The Ford Y-Block 312 is the largest Y Block engine of its era and is acclaimed for producing over 300 hp if a Paxton supercharger is added. Initially released in the model year 1956 for high-end Mercury and Ford cars, the Ford Y-block 312 featured a 3.8 inch bore and 3.44 inch stroke with a short 6.254 inch connecting rod. At the start of the model year, all Mercury cars made in the United States were powered by the Ford Y-Block 312, with a 3-speed plus overdrive manual transmission, 210 hp, and a compression ratio of 8.0:1. There was also a version of the Y Block 312 with 225 hp and an automatic transmission released early in the model year, while later in the year a 235 hp edition with 9.0:1 compression was released.
The final year the Y block 312 appeared in a Ford car was 1957, while it was continued to power Mercury cars until 1960. During these years, it was available with several options, including a 2-barrel carburetor, a 4-barrel carburetor, two 4-barrel carburetors, or a McCulloch (Paxton) supercharger.
Telling the difference between a Y Block 292 and Y block 312 is difficult since they’re nearly identical on the outside. The quickest and most efficient way to tell the difference is to take a look at the flywheel flange on the crank shaft. If you see a dot on the outer edge of the crank shaft, then you probably have a 312.