaust 27.0, 5mm stem
N52B30 – intake 34.2, exhaust 29.0, 5mm stem