Your intake and exhaust valves act as dams that control your engine’s ability to breathe. In a perfect world, your engine wants the valves to disappear in an instant to allow it to start flowing air, and then instantly reappear on their closing stroke like magic. But, thanks to the laws of physics, that’s impossible — with the technology we have available now anyway.
There’s a shaft and stud-mounted rocker arm series out there with a unique design that stands out among the others. It has been continuously revised over the years, with each design getting us a step closer to accomplishing that impossible goal. We had the chance to speak with Allan Bechtloff of Crane Cams to get a quick history on Crane’s “Quick-Lift” design found in their Gold Race series rocker arms and how it was discovered.
“Harvey Crane was always an old school cam guy, he didn’t want the rocker arm to interfere with whatever he was doing with the camshaft, and nothing outside of his control was going to be introduced into the system,” explains Bechtloff. “If he said he wanted the rocker arm to have a certain ratio, it would have that static ratio from the beginning of the valve event to the end of the cycle. If the rocker deflected or bent in any way, he would overcompensate during the manufacturing of the rocker arm to make it as stable as possible.”
Example: Y = 1.7 | X = 1.0 | Rocker Arm Ratio = 1.7
“When this style rocker arm was first released and before we had a name for it, whether by accident or design, it was immediately noticed that engines running this style rocker had more pickup and more power than others, but no one really understood why,” Bechtloff continues. “Many people assumed it was just because the new rocker was more rigid. Once people really started to investigate this phenomenon it was discovered that it wasn’t just its rigidity, but the rate at which the valve moves had been slightly changed as well, and the engine liked it.”
Essentially, the concept behind Crane’s Quick-Lift technology is to accelerate the valve off of the seat faster, slow it down at mid-lift, and then close the valve as quickly as possible.
“It’s really about moving around key positions on the rocker arm during the manufacturing process that will affect the opening and closing rate of the valve,” states Bechtloff. “The position on the rocker that you implement the pivot, where exactly the push rod makes contact, and the distance between the center of the fulcrum or trunnion and the end of the rocker will all have an effect on how quickly the valve snaps open and shut.”
As an example, say you have a rocker arm with a 1.7 ratio. With Quick-Lift, the valves will initially open with an increased ratio of 1.78, and then drop to a 1.7 ratio right around mid-lift, then snap shut again at an increased ratio. This quicker valve opening rate allows for more time for air to fill the cylinders, increasing power.