pushrod length
First, bolt the heads down and fully compress the gasket by torquing to spec (if installing new heads). Take every variable out of the equation.
Put the rocker on just holding your finger and spin the adjustable pushrod until all the slack is taken out of the rocker. That means no up and down motion anymore. You’re at 0 lash. Some say to bolt down the rocker, but that’s has some movement and preloads the system and gives you a short pushrod. Just tight enough to remove the play is all you need. And you can do this with the performance valve springs installed. No need to run checker springs with this method.
Next take the adjustable pushrod out and count the number of turns back to 0. Half turns are important and are .025″ length. Multiply the turns by .050″ and add to the baseline 6.8″ and that’s your pushrod length at 0 lash. Add your preload to that. If LS7 lifters, aim for .050 to .075″ additional length.
You can check the pushrod length by spinning it out the original 0 lash number and then an additional half to 3/4 turn to build the proper length. Then bolt down your rocker (again just tight enough to get all slack out) and set your torque wrench to 22 ft-lbs. Measure the number of rotations to get to 22ft/lbs. You should be between a full turn and a full turn and a half depending on the .050 or .075″ preload number. If so, you’re good to go.
Check an exhaust and intake on both cylinder heads if you don’t want to check all 16. That way you can check both the intake and exhaust lobes and the variance from deck-to-deck.
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Mine were 7.400 but I know 2 others who ended up with 7.375 and 7.425.
Here is a vid that will help. 2010-01-09-LS3-Pushrod-Measurements - YouTube





