Hi

I think you will find these have a hydraulic lifter below the push rod, so do not have a running clearance.

There is a method for the initial setting, but can't remember exact detail. AD help line gave me the info at the time.

Any other running issues ? restricted exhaust will also give low VAC. I have a feeling that these may have lower than normal idle vac, but yours look well down. Hopfully somone will confirm

Cheers Aidan