Setting Valve Clearance using Vacuum Gauge

I have heard of people setting lash on solid lifter \6's with the engine running and I have even tried it but it beats the snot out of your feeler gauges and and as moper has stated it's tough on your hands. I found by doing it I wound up with to tight a setting.

The referenced article by PRO sound like he was doing it on a hydraulic cam. If you are in the operating stroke of the the lifter I can't see how you could influence the manifold vacuum at all. There may be a momentary change until the lifter either pumps up or bleeds down but once it stabalizes there should be no difference.

Typically you get higher manifold vacuum with less valve over lap. If you use that technique I would expect that you would wind up with very loose valave lash (more lash = less duration = less overlap).