Previously, we’ve brought you the world’s largest four-stroke engine, spark-ignited engine, the monstrous Wartsila 18V50DF, which runs on compressed natural gas (with a diesel variant as well). Then there’s also the Lycoming XR-7755 radial engine, which may very well be the largest piston-powered gasoline engine ever. But when it comes to gasoline powered inline engines, there’s not much in the way of large.
Marine engines, while are often large inline or V engines, are not usually powered by gasoline. So it took a little digging to find something that was large, a traditional inline configuration, and powered by gasoline. And when we found it, it wasn’t anything modern, but rather something back from World War II.
Known as the “83-Footer”, these wooden ships were designed and built during World War II, originally for the US Coast Guard for Convoy and Anti-Submarine duty. Powering these unique vessels was a pair of unique engines. Enter the Sterling Engine Company TCG-8 “Viking II” engine.
The TCG-8 was an inline-eight-cylinder, four-stroke engine, which consumed gasoline… and lots of it. An undersquare design, the engine featured an 8.00-inch bore and 9.00-inch stroke, for a total displacement of 3,619.1 cubic inches, or 59.3 liters, making it one of, if not the largest inline gasoline engine in the world.
The engine itself was relatively compact, at 12 feet, 2-9/16 inches long and only 44-9/16 inches wide, which allowed the two engines to fit comfortably side-by-side in the 83-footer’s hull. Housed in a gray-iron block, the crankshaft was a forged chromoly steel piece, with separately attached counterweights, which were affixed to the crankshaft via a dovetail and bolts. There were nine traditional babbit-style bearings, 4.00 inches in diameter, which measured 2.75 inches in width on eight journals, with the thrust bearing measuring a beefy 3.437 inches wide.
The rods were 18-inch carbon-steel I-beam behemoths, 3.125 inches thick, weighing-in with a 6.5 lb small end, and a 17.75-pound big end. The 8.00-inch diameter pistons were 8.719 inches tall and made from aluminum, with a 4.719-inch compression height. There were four piston rings utilized – two .250-inch-thick cast iron compression rings, and two 9/32-inch-wide oil rings, also made from cast iron. A 2.00 inch wristpin held the massive 19.75-pound pistons in place, while the 1.50-inch-diameter camshaft was made up of three sections and had a surprisingly low 0.420 inches of lift.
Up top there were four cast-iron cylinder heads used, with each cylinder head housing two combustion chambers. Each cylinder had its own exhaust port, while each pair of cylinders shared an intake port. The heads were a four-valve design, each cylinder having two 2.906-inch intake valves, each with a massive .557-inch-diameter valve stem. In a unique configuration, one exhaust valve per cylinder was actually larger than the intake valves, while the other was slightly smaller, with the dissimilar valves measuring 2.910 inches and 2.901 inches.
The engine only had a compression ratio of 5.0:1, and as such was able to run on incredibly low octane gasoline. The ignition system operated with two distributors and four coils per engine. Each cylinder head had four spark plugs (two per cylinder) and ran a surprisingly small spark plug gap of .025-inch.
All of this combined to produce approximately 600 horsepower at 1,200 rpm, per engine, which was good for approximately 18.5 knots, while consuming a thirsty 120 gallons of gasoline per hour (60 gph per engine). Cruising speed was 1,000 rpm, which pushed the 83-Footer to 12 knots and lowered the combined fuel consumption to 100 gph.
While not very efficient by today’s standards, back in the 1940s and ‘50s the Sterling TCG-8s were beasts which helped make the 83-Footer a capable vessel that played a critical role in our nation’s maritime history.