Turn the engine over by hand in the normal direction of rotation until the #1 piston is coming up on compression stroke. You can tell if it is compression stroke because neither rocker arm will be trying to open a valve as the piston is coming up. If it was on the wrong stroke, the exhaust valve would be trying to open. Continue to turn the engine until the piston is all the way up. Exact TDC is not necessary. Adjust the intake clearance to .010 inch and the exhaust to .012 inch. Some people prefer to remove the injectors so they can tell when the piston is up. An easier way is to watch when the intake valve closes completely, and then turn the engine another one half turn. There is a way that all the rocker arms can be adjusted by turning the engine to just 2 positions, but for accuracy I prefer to set them with the piston of each cylinder up on compression stroke which requires turning the engine to a different position for each cylinder. After adjusting #1, follow the same procedure for each cylinder, adjusting the valves when that particular piston is up on compression stroke. Like I said, exact TDC is not necessary, just so the piston is up. Having the piston up on compression stroke positions the camshaft so that your adjustments will be the most accurate. Hope I have not made this more confusing.