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Reply to "Camshaft failure"

Here in the US the auto manufacturers were mandated to warranty their emissions systems for 100,000 miles; at the same time the level of ZDDP was drastically reduced in gasoline engine motor oil sold in the US. This was necessary because (as previously mentioned) ZDDP poisons catalytic converters, or shortens their life.

Roller tappets were already being employed by the auto manufacturers; they had gone into service years earlier (1980s) when the levels of ZDDP had been previously reduced to extend the life of catalytic converters. But with the 100,000 mile warranty looming in the near future, the auto manufacturers introduced distributorless ignitions and crankshaft driven oil pumps too (no distributor gear needed). The changes they made to the engines indicate the auto manufacturers knew the flat tappets & distributor gears needed ZDDP; end of argument! The government & auto industry didn't bother to inform the owners of older vehicles however.

There were 4 other factors that contributed to the camshaft & distributor gear failure problems we experienced more than a decade ago.

(1) Advances in camshaft grinding equipment made it possible for aftermarket cam grinders to grind street cams that had lift rates similar to the lift rates of race cams in the 1970s.

(2) With the industrialization of some of the Asian nations one or more of the camshaft manufacturers began sending some of their manufacturing over-seas, where quality control wasn't up to North American & European standards.

(3) A decade or so after the advent of the roller cam (in the 1980s) some enthusiasts had never learned how to properly break-in a flat tappet camshaft.

(4) The camshaft manufacturers began selling retro-fit roller cams for engines originally equipped with flat tappet cams. And none of them seemed to understand what materials the distributor gears should be manufactured from to compliment these cams. Some of them were selling bronze gears for street applications! Holy Cow!

All of these factors came to a head around the year 2001, and an unusually high rate of flat tappet camshaft failures & distributor gear failures began occurring.

As an interim measure some of us switched to using diesel motor oils in the mid 2000s, I'm not aware of anybody having any problems with them. But that interim solution didn't last too long, because within a few years the ZDDP level of diesel motor oil sold in the US was also reduced.

It took a few years, but eventually the camshaft grinders, the SEMA industry, and the motor oil industry sorted stuff out. Motor oils with a higher content of ZDDP have been introduced as oils for race engines or older engines, quality control has improved, Crane Cams made steel distributor gears available for cams ground on their steel cores, and the public has been educated about breaking-in flat tappet cams. The folks who manufacture or sell camshafts are better educated regarding the spring rate limitations of flat tappets, and Harvey Crane's concepts of hydraulic intensity, minor intensity and major intensity are better understood in terms of how they impact valve train wear.

Nobody has ever admitted guilt, all the companies involved want to blame other portions of the industry, nobody wants to admit liability, but we don't hear of failures like we used to.

-G
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