COMP Cams offers its Pro Magnum roller rocker arms for small-block Chevys in both 1.5 and 1.6 ratios. Previously, we had found the most average power using 1.6 rockers on all valves. This month we tried 1.5's on the exhaust only and got little in return.
Our main goal for this whole test was never realized. We wanted to run COMP's 1.3:1 (PN 1012-16) special break-in rockers on the exhaust to see if the reduction in lift would make more power as some claimed. But, in order to decrease the ratio, the rocker arm's pushrod cup must be moved away from the trunion centerline. This in effect caused the pushrod to hit the cylinder head (note top of pushrod in photo). Had we not checked for this interference and ran the motor, power would have been down tremendously and damage could have resulted. Always check for proper pushrod clearance when installing new rocker arms or changing ratios.
Test: 25 Swapped COMP Cams 1.5:1 Pro Magnum roller rockers on exhaust only
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