Hey Guys, I've noticed lately that sometimes I get a loud valve clatter when pulling mild slopes at 55 mph. I've toyed around with diff. octanes, and don't seem to notice a correlation between reg-unleaded, super, and the mid-range stuff. I'll drive the same section of freeway, and sometimes it'll sound like a damn diesel, other times, it'll purr like a kitten. The engine is the original 305 with 106K miles. From what I've been reading, I'm hoping like hell to get a good 180-200K miles before having to drop a new engine in. Could this just be an indicator of the need for a tune-up? Also, I hear a noticeable tick (lifter noise?) at warm up; about 100 degrees F on the coolant gauge. Noise lasts for a few seconds, but then goes away. As you can tell, I'm not the most adept backyard mechanic. Could the two be related? Love any input.