803cc timing chain

[trabant]

My everyday series 11 has developed what seems to be timing chain rattle I believe this is fairly common ? Anyway the manual I have is for the 948 & 1098 and I'm wondering how the 803 Timing.chain is tensioned I already know I'm.going to have to change the lot don't panic.

[trabant]

As an add on to that what do I actually order as in what will fit without changing the timing chain cover etc.

[philthehill]

The timing chain is tensioned exactly the same way as the 948cc and 1098cc in that the chain is tensioned by the rubber rings.
You can fit a simplex or a duplex system without changing the timing cover.
Fitting the duplex to me is a no brainer as it has the potential to last considerably longer than a simplex.
Better if you do change the timing cover to one with the lip seal as the old felt seal is very inefficient in retaining oil to within the timing cover. Good when new but soon looses it efficiency.
See my posts of the 27th / 28th Jan regarding timing chains/sprockets etc.

http://www.mmoc.org.uk/viewtopic.php?f=4&t=62758

Phil

[trabant]

Thanks very much its actually how the two rubber rings do the tensioning that bewilders me somewhat .

[philthehill]

The outer diameter of the fitted rubber ring is larger than the running diameter of the chain when passing around the cam sprocket therefore the chain when fitted compresses the rubber ring and so puts tension into the chain.
Unfortunately the rubber rings soon loose their tensioning ability and you are back to a rattily chain in a very short time.
Phil

[trabant]

Concept grasped that does seem a somewhat daft way of doing it good old BMC.

[philthehill]

Cheaper than using intermeshing gears.

[ManyMinors]

And, to be fair, plenty of them have lasted more than 40years without giving any trouble at all - not bad for a car which was cheap even when new .
Compare that with my expensively built modern car which requires a new cambelt every few years at rather greater cost!