we get asked daily how to adjust our adjustable pushrods, so i figured i'd do a quick article on it. a lot of our customers are turned off by using them as they assume that adjusting them is going to be above their skill level. let me assure you, that if you've built your engine yourself up the this point, you arn't going to have any problems with this.
from the factory, all nailheads had hydraulic lifters/cam aside from extremely rare factory export kits. i've shared some factory paperwork describing what the early engine export kit came with, which includes high compression pistons, heater risor passage block off intake gaskets, and solid lifter cam with adjustable export rockers. you can check that out on my instagram. all stock hydraulic lifter valve trains were non adjustable from the factory.
do you need adjustable pushrods after a rebuild? the plus/minus absorbing tolerances of the hydraulic lifters is pretty forgiving. can you get by without them? yes but its not recommended. that being said, adjustable pushrods are a much better option. after a rebuild, you inevitably have a wide spectrum of variables that can effect lifter preload, such as camshaft base circle, head and block decking/surfacing, head gasket thickness, rebuilt or replaced rocker arms/tip thickness and valve stem install height. because of all that, adjustable pushrods that we sell (which are far stronger than stock ones) get used as standard practice on every engine we do regardless of the engine being otherwise stock. exceptions to the rule are if aftermarket adjustable rockers are used, outside of factory export, such as TA rollers. take note those rockers allow too much oil to the top end and are the only circumstance that seals should be ran on both the intake and exhaust as they flood the top end with oil. other aftermarket rockers that come to mind are rare thomas ones, gotha, and tolesco. the gotha ones are horrible and have poor oiling. when using aftermarket adjustable rockers, we have custom 3 piece pushrods made.
directions for install: place the adjustable part of the pushrod in the valley! much, much easier and less work to adjust the pushrods with the adjustments in the valley than try to access the adjustment right below rocker arms under the valve cover. with the lifter on the heal/base circle of the cam lobe, turn the pushrod out to zero lash (positive contact.) at that point, mark the top portion of the pushrod, right above the jam nut with a paint pen. now turn out the pushrod exactly one full turn past positive contact. thats .030". now just lock down the jam nut with THREE wrenches. do not use 2 wrenches or adjustment will continue to rotate while tightening down and preload measurement will no longer be accurate. do one pushrod at a time and go over each individual one again after youre done. even with zero experience, this preload adjusting process shouldn't take you longer than 20 minutes. always prime oil pump until oil gets to the rockers before firing an engine after lifter replacement/ engine assembly.