i have a 2003 3500 that needs a overhead valve adjustment. How difficult is that to do. What are the steps to do this.

 

Michael has a good write up here

It is suggested to be done at 150K miles which I think is too far down the road. Mine where out of adjustment a bit at 92K miles. So this is how I did my valve adjustment on my truck. Valve adjustment is fairly simple to do and does require much for tools. You need a feeler gauge set (0.010 and 0.020), 9/16" box wrench, 10mm short socket, 15/16" socket, both 3/8" and 1/2" ratchets, Allen wrench and a mirror. The first thing you need to do is pull the valve cover off the engine. You'll need a 10mm short socket and a 3/8" ratchet. Loosen all the bolt till you can lift the bolt up. Don't bother removing the bolts from the valve cover. Once you got that the valve cover will come off on the passenger side. You got to slide it towards the turbo and work it over the top of the heater hose. Take your time is will go... Now you need to use your 1/2" ratchet and the 15/16" socket to rotate the alternator. You want to turn it towards the passenger side (or towards coolant bottle). You want to get the gear to be in the TDC (Top Dead Center) like in the picture above. Now you'll start adjusting valves. But you can adjust all of them right now. Intake valves 1, 2, 4 and Exhaust valves 1, 3, 5 which I've circled for you. Using a feeler gauge you want to adjust all intake valves to 0.010" gap and all exhaust valves to 0.020" gap. You'll be inserting the feeler gauge like shown. This is the part you got to take your time on. As you'll notice as you tighten up your adjustment screw the feeler gauges seems to be pinched in-between but try to hold the feeler gauge flat you'll notice it get loose again. So take your time... Now when you get ready to tighten the lock nut finger spin it tight. Then as you tighten the nut you go to hold the adjustment screw still. But if you notice your gap is loose twist both nut and screw tighten a little bit. Or twist the adjustment screw loosen as you tighten the nut. This will increase or decrease the gap a little but not much. Now that you done this set now you go to do the other half of the valves. So now twist the alternator some more till you see (BDC -Bottom Dead Center) for the VP44 pump gear. Now adjust the the rest of the valves. Intakes 3, 5, 6 and Exhaust 2, 4, 6. They are marked in the picture below. Double check all the jam nuts that they are TIGHT! You now have completed a valve adjustment on you engine. Now you got to reassemble the valve cover. Replace the gasket if it damaged. Then remount the breather cover on the gear case and hook up the vent tube. You'll hear a slight difference when you start the truck up. It going to be a bit quieter. Let it idle a bit and double check your valve cover for leaks. For whole write up it here... Valve Adjustment

 

B Series Valve Adjustment
hope this helps you