What was the bore of the Ford Model T engine in inches?

The bore of the Ford Model T engine was 3.75 inches.

Ford’s inline-four used a 3¾-inch cylinder bore and a 4-inch stroke, producing about 177 cubic inches, or 2.9 liters, of displacement. The slightly longer stroke made it a relatively long-stroke engine by modern standards and helped it deliver useful low-speed pulling power.

The engine was an L-head, or flathead, design: its valves sat beside the cylinders in the engine block rather than in a separate overhead cylinder head. All four cylinders were cast into one block, a monobloc arrangement that suited Ford’s emphasis on repeatable, economical manufacture.

A common mix-up is to reverse the bore and stroke. The 3.75-inch figure is the bore—the cylinder’s internal diameter—while 4 inches is the distance the piston travels. The engine’s low compression ratio, about 3.98:1 in most examples, also helped it run on the relatively low-octane fuel available in its day.