What's the problem, though? If it's not squirting out water, and temps are in the 215* range, then you should be OK.
If you have aluminum heads, they transfer heat faster than the cast block. I wouldn't be surprised if they run a little hotter than the rest of the system, but what do I know, I have cast heads.
If you are squirting out water , then that's another problem, but that might be a euro filler neck with a USA cap.
Good luck =