I'm going to answer your questions backwards! It will make more sense when you go to do the job. First off, DON'T mess with the valve adjusters when taking the engine apart. Remove the bolts that hold the rocker shaft to the cylinder head. Assemble in reverse order, go very slow as you tighten them down so you aren't twisting the rocker shaft and carefully watch the push rods to make sure they come in contact with the rockers properly. Your clearance should already be pretty close so you will just have to bring the adjustment to spec. There is more than one (correct) way to adjust valves but I'm going to stick with one that is easy to explain and applicable to your repair.
"Do you use a a wrench on the front of the engine to turn it for each adjustment?"
Yes, put a wrench on the harmonic balancer and turn clockwise as if you were tightening the bolt. Remove the spark plugs so it's easy to turn.
How do you know when the 1st cylinder or any cylinder is at top dead center?
Number 1 should be at TDC when the timing mark aligns with 0 degrees and the distributor rotor is pointing to the number one position on the distributor cap. Mark the distributor body by the number 1 plug wire, then when you take the cap off you can still see where number 1 was. You can confirm you're in the right place by checking the rocker arms. Number 1 intake and exhaust rockers should both feel loose. This is the valve lash that you will be adjusting.
I am wondering about how to adjust the valves on this old motor once the head is back on.
The service manual suggests that you make 2 additional marks on the harmonic balancer, 120 degrees apart from the #1 TDC mark. Once done you should have 3 evenly spaced marks around the circumference of the damper. Start with #1, bring to TDC, both valves should have some play, adjust so that a .019" feeler gauge fits in between the end of the rocker arm and top of the valve stem. Intake and exhaust are both .019". Once complete, turn the crankshaft 1/3 of a revolution (to the next mark) and repeat the process for #5. Repeat this same process for every cylinder by firing order which is 1-5-3-6-2-4. When you get to #6 you should be back on the same mark as you started with for #1 but the rotor should be pointing 180 degrees in the wrong direction from #1. If so, that's correct. Keep going until you've completed #4, then you should be finished.
You should adjust the valves cold (before you start the engine after the repair). The service manual also recommends you adjust them hot after it's running. If I were doing this to my truck I would adjust the valves cold; complete assembly; change the oil before starting; start the engine and let it fully warm up; change the oil and filter; drive it some (put about 3-4 hours on the engine); re-torque the head gasket (cold); and re-check the valves (hot). You will probably not have to adjust very much the second time. If you have to err on the valve adjustment, it's better to be a little wide than too tight.
Good luck with it!
Lou
