Clevite's engineers have also learned an even more revealing piece of information regarding piston ring performance. Typically, pistons have three rings - two top "compression" rings and a third, usually multipiece, "oil" ring. Through sophisticated testing, it was discovered that the roles of these three rings are not what they were previously thought to be. They learned that 90 percent of the role of the top ring is compression control, with 10 percent being oil control, and these percentages are reversed for the third, oil control ring.
As for ring design, many factors come into play. Ring coatings, base material (gray iron, ductile iron, or steel, for example), bevels, twist, clearances, even oil ring design, all contribute to performance and efficiency in many different types of engines. And remember, in an engine running at 6,000 rpm, each cylinder is seeing a combustion event 50 times a second! So, ring design is a very precise science and must be exactly right for a particular engine family.
Head gaskets are extremely critical in engine building and can vary in design and function. Many factors come into play in determining the optimum head gasket design for a given engine. Head and block materials, compression ratios, sealing widths, surface finishes, and even combustion chamber shape can play a role in the demands placed on head gaskets. We received Victor Reinz Nitroseal graphite-type head gaskets. This type of gasket consists of Teflon-coated graphite clinched to a perforated steel core with a stainless steel flange. The stainless steel flange resists damage from combustion gases and pressures, and the graphite facing results in more efficient heat dissipation in order to reduce the amount of heat transferred to the combustion seal.
In the next issue of 4WD&SU, we will discuss machining, balancing, and head porting, as well as tell you about some of the more important points of fine engine building.