WARNING! This procedure must be done with a cold engine. Engine coolant should be below 140°F.
I set my valves today, figured I would show everyone how I do it. As long as you know the firing order and valve lash (which are both on the cummins id tag) you can set the valves.
This is called the valve overlap method. Basically the pistons have running mates. Running mates are pistons that go up and down together in exactly the same positions, as in they both hit TDC at the same time. The difference is that one of them is on the compression or power stroke, and the other is on the intake or exhaust stroke.
To find the running mate, you simply take the firing order and split it in half. Our cummins' firing order is 153624. So splitting it in half would mean 153-624. If you put the second number under the first, you would have 1/6 5/2 3/4 So 1 is 6's running mate and 5 is 2's, 3 is 4's.
Since the running mates are 360 degrees out of phase, when one of the hits TDC compression/power stroke, the other is hitting TDC exhaust/intake stroke. This is perfect for setting valves because you can simply watch the running mate of one piston and it will be on the exhaust stroke with the exhaust valve open, when it hits TDC and transitions to the intake stroke, the intake valve will open. Once you see that intake valve move, stop. This is TDC, or as close to TDC as we need to be. The running mate will be on the very end of the compression stroke and the start of the power stroke and the valves will be on the opposite side of the cam lobe since they must be shut during the compression and power strokes. You can now adjust the running mates valves, intake and exhaust.
For example. To do the valves on #1, you would watch #6. The #6 will open and close the exhaust valve and once the exhaust valve closes and the intake starts to open, you stop and now you know it is at TDC. Since 1 is it's running mate, you know 1 is on TDC compression/power so you can do both valves on #1.
Now look down the line and you will see that the exhaust valve on #2 will be open. Since 5 is after 1 in the firing order, 5 will be the next valves you adjust, and since you watch 2 because it is 5's running mate, you will watch #2's exhaust valve close and start to open the intake, you stop and do the valve on number 5.
Basically you will be turning the engine 120* to do each valve. You will do them in the same order as the firing order.
Here is the reference order. Do 1 by watching the valves on 6. Then 5 by watching 2. Then 3 by watching 4. Then 6 by watching 1. Then 2 by watching 5. Then 4 by watching 3.
The next one you watch will have the exhaust valve open so that will be a clue that you are doing it in the right order. It is a very fast and bulletproof way of doing it. It works on any engine also. Just split the firing order and stack them and you have your running mates like I showed earlier, it always works.