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Gday , I've just got a little puzzle for people to have a think about. After fitting a timing chain on an engine and lining up the timing marks it appears the cam timing is half a tooth out.What might be wrong? I've put this question to a few qualified mechanics (some in the trade for in excess of 25 years) and have been suprised by some of their incorrect answers. What do you think??
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Have a guess.. you may suprise yourself!!!
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OK you have not mentioned what engine you have. Firstly I would guess that one of your sprockets is fitted backwards but then how would you see the timing marks? Secondly there are two holes in your cam for the sprocket locating pin & you are uti Edited by user Friday, 14 September 2007 10:58:46 PM(UTC)
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I take it that it isnt anything obvious like offset bushings for Cam timing, or incorrect gears.
j
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I take it that it isn't anything obvious like offset bushings for Cam timing, or incorrect gears.
j
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Keep the shiny side up, and the greasy side down. |
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Some good points jim5.0 the engine is a 4.5lt o/head cam straight 6 efi 80series landcruiser engine, though the engine type is irrelevant in this instance. This mistake could be easily made on just about any engine I can think of whether it be a small blo
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Ok is it half a tooth retarded or advanced?
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it,s i/2 a tooth advanced.
If I line up the cam timing mark exactly where it should be the crank timing mark indicates it is at 9 degrees btdc
There is 40 teeth on the cam gear and 20 teeth on the crank gear
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Bugger that has shot my next theory to pieces. I was going to suggest the tensioner was pulling it back a bit but if it's advanced.
It's not a redundancy thing allowing for future timing chain stretch is it?
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Bugger that has shot my next theory to pieces. I was going to suggest the tensioner was pulling it back a bit but if its advanced.
Its not a redundancy thing allowing for future timing chain stretch is it?
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some good suggestions jim5.0!
the crank sprocket was 1 tooth out...
with the gear ratio being 2 turns of the crank sprocket to 1 turn of the cam sprocket. How ever far the crank sprocket moves the cam moves half as much. Example : crank moves 180 degree
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But you said that you had lined up the timing marks so how could you have it 1 tooth out?
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Sorry... poor explanation on my part.
I lined the engine up at TDC going by the timing marks on the harmonic balancer, so the crank timing mark was lined up 100% but the cam gear was out 1/2 a tooth.
The vehicle came to me after someone else had removed
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