All 1956 U.S. Mercury models were powered by the V8 breathing through a four-barrel carburetor. At the beginning of the model year, a version with 8.0:1 compression ratio powered Mercury cars with manual transmissions (including three-speed plus overdrive), while a version powered cars with automatic transmissions. The 225-horsepower version had an 8.4:1 compression ratio. Later in the model year, a version with 9.0:1 compression ratio became available. All 1956 Mercury engines had gold-painted blocks and heads. The 210-horsepower version had red valve covers and air cleaner, while the 225-horsepower version had blue valve covers and air cleaner. The 235-horsepower version had argent silver valve covers and air cleaner. A dealer-installed "M 260" engine kit was released in January 1956. The kit consisted of a hotter camshaft, revised cylinder heads, and an intake manifold mounting two four-barrel carburetors. The kit was advertised as boosting the Mercury 312 V8 to .