If its a clanking sound, it sounds like a rod. Lifters are more of a rattle. Does it sound like its coming from under the hood?
Also, I'm going to try to get a moderator to move this into the Tech forum. This forum (talk) is more for off topic stuff, kinda helps keep the tech forum cleaned up.
I'm going to move into tech. is the sound occuring at the same rate (RPM) as the engine, twice as fast? Thick metal to Thick metal? or tinny?is it just up hill or does it happen under other circumstances? Have you tried taking a long screwdriver to listen to exactly where in the engine the sound is comming from (becareful of the pullies and fan)?