How do I know if my guinea pig likes be petted there ...?

  I have 2 guineas and both of them dont do much when i pet them they just sit there. Right now ive been petting one of them on the head n its starting to kind of lift its head up while im doing it. He will lift it up then put it down .. i dont know what this means & sometimes when im petting him on his head i can feel him grinding his teeth it feels like .. im not sure. Help?
When a guinea pig lifts his head up to your hand that is the ultimate of saying "wow do i like that" In fact that is what an exotic vet will do when a guinea pig looks a bit nervous, They will pet them on the head with a firm hand and the guinea pig will always respond by pushing back into their hand.That tooth grinding really does not mean any thing other than the guinea pig decided to chew on the food that he has hidden in his checks to chew on later and because you are touching him you of course can feel it.
My little guy lifts his head when patted and moves around and snuggles into me. Also he sometimes purrs and talks to me. I have a video of him talking to me and purring while I'm holding him around, but can't link it as it's on FB. So if he's doing any of that, I'd say you have a yes there.:)
One of the only place a guinea pig likes to be pet is on the top of their head. When they lift their head up and down, they are enjoying it. pets question and answers,www.5d2d.com



Guinea pigs grind their teeth often, so don't worry about it.:)
Maybe the grinding is him doing some sort of purring. I think that he likes it. It's nothing to worry about.