I've seen a lot of threads lately from guys wondering how to properly adjust valves and set lifter pre-load with adjustable-type rocker arms, so here it is. This will explain how to properly set lifter pre-load with stud-mounted rocker arms; stock, pedestal-mount rockers will generally not need to be adjusted unless you have installed a reduced base circle camshaft.
Glossary:
Adjuster Nut: The tall nut that threads onto the rocker arm stud and sets the lifter pre-load. Usually a 5/8" hex nut.
Set Screw: The allen-head screw that threads into the top of the adjuster nut. Usually takes a 3/16" bit.
Zero Lash: Where there is neither play in the rocker arm or pre-load on the lifter.
This method is generally known as the exhaust-open, intake-close method.
1) Before you start, you'll probably want to remove the fan and fan shroud so that the motor can be rotated with a socket on the harmonic balancer bolt. The stock balancer bolt will require a 15/16", six-point socket, most aftermarket bolts use a 5/8", 12-point socket.
2) With the valve covers removed, choose the cylinder that you will adjust the valves on first. I like to start with the #1 cylinder, then do #2, #3, etc. While it is possible to jump around between cylinders and maybe save some time, going 1,2,3... ensures that you won't miss any valves.
3) With the socket and a breaker bar (or ratchet, whatever), rotate the engine until the exhaust valve on the #1 cylinder just begins to open. At this point, the #1 intake valve is fully closed and the intake valve can now be adjusted.
4) Loosen the adjuster nut and the set screw, backing the adjuster nut off several turns. Wait about 30 seconds to let the lifter pump back up; even though there is no oil pressure in the motor, the lifter contains a spring that will push the pushrod seat back up against its retainer clip.
5) Now comes the part where this gets a little harder. You need to tighten the adjuster nut down onto the rocker arm until the rocker arm is at zero lash. Most procedures tell you to spin the pushrod with your fingers until it no longer wants to turn freely, but, in addition to the pushrod being difficult to grasp with the intake manifold installed, it is possible with modern, super slick synthetic oils to adjust the rocker arm well past zero lash before and resistance is felt on the pushrod. Therefore, the method I suggest is to simply wiggle the rocker arm back and forth gently (in the same manner as it opens and closes) until there is no play in it. You want to use a wrench on the adjuster nut at this point, just tightening it finger-tight will do.
6) Once the adjuster nut is at zero lash, tighten the set screw in the middle of it down unitl it just comes into contact with the top of the rocker arm stud, then back it off about 3/16 of a turn. Now, tighten the adjuster nut down tightly (to about 30ft/lbs of torque). This torque spec should have turned the adjuster nut about 1/2 turn past where it was at zero lash. This is generally referred to as '1/2 turn of preload'. If it turned less than 1/2 turn but more than a 1/4 turn, then you're fine. If it turned more than 1/2 turn, back the adjuster nut off and repeat this step (#6), but, this time, back the set screw off a bit less than 3/16 turn. This part is something you'll just need to get a feel for on your particular motor, but, after you find how much you need to back the set screw out, that amount will work for the rest of the valves.
7) Once you have the intake valve set at 1/4 to 1/2 turn of preload, it's time to move on to the exhaust valve for the #1 cylinder. To get make sure that the exhaust valve is fully closed, rotate the engine with your breaker bar until the #1 intake valve (the one you just adjusted) opens fully and begins to close again. When the intake valve is almost fully closed, repeat steps 4,5, and 6 for the exhaust valve, remembering to back the set screw off to the amount that you determined while adjusting the intake valve.
8) Turn the engine over until the exhaust valve for the #2 cylinder begins to open, then adjust it as you did the #1. Continue until all the valves are adjusted, and remember to adjust them in order so as not to lose track of which ones have been adjusted.
Hope this helps.
Brian,
Glossary:
Adjuster Nut: The tall nut that threads onto the rocker arm stud and sets the lifter pre-load. Usually a 5/8" hex nut.
Set Screw: The allen-head screw that threads into the top of the adjuster nut. Usually takes a 3/16" bit.
Zero Lash: Where there is neither play in the rocker arm or pre-load on the lifter.
This method is generally known as the exhaust-open, intake-close method.
1) Before you start, you'll probably want to remove the fan and fan shroud so that the motor can be rotated with a socket on the harmonic balancer bolt. The stock balancer bolt will require a 15/16", six-point socket, most aftermarket bolts use a 5/8", 12-point socket.
2) With the valve covers removed, choose the cylinder that you will adjust the valves on first. I like to start with the #1 cylinder, then do #2, #3, etc. While it is possible to jump around between cylinders and maybe save some time, going 1,2,3... ensures that you won't miss any valves.
3) With the socket and a breaker bar (or ratchet, whatever), rotate the engine until the exhaust valve on the #1 cylinder just begins to open. At this point, the #1 intake valve is fully closed and the intake valve can now be adjusted.
4) Loosen the adjuster nut and the set screw, backing the adjuster nut off several turns. Wait about 30 seconds to let the lifter pump back up; even though there is no oil pressure in the motor, the lifter contains a spring that will push the pushrod seat back up against its retainer clip.
5) Now comes the part where this gets a little harder. You need to tighten the adjuster nut down onto the rocker arm until the rocker arm is at zero lash. Most procedures tell you to spin the pushrod with your fingers until it no longer wants to turn freely, but, in addition to the pushrod being difficult to grasp with the intake manifold installed, it is possible with modern, super slick synthetic oils to adjust the rocker arm well past zero lash before and resistance is felt on the pushrod. Therefore, the method I suggest is to simply wiggle the rocker arm back and forth gently (in the same manner as it opens and closes) until there is no play in it. You want to use a wrench on the adjuster nut at this point, just tightening it finger-tight will do.
6) Once the adjuster nut is at zero lash, tighten the set screw in the middle of it down unitl it just comes into contact with the top of the rocker arm stud, then back it off about 3/16 of a turn. Now, tighten the adjuster nut down tightly (to about 30ft/lbs of torque). This torque spec should have turned the adjuster nut about 1/2 turn past where it was at zero lash. This is generally referred to as '1/2 turn of preload'. If it turned less than 1/2 turn but more than a 1/4 turn, then you're fine. If it turned more than 1/2 turn, back the adjuster nut off and repeat this step (#6), but, this time, back the set screw off a bit less than 3/16 turn. This part is something you'll just need to get a feel for on your particular motor, but, after you find how much you need to back the set screw out, that amount will work for the rest of the valves.
7) Once you have the intake valve set at 1/4 to 1/2 turn of preload, it's time to move on to the exhaust valve for the #1 cylinder. To get make sure that the exhaust valve is fully closed, rotate the engine with your breaker bar until the #1 intake valve (the one you just adjusted) opens fully and begins to close again. When the intake valve is almost fully closed, repeat steps 4,5, and 6 for the exhaust valve, remembering to back the set screw off to the amount that you determined while adjusting the intake valve.
8) Turn the engine over until the exhaust valve for the #2 cylinder begins to open, then adjust it as you did the #1. Continue until all the valves are adjusted, and remember to adjust them in order so as not to lose track of which ones have been adjusted.
Hope this helps.
Brian,
