I recently had to remove my gearbox to cure a gear selection problem which turned out to be a bent clutch fork, it had actually bent so much it had split and and was fouling the clutch pressure plate. Anyway after getting everything back together the car refused to start. It had probably been stood for 2 weeks due to not been in any rush to fix it and the battery had gone flat. I charged the battery and it would crank and crank but not fire. It was getting fuel and a spark but refusing to fire but what I did notice was it sounded low on compression so I checked the cam timing and all was fine. Eventually after lots and lots of cranking it started trying to fire on the odd cylinder so I persisted and it fired up and ran but was struggling to idle, after a couple of minutes it idled and ran perfectly and now fires up spot on every time. Now the problem I have is sometimes the top end starts rattling/tapping from under the valve cover, sometimes it goes away when I rev it but sometimes gets louder if I rev it, there's no real consistency to it. In some cases I can drive it without it rattling at all. The really strange part is if I'm driving along and it starts making a noise, if I turn the engine off and back on it goes away guaranteed everytime and may not come back for 10-15 mins. So what I'm wondering is could all that cranking have caused top end damage due to not enough oil pressure ? Or could it be that because the car was stood still for 2 weeks (usually used daily) and all the oil might have drained out of the cam chain tensioner and now it's struggling to pump back up properly ? If the cam chain tensioner had gone really soft could that have explained to seemingly low compression when cranking ? Or could I have a blocked oil pickup pipe /failing oil pump starving the top end of oil ? It's just very strange how it's not consistent and turning the engine off and back on makes the noise go away for quite a while. Sorry for the long post but I wanted to be detailed about what has been happening. Any advice/info would be greatly appreciated. Regards, Ben.