I have a 1965, 200cid motor in my 62 comet. I just rebuilt it with new pistons, cam, lifters, etc...
I have it running but I have an issue with it. With it running I try to adjust valves. Zero lash plus 1/2 turn my vacuum gauge starts dancing and the engine runs poorly.. I tried setting int. and exh. to .016 and the vac gauge indicates 19-20 in vac. I took out old hyd lifters so I installed new hyd. lifters. While the motor was apart I had the block hot tanked and all oil galleys were checked. At first I thought I might not be waiting long enough for the lifters to bleed down but waiting made no diff. With the engine off I turned the engine over and adjusted valves one by one per the motor manual. When I started the motor, it ran really bad until I loosened all of the rockers again. I bought "Melling" lifters, and oil pump, and I primed them prior to installation. Oil npressure is steady at 55-60 lbs at idle. This isn't a performance motor, its just going to be a cruiser. Does anybody have any ideas other then adjust it as if I had soild lifters and leave it alone.
Thanks
Arnie
Valve Adjustment
Re: Valve Adjustment
forget the 1/2 turn,while ideling back off,til rattle then slowly tighten til rattle is gone and stop ! another way,,,motor not running,,,bar eng over til both valves are closed,spin push rod between finger tips while tight'n when you can't spin push rod any more,stop ,back off til you can ,do both same way then bar eng over til the next cyl has both valves closed and do the same,try to put same drag(spin) on each push rod the same,,,I like to adj mine to just a tick on the loose side ,gives a little more low gear torque and is not as apt to burn a valve,,,,this way works for me 
good luck 
pop
good luck pop