Stevie lowers our Pony’s stroked motivator between the fenders. Why is the exhaust valve for the No. 4 cylinder exposed? Plain and simple, we misplaced one of the retainer nuts for the rocker arm and simply moved forward with the installation until a suitable replacement was found. Notice that the Cobra rockers are standard bolt-down pieces that use the factory mounting channels. While stud-mount rockers are a more rugged option, going that route requires additional machine work on the iron cylinder heads, which can be expensive. By going with the 1.7-ratio rockers, valve lift for our setup increases to 0.544/0.544, which is still within the safe parameter for piston-to-valve clearance.