Posted by Todd Somers on Sunday, February 16, 2003 at 5:06PM :
The diesel engine that has been refered to in the posts below was designed in the late 1970's by Onan Coproration of Minneapolis, MN. At the time Onan was a part of the McGraw-Edison Company. When this line of engines was designed by Onan they were called the "L" series and consisted of two-, three-, four-, and six-cylinder in-line four stroke engines with a common bore of 89mm (3.5in) and stroke of 92mm (3.62 in), giving .57 liters (35cid) per cylinder. The engines were designed for a variety of industrial and power generation applications. Engine speeds up to 3600 rpm for a continous duty cycle were a significant design feature. According to goverment statistics, at the time of the introduction of the "L" series engines Onan was the largest domestic producer of diesel engines under 50 hp. The engines were rugged and well designed with the four cylinder engine having five main bearings and the six cylinder engine having seven. The engines were carefully designed. The naturally aspirated engines were produced first, with turbocharging being planned as a revision for higher horsepower applications. The Onan Huntsville, Alabama manufacturing plant was used to build these engines. This plant was managed by a fiesty Scotsman who was a very interesting fellow and enjoyable to be around. The engines proved to be extremely durable and reliable. After Onan was purchased by Cummins, the designation name of the engine was changed from the "L" to the Cummins designation of "A". Thus the Onan L634DT engine became the Cummins 6AT3.4. The production of these engines was phased out when the design could no longer meet the ever increasing air quality standards.
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