CREATE TABLE table_63836 ("Model" TEXT, "Engine" TEXT, "Displacement" TEXT, "Valvetrain" TEXT, "Fuel system" TEXT, "Max. power at rpm" TEXT, "Max. torque at rpm" TEXT, "Years" TEXT)

What is the displacement for the petrol engines model?
SELECT "Displacement" FROM table_63836 WHERE "Model" = 'petrol engines'
SELECT "Displacement" FROM "table_63836" WHERE "Model" = 'petrol engines'