Been reading through this thread, and it reminded me of something that happened many years ago.

Then, I had a Toyota Celica 2000GT. with a chain-driven DOHC engine....

During the usual servicing I did normally monthly, I noticed the Ignition timing retarded over two months tests. I re-set and basically forgot about it...

Then I had a rattling/knocking, just like pinging noise. A few days later, the lower crank chain sprocket broke....

The central bolt holding the crank pulley and crank-sprocket had worked loose and the sprocket wore the key in the crank and eventually broke, leading to 3 bent valves and a couple of broken guides...

The point to the story, was that when checking the timing, it was varying wildly over a short space of time due to the wear accumulating at the crank sprocket/Woodruff key in the crank....

I hear quite a few 'new' engines here in the UK with cam-belts suffer from this very problem too...

Definately worth checking that central bolt in the crank that it is fully tight, Just in case.....

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Alastair AKA H.C.II South Wales, U.K. based member

W123, 1985 300TD Wagon, 256K,
-Most recent M.B. purchase, Cost-a-plenty, Gulps BioDiesel extravagantly, and I love it like an old dog.

W114, 1975 280E Custard Yellow,
-Great above decks needs chassis welding--Really will do it this year....