Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_name_22 ( max_speed__km_h_ INTEGER, quantity_built VARCHAR, year_built VARCHAR )

### Question ###
What is the max speed of the unit with an 8+4 quantity built before 1971?

### Accurate SQL ###

SELECT SUM(max_speed__km_h_) FROM table_name_22 WHERE quantity_built = "8+4" AND year_built < 1971