Before we all start stripping engines down and rebuilding, a look under the rocker covers for a broken tappet or rocker would be the cheapest and first check. Don't be too quick to start calling slipped liners without ruling everything else out first..Pretty sure that sounds very different, cheers for the link! Yes it does go away, I'll have to record it again and this time rev it, it seems easier to hear played back than over all the engine noise