And it will only get worse projected future oilspec revisions will likely reduce ZDDP content even more.įor in-service engines, consider running cam and lifterprelube in the oil all the time, not just during break-in.
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. 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 ofZDDP in street-legal, gasoline-engine motor oils. What we know forsure is that the most serious complaints have cropped up within the lastthree years or so, around the time that major changes occurred in boththe flat-tappet manufacturing industry and in the formulation ofpassenger car and light-duty truck motor oils.įerner adds, "The zincreacts with the cam lobe's iron surface. What's the real source of the failures, and more importantly,rather than whining over spilled oil, what can be done to minimize theoccurrence of these failures? Various parties have blamed camshaftmanufacturing quality control, inferior flat-tappet lifters, theaggressiveness of today's modern cam profiles, and engine oilformulation as the primary factors behind the failures. As one engine builder puts it, "I've failed morecams in the last three years than I have in the last 30." There areseveral theories as to the primary causes of these failures, and withall the usual finger pointing and blame game such unfortunate episodesinevitably generate, the result has been a muddying of the waters that'sleft average hot rodders confused and uncertain as to the best course ofaction. For the last several years, many engine builders and individual hotrodders have experienced a raft of seemingly unexplained flat-tappetcamshaft lobe failures.
0 kommentar(er)
