That creates a sacrificialchemical coating strong enough to keep parts separated to reduce thewear.” Although great for keeping a flat tappet alive, as an engine agesand develops blow-by, some of the additives flow out the exhaust wherethey can degrade oxygen sensor and catalytic converter performance.Faced with ever more stringent emissions standards and the governmentalmandate for extended emissions-control- system warranties, the OEMs gottogether with the motor oil makers and decided to reduce the amount of ZDDP in street-legal, gasoline-engine motor oils.Within about a three-month window, twoout of the four went out of business.
Most of these inferior lifters had questionablemetallurgy, a poor surface finish, and an improper crown radius. Major cam companies, including Compand Crane, maintain that they never sacrificed lifter quality or soldinferior lifters.
“We figured we were better off selling nothing thanselling junk,” says Crane’s Chase Knight.
After all, theyweren’t needed with modern roller lifters and overhead-cam followers.
The reduction first started in the mid-’80s, and it has been a gradualprocess, but the latest API SM and GF-4 specs have reduced ZDDP contentto such an extent that the new oils may not provide adequate protectionfor older, flat-tappet-equipped vehicles running nonstock, performancecams and valvetrains.
According to Mark Ferner, team leader for Quaker State Motor Oil Research and Development, “Even stock passenger cars cansee pressure in excess of 200,000 psi at the point of flat-tappet/camlobe contact.” To prevent excess wear, traditional motor oil included agenerous dose of antiwear additives, primarily zinc dialkyldithiophosphate (ZDDP).