what was the engine when ken downing drove an entrant from connaught engineering?
CREATE TABLE "teams_and_drivers" (
  "entrant" text,
  "constructor" text,
  "chassis" text,
  "engine" text,
  "driver" text,
  "rounds" text
);
SELECT "engine" FROM "teams_and_drivers" WHERE "driver"='ken downing' AND "entrant"='connaught engineering';