I let my timing chain slip and cant find TDC - Hot Rod Forum : Hotrodders Bulletin Board
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Old 07-18-2009, 05:49 PM
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I let my timing chain slip and cant find TDC

Hope I'm ok asking a Nissan question here.
I have a Nissan 4 cylinder motor with a dual overhead cam . I was just changing the timing chain when I messed things up.
The instructions were to get crank and valves lined up to compression top dead center. No problem. I stuck the crankshaft bolt in and turned it to the timing tdc marks to get ready to pull the chains.
In loosening the crank bolt I spun the crankshaft in reverse rotation within the chain because I had taken off the tensioner and guide( big mistake)... see picture.
My problem now is trying to line things back up because I don't know how far the cranks spun backwards. Anyway I attached a pic- you can see the slop in the chain and in trying to move the pistons I am contacting the valves. Not hrd but enough that I feel the tension.
I'm probably making this harder than it needs be but can someone guide me on trying to get the crank back in sync with the valves. I am overly worried about bending a valve.. maybe they don't bend that easy.
I know what I did wrong just trying to fix it. Making a simple timing chain replacement into a major PITA. Could I have already damaged a valve. Each piston has 4 valves and they are angle in the head. I was going to do a leakdown and comp test when I get things back together.
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Last edited by Berg; 07-18-2009 at 06:51 PM.
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Old 07-18-2009, 05:54 PM
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You can see in the above pic that the two cams are at TDC in the pic( note the colored chain link and the marks on the cam sprocket--
they are no longer in that position.
After the lower chain moved I messed with both the upper and lower and cant figure it out. The yellow dots are teh tdc mark locations where they should be but are not.
I am real paranoid of bending valves... and I did not want to pull the head at this point.

thanks for any suggestions

Last edited by Berg; 07-18-2009 at 06:53 PM.
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Old 07-18-2009, 07:13 PM
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I guess the best thing to do is to remove the valve cover and check the positions of the cams.

Don't know if this can help:

Here
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Old 07-18-2009, 11:07 PM
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valve cover is off.. I can see valves/cam lobes etc... just worried about valve to piston contact trying to find tdc..just don't want to mess up the valves
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Old 07-19-2009, 01:25 AM
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You won't bend the valves that easy. Turning it over by hand won't hurt a thing. Don't go forcing anything, but no worries.

Many times, setting the cams on their marks will let you turn the crank freely. Set your cams and then set the crank. If you hit a valve, don't worry. Just adjust the cam(s) one way or the other until you can turn the crank.

Pull the plugs to make turning easier. That way you're not fighting compression and thinking you're pushing against a valve.
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