CREATE TABLE table_69620 ("Year" FLOAT, "Entrant" TEXT, "Chassis" TEXT, "Engine" TEXT, "Points" FLOAT)

Name the engine with chassis of maserati 250f and entrant of luigi piotti with year less than 1957
SELECT "Engine" FROM table_69620 WHERE "Chassis" = 'maserati 250f' AND "Entrant" = 'luigi piotti' AND "Year" < '1957'
SELECT "Engine" FROM "table_69620" WHERE "Chassis" = 'maserati 250f' AND "Entrant" = 'luigi piotti' AND "Year" < '1957'