Here's the rocker arms. These are 1.6 ratio. the stock rockers are 1.5 ratio.

Remove the valve cover. These particular bolts use a 3/8 socket to remove.

With the valve covers off, now it's time to take the rockers off. You will need a 5/8" socket for this. The way to do this is one cylinder at a time in the firing order of 1-8-4-3-6-5-7-2. Put the #1 cylinder on the compression stroke by lining up the timing mark on 0*. Can verify you are on the compression stroke by removing the distributor cap and verifying the rotor is pointed at the #1 plug wire. Putting the cylinder on the compression stroke ensures the lifters are on the base circle of the cam. That way the lifter is at zero lift.

Here is a diagram of the cylinder location for a small block chevy.

Now be careful when removing the rockers. Don't want the pushrod to fall into the motor.

When upgrading to a larger ratio rocker, you will want to verify that the pushrods will not hit the slot in the head. The 1.6 ratio rockers bring the pushrod closer to the stud side of the slot.

This procedure to properly adjust rockers is for hydraulic cams. Either flat tappet or roller. Install the rockers onto the studs. Make sure the pushrod is in the socket in the rocker arm. Using a 5/8" wrench, tighten the posi-lock until there is no slack between the pushrod and rocker. I check by seeing if I can lift the rocker off the pushrod. Other way to do it is to turn the pushrod as you are tightening the posi-lock. Once you feel resistance. you are at zero lash. Meaning no slack between the pushrod and rocker. Now what I do is tighten the nut 1/4 turn. Then tighten the lock. Then, at the same time, I turn both another 1/4 turn. This way the lock is real tight. Don't want it to loosen up. Now to check the pushrod to slot clearance, turn the motor over 2 full turns. Watch for the pushrods to hit the slot edge closest to the stud. The reason you turn the crank 2 full revolutions, is to check for both pushrods on the cylinder and to bring you back to #1 compression. Most cams have more duration and lift on the exhaust side. So you want to make sure both pushrods clear the slot edges.

Once you have done the #1 cylinder, you turn the motor at the crank with a 5/8" socket clockwise 90*. This will put you to #8 compression stroke. Repeat the above procedures. Then turn the crank another 90*. Now you are at #4. Repeat the steps again. Keep going until you have done all eight cylinders.

Here they are all on the driver's side.

Now, the rockers do hit the centerbolt support when you go to put the covers back on. not all rockers will fit this easily. You will need to check clearances and make sure they fit without touching the supports. Crane Cams and Comp cams make rockers that will fit under the covers without modifications.

So, thinking it was the ends, I cut the tips off on each side like this. But, that was not where it is hitting. When you look at the roller rockers installed, there is little room between the trunion areas. When I put the covers back on, it still hit. What I did was finish pushing the valve cover past the rockers. Once I got it all the way down, it didn't hit the rockers. I started the car and no scraping noises.