Hi all, i have two noises coming from the back, and my mechanic hasn't been able to track them down. firstly though, I just had an engine rebuild, full box and dice, about 500 k ago. first noise is a tapping sound seems to be on drivers side of motor. I asked what clearances were set, he said "hard 7" which is too much I think, so my question is would this cause the tapping. The tapping is worse in the morning, very cold here, and gets less obvious when the motor is hot, and goes away when the revs go past about half way. Should I get the clearances down to 5.5 or 6 thou and would it make a difference? second noise is maybe worse, I drove into Melbourne and back yesterday, 100 km round trip. On the way home and going up the escarpment towards Bendigo I hear this sound, sort of crackling noise or like sand flicking up against glass. Even maybe a bit like a crackling grass fire. I heard this before the rebuild and like this time it came with a loss of power, as I had to drop gear on a hill, that doesn't usually happen. I think this might be about the motor overheating. I had been cruising along at about 110 for 10 minutes or so, and the air coming through the heater was pretty hot. anybody got any insights? dennis P.S. - Just took it to the mechanic who reckons this crackly noise is probably pre-ignition. This would explain also the new oil leaks if the engine was overheated - the leaks are from the rocker cover and might have been due to overpressure.