Remembering why I
dislike working on
AO Silver Member
Join Date: Sep 2001
Sounds pretty normal TBH. You will always see some variation in tension as the engine moves round the cycle simply because at hand-turn speeds, the way the cams are pulled then pushed by the valve springs is very susceptible to where you happen to stop while turning, how well lubricated one follower may be, how freely it moves on that occasion, all sorts of stuff. If you looked at it with the engine running you would still see it 'chatter' but at a much higher frequency of course, so it looks less dramatic.
The point at which you set tension is the only 'defined' one, so as long as it is more or less right, most of the time, at TDC, and only if you stop at the right spot rotating the correct way (i.e. don't back up to it) then all is well. Other engines use different methods to try and avoid this problem I think. The MX5 engine for example has different positions for timing & tensioning.
A wee bit tight is OK, not too tight though - the tensioner needs to accomodate quite a bit of block and head expansion, so it's gets tighter as it hots up, using up that 'tight-side' adjustment space. On the old 12V motor they actually call the hydraulic one a de-tensioner.
A pointer thickness or so of variation is fine. Much more than that, think about adjusting it a gnats.
All IMO. YMMV!