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#6---Rocker Arm Ratios

11/24/2025 Dave Hughes

#6 Rocker Arm Ratios Rocker arms have a ratio, for example 1.5:1. That means that if the pushrod end moves one unit (example :.001”), the valve end will move 1.5 times that amount (.0015”). However, note that the adjusting screw is at an angle to the valve stem, when the rocker ‘s mounted on the cylinder head. This means that the adjusting screw’s length out of the rocker body will affect the ratio. This is not a big deal with 1.5:1 rocker arms with cams with about .450” to .500” lift. However, with high ratio rockers (1.6:1 or 1.7:1, etc.), it can make a considerable difference. Enough to make you think you got the wrong rockers, or camshaft. Our rockers are checked with a custom gauge that sets the adjusting screw ball to a predetermined position to check the ratio; and, if you use an off-set rocker where the adjusting screw is not in line with the valve stem, the problem gets worse very quickly! We have some custom-made gauges that set the adjusting screw (ball) position. At a predetermined distance, the gauge positions the adjusting screw with approximately two threads exposed between the adjusting ball and the rocker. This can be difficult to check in the field, as the threads are not exactly the same on every adjusting screw. We have had customers try to measure the ball position and claim the rocker ratios are incorrect. However, when checked with our gauge, they are correct. We check all shipments of rockers when they arrive to make sure they are correct before we put them in stock.