Thread: Single partern and dual pattern cams

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This may sound like a sinple question, but I'm a simple person that would like to know the difference between a single patten cam and a dual pattern cam ? and what applications the two would be used for ? Also is and anti pump lifter considered a solid lifter ?

Single pattern has the same duration and lift on the intake and exhaust lobes. Dual pattern has a different grind intake to exhaust, with the exhaust favored for the bigger numbers until you get to super radical cams. Then the intake gets bigger. According to some experts, it's much ado about nothing. Read this take on it by Ron Iskenderian......scroll down to Tech Tip 2003....
http://www.iskycams.com/techtips.php

An anti pump up lifter is hydraulic (and automatically adjusts the valve lash) as opposed to a solid lifter which has no operating parts inside the lifter shell. Valve lash is set with adjustable pushrods or with the rocker stud nut or, on a shaft mounted system, by an adjusting stud and nut on the rocker itself.

Popular Hot Rodding has a pretty good explanation of the workings of an anti pump up hydraulic lifter......

"Anti pump up lifters are intended to fix a problem that can occur toward the top 25 percent of the engine's rpm range. What happens is that the spring starts to lose full control of the valvetrain and separation between various components takes place. This, as far as the lifter is concerned, looks like lash, so the lifter does it's job and takes it up. When the valve now tries to close, the lifter, which is now a little too long, holds the valve off its seat and heavy-duty power loss takes place. For many years, the accepted fix for this was an anti-pump-up lifter, which was a much leakier, faster-collapsing lifter that allowed the valve to physically close unimpeded. But it also collapses easier and consequently cuts valve lift. The real fix is a spring with better control. If valvetrain noise is of little or no concern, then a solid cam is the way to go, as there are no worries about hydraulic lifter collapse."