![]() ![]() Here’s an excerpt from that older series and it still holds true today: “Typically, the drill (valve lash) went like this: First you loosen the stud girdle, and then you lash the valves. There was also a bit more to the equation: Replacing a conventional rocker setup/stud girdle combination saves a lot of work when you’re performing simple maintenance such as lashing the valves. Over the decades, that line of thinking expanded to function on all sorts of engines and all sorts of cylinder heads. The shaft rocker system wasn’t bound by the rocker stud location on the cylinder head, and it allowed Dan Jesel to move the rocker in a position on the head where it wasn’t scrubbing. But when you increase the lift dramatically (as seen in today’s race engines) and simultaneously increase the spring pressure you’re soon faced with another quandary: An increase in friction.”Įssentially, the new Jesel shaft rockers were a means to improve upon the rocker geometry of a small block Chevy. This isn’t much of an issue at lower gross valve lifts such as those experienced with stock or mild camshafts (such as those used in production engines). ![]() What this all means is the stock small block rocker arm tip more or less scrubs across the tip of the valve as it opens. In comparison, a big block has a pivot length of 1.65-inches). This means the arc it travels in is comparatively small, particularly in contrast to other pushrod engines (Jesel notes that a stock small block Chevy has a rocker pivot length of 1.45-inches. In that series we mentioned how Dan Jesel ( pretty much invented the new breed of rockers: “In something like a small block Chevy application, the stock rocker has a relatively short pivot length. ![]() That series explained why and how shaft work rockers work so well in race (and street-strip) applications. Roughly five years ago, we ran a series on shaft rockers. ![]()
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