Can’t budge two top chain guide Allen bolts S38B35

[Syndrome]

Hey all. I’m getting down to brass tacks on my engine and am working to get the head dismantled, thanks to your help. I have a little problem, which is a bit frustrating. There’s are two Allen bolts that hold the top chain rail/guide in place. I have to remove these to get the head off, but they are really ornery. I can’t get them to budge and they’re starting to feel like they’re about to strip (the hex socket is beginning to round out). What’s the trick to this??? Seems silly, but wow, these are not moving. Please help. Thank you.

[Fanclutchnut]

Maybe impact driver? The kind you put the socket on and hit with a hammer.