The amount of load a spring delivers is as much a function of its designed spring rate as its installed height. When ordering springs, a measurement of the available installed height is a key piece of information in selecting the proper springs. These Mopar big-block heads had 2.060-inch installed height. With the required spring cup, the installed height will be 2.00 inches. Simply ordering and installing a spring designed for a Chrysler big-block, which typically has an installed height of 1.880 inches will result in way too little seat load. A COMP PN 924 spring for a big-block Mopar delivers 125 lbs load at 1.880 inches, while at 2.000 inches, the load drops to 87 lbs, too weak for even a stock cam. Measuring and noting the installed height is the only way to determine if a spring will deliver the load required. Powerhouse has these handy height micrometers (PN POW101200), which make measuring installed height a breeze.