Hydraulic lifters Stuck? Bad?

[dom14]

Hey Guys,

I'm wandering whether the hydraulic lifters stuck like this(not moving at all) indicates they are bad beyond any use. Out of 12 lifters in this cylinder head(RB30 Nissan), only two moves. That's why I am not sure whether they are actually bad or may be in a stuck position due to some reason, but not necessarily bad??!!!

https://www.youtube.com/watch?v=5V_V...ature=youtu.be

I know if I blow a bit of compressed air into a lifter through the oil receiving hole, it get momentarily stuck.
But, I did no such thing with these lifters. They belong to the original old cylinder head that came with my RB30.
I have another cylinder head which goes onto the engine block today has only two stuck lifters like this.
My idea is to swap two from the old one, and funnily enough only two moving lifters that I can see on the old cylinder head.

Any of your opinions, explanations will be appreciated.

Thanx in advance.

Dom

P.S. The cylinder head, rockers, lifters, etc are pretty clean looking 'cos it runs on LPG all the time. So, I don't think it's carbon build up, but not all that sure. However water got into oil by blown head gasket, so I don't know whether the water-oil mixture can stuff up the lifters like this.