Commercial trucks have been roaring up and down America’s roadways for more than a century. During that time, dozens of engines have served duty powering the brands we all know and love such as Freightliner, Mack, Peterbilt, Kenworth, Western Star, and International. Some of these power plants have been good, others great—and some of them haven’t been so great, even ugly…reason enough for us to put together a compilation highlighting the best and worst engines ever produced. Good, bad, and ugly, we at Big Bear Engine—and in conjunction with our sister company, Capital Reman—rebuild many of the Class 8 engines that follow, and we’ve drawn from our 40-plus years of hands-on experience to present this list to you.

The Best

1. Cummins 855 Big Cam

Basic Engine Highlights

Earning its name from having a larger-than-average, 2.5-inch diameter camshaft, the 855Big Cam 855 Cummins Diesel Engine Big Cam replaced the 855 ci small cam of the 1960s (which was graced with a 2-inch diameter camshaft). Reliable doesn’t even begin to describe this engine. But on top of being steadfastly durable, it was fuel efficient and powerful. This is the engine that all but singlehandedly allowed Cummins to go from a 29-percent share of the Class 8 market in 1975 to 63-percent by 1983. One of the major high marks for the 855 Big Cam occurred in 1980 with the release of the 475 hp, compound turbocharged Big Cam II, a very big deal at the time.

Biggest Pros

The list here is long and distinguished, but the 855 Big Cam’s largest selling point in itsClass 8 Semitruck Cummins 855 Big Cam production days was its promise of best-in-class fuel economy. Following the oil crisis of 1973, fuel efficiency became the biggest priority in freight transportation. Next comes the 855 Big Cam’s million-mile reliability, its demand flow cooling system (which only cooled areas of the engine where cooling was needed, thereby saving energy and allowing more horsepower to be used for the task at hand), and its abundance of low-rpm torque. The Cummins 855 Big Cam was also notably more powerful than its small cam predecessor, mainly due to its use of the infamous “Top-Stop Injectors.” Lastly, this engine responds very well to modifications, making it a hit among owner operators.

Few Downsides

The rap sheet here is short and sweet—just as you’d expect from one of the best dieselCummins 855 Big Cam Reduced Drain Flow Injectors engines ever produced. Cold-start issues are rampant for any Cummins 855 Big Cam operating in cooler climates, but it’s a problem that can easily be solved through the use of a block heater or oil immersion heater. Later models, such as the New Big Cam IV, came with the notorious STC (Step Timing Control) technology and the 88 Big Cam IV—the last version of the 855 Big Cam—had very problematic Reduced Drain Flow (RDF) injectors. Other than that, there are very few negative talking points surrounding this engine platform.