The ED was the first diesel built in-house by an American truck manufacturer and it was a mighty good first shot. With a 4.375 inch bore and 5.75 inch stroke, it made 131 horsepower at 2000 rpm from 519 cubic inches. The seven-main crankshaft with insert bearings was more than able to carry the 382 lbs-ft of torque that came in at 1300 rpm. The c ylinders were dry sleeved and this engine was claimed to be the first HD engine to use split-skirt aluminum pis tons. Another first claimed was a tongue-and-groove connecting rod cap lock. Mack was one of the first to have water cooling around the injector nozzle and used an extra long injector for maximum cooling. Like many diesels of the era, it had two cylinder heads, each covering three cylinders. The engines generally used Bosch inline injection pumps and Ex-Cell-O injectors.
Visible in this cutaway are the crossflow head, with the Lanova power cell, the tongue-and-groove rod caps, dry cylinder liners and split-skirt pistons. The crankshaft main journals were 3.5 inches in diameter. The engine weighed nearly 2,000 pounds.
Some companies often step ahead of their competition. At times, that’s a step too far and requires two steps back, but not this particular time. When Mack Trucks Inc. embarked on the road towards diesel engines in 1927, they were charting the course for an entire industry and took no steps back. Their careful research yielded a viable truck diesel that was successful within the limitations of the market then. Mack was one of the few truck manufacturers to build their own engines. They weren’t the first company to offer a diesel option in big trucks, though they were at the forefront of those that did, but Mack gets the nod for being the first truck company to build their own diesels in-house.