Table: engine_specs_2
Columns: engine_model
engine_displacement
valvetrain
max_power_kw_ps
rpm_for_max_power
max_torque_nm_ft_lbf
rpm_for_max_torque

Question: What is the valvetrain with an engine model that is engine model?
SQL: SELECT "valvetrain" FROM engine_specs_2 WHERE "engine_model" = 'engine model'