WHOOPS!!
Increased ign advance a few deg and vvt upto 290 at full throttle 6000rpm onwards.
No problems, fractional pinking from idle too pulling away with light throttle(expected).
Zoooming around no worries; temp below 90deg, head into town, stop for sandwich and fuel (10min stop), pull out of garage into high street conditions ie cruising in 2nd light load and rpm (no pinking).
After 5-10minutes in 3rd light load low rpm, nasty ticky/clunk noises, suspected dropped valve or something clanking around in chamber.
Removed rocker cover, plugs looked fine and equal, turned engine over with socket, inlet cam â??snappingâ?� on 2 followers, then (this is weird) the cam lobs in question (2 of them ie 1 cylinder) stopped rotating completely despite the next cam still rotating (the same end pair!).
Thought something broken in VVC mech unit. Removed to discover everything fine and in place. Looking at the ends of the 2 cams couldnâ??t see how 1 might rotate independently of the other. Unless the cam flanges are friction fitted????
Closer inspection shows the same respective cylinder tappets lower in head (50thou clearance to cam lobes). Suspect equally bent pair of inlet valves.
My assumption is this:
VVC mech locks up internally, piston valve contact, cam slips/freeâ??s up on cam flange as a consequence.
Or
Cam flange slips/freeâ??s up on cam, valve piston contact, cam snaps at low follower, gives up completely once rotated by hand.
(if it were a sticking valve then only 1 would be bent and only 1 follower low).
Thereâ??s no debris or wear marks anywhere, although the inlet cams in question feel awkward to rotate.
If it was a VVC mech lockup why did this arise when at low cam duration.
Anyway, head off time and the opportunity to upgrade exhaust cam and ceramic coat chambers to prepare for turbo.
