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 Prior to installation the valvesprings were checked to ensure that they were up to task of controlling valvetrain with our hydraulic roller cam. The valvesprings on the 6Xs measured 130 psi at the 1.685-inch installed height and 275 psi at 1.175 inches. The spring rate is 284 psi. On the E-heads they checked in at 110 psi at the 1.780-inch installed height and 275 psi at 1.210 inch. The spring rate is 289 psi. Shown here, the head bolts were torqued to 100 ft-lb in the proper sequence.