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Re: what are the symptoms of a worn timing chain Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Fri, 11 Feb 2005 06:24:17
In Reply to: what are the symptoms of a worn timing chain, kenS  [Profile/Gallery]
, Thu, 10 Feb 2005 22:01:19
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If a timing chain is badly worn, the valve timing will be a little off, probably not enough to notice engine issues. There are two possible issues with a really worn chain. The first is that since it's really long, and the tensioner fully extended, tension would be off, and it would be possible for the chain to jump a tooth on the cam or drive sprocket. The engine would run very poorly then. The bigger downside is that a worn chain is more likely to break. That would result in an engine that just stops, usually with major piston and valve damage. Not a good thing.
The first thing I'd do is check the flywheel alignment. Remove the spark plugs (make sure nothing falls in), and put a stiff wire into cylinder #1, touching the top of the cylinder. I like using the rod end of a vernier caliper. Turn the engine until the piston in cylinder #1 comes to the very top, and compare that to the flywheel marking. The flywheel marking is nice, but TDC is all about the piston.
At TDC, the alignment marks should line up properly. There is a little "V" there - the marks on the exact center is excellent, but if the line is within the width of the arms of the "V", that's acceptable.
If you simply set the mark on one cam to the line, the other one will almost assuredly line up, unless you've jumped a tooth. That's only measuring the stretch in the chain between the two cams - only a few inches. The distance from the crankshaft sprocket to the cam is a lot longer, and a much better measurement of chain stretch.
I don't expect the flywheel mark to be off from the cylinder TDC, but it's and easy test to be sure.
posted by 192.249....
, Thu, 10 Feb 2005 22:01:19, Fri, 11 Feb 2005 06:24:17 <-- Viewing This Message
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