Here is what I do.  Set motor to TDC on the power stroke of no 1 cylinder
(this is the cylinder closest to the front of the van on the passenger side).
Take off the rotor cap and make sure the rotor is pointing to this cylinder's
tower so you know you are on the power stroke.  Now you adjust the valve
adjustment screws in while twisting the push rod between your fingers a
little.  When you just can't turn the push rod with the tips of your fingers
then stop.  After you have adjusted both valves like this on Number 1 then go
180 degrees to opposite cylinder (number 4 I think).  Now adjust these valves
and then turn the thing 90 degrees adjust that cylinder (number 2) and then
180 again and adjust that cylinder's valves (number 3).  OK now that you have
them all even (if you couldn't adjust some of them at all then you have not
centered the pushrods in the lifters correctly) now go back to no 1 and set it
back to TDC on power stroke.  Tighten the screws two half turns (180 and 180).
Now go back through all the other cylinders and adjust them as well in the
same order that you did before.
I have done this several times and always with excellent results.  Most of the
time any problems I have had doing this comes from the pushrods not being
centered properly so please becareful of that.
Have fun.
Ken Wilford
Van-Again
John 3:16