This paper presents a background of the cam and tappet wear problem encountered by the automotive industry during the evolution of the modern overhead valve V-8 engine. Investigation of the numerous factors affecting this problem revealed that engine oil composition was of major importance. The development of a test technique to determine the adequacy of engine lubricant antiscuff properties is described and evidence of correlation with field experience is presented.
This test technique was accepted by Section G-IV of Technical Committee B of ASTM Committee D-2 in October, 1959 as Test Sequence IV. This test was one of a series of test sequences to be used for evaluating oils for API Service MS.
Shortly after the end of World War II, the modern V-8 engine was introduced to the American motorist. These new engines, characterized by stroke-bore ratios under one, compact combustion chambers, push-rod operated overhead valves, and rigid crankcase construction provided significant improvements in performance, quietness, and smoothness of operation. These qualities were widely welcomed by the customer.
It wasn't long, however, before the greater vehicle performance was more than just welcomed; it became a demand. These engines rapidly evolved in size and performance to the efficient, flexible, powerplants they are today. In the process of this development, however, there were some growing pains. This paper will deal with one of these problems.