Quote:
Originally Posted by Mike Taylor 3601
It isn't the spring pressure breaking parts,95% of valve train failures aren't from excessive spring pressure,they are caused by too low of spring pressure which lets lifter bounce and not follow cam lobe, which breaks ceramic lifters or axles out of roller lifters,pops the heads of valves,burrs keeper grooves, beats seats out wide,wears guides out, stretches timing chains, pops rocker studs and rockers in two.
Every lobe has a limit no matter how much spring you have there is a RPM which it becomes unstable and starts self destructing the valve train.
Larry may have just had lifter get fatigued or damaged some how and caused failure.
Mike Taylor 3601
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Not exactly a complete analysis. While "not enough" valve spring pressure can cause failures as you describe because of lack of control, I would also have to say that the allowed increased spring pressure has promoted running the engines at a much higher rpm range and demanded much more radical camshaft dynamics which have contributed to more failures than not enough valve spring pressure. The stresses on valve train components increase geometrically with the rpm, which contributes to parts failure more than the "not enough" spring pressure as you point out. Also, without the increased spring pressure, having to resort to parts like the ceramic lifters or tool steel lifters would not have been necessary. The camshaft manufacturers are smart guys and will produce profiles that work with whatever pressures are available, so you think that they are not pushing the limits of design to take advantage of the increased pressures and increasing engine speeds and ramp events accordingly? They also pushed limits in the same way when we ran OEM valve spring pressure, but the spring pressure limitation kept the engine speeds lower and camshaft dynamics softer so parts were not stressed nearly as much. The snowball effect of the consequences of that one rule change has escalated the cost of stock eliminator more than any other, and it simply was not necessary.