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#1
06-24-2007, 03:33 AM
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Could the Cam chain out by one tooth and still run o.k.?
Well I finally finished puting in my new chain and tensioner and made sure it never cam away from the sprocket at anytime.
The timing marks however still look to be out by the same amount as before, when the Dampener is on 0 deg the RHS sprockets mark is on the right past the TDC mark on the housing. ( This equates to about 15 deg on the Harmonic Dampaner). The LHS sprocket line up perfectly, I though this was due to stretch in the chain. The RHS head seems to have had work done to it before as the oil tube fittings are a different color to the other side and there is some red text on the front like it's been away to a shop for a rebuild. Is it possible that who ever done the work before had the cam out by 1 tooth in the clockwise direction? The engine seemed to run fine for the 4 years I've hade it. I removed the tensioner again and moved the chain forward one tooth, put the tensioner back in, turned the engine over by hand several turns and all the marks seem to line up much better. Now the mark on the RHS sprocket is the width of the mark itself to the left of the mark on the housing. What do you think ? Regards Damian 
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#3
06-24-2007, 11:36 PM
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It is unlikely the cam was out by one tooth. It is more likely you are allowing the cam to advance clockwise due to cam to valve spring action. This is one reason taking the rocker arms out has an advantage. Make sure when you check the timing you rotate the crank only in the clockwize direction and do not pass TDC (This is hard to do). If you pass TDC rotate the cranckshaft at least 20° counter clockwize and approach TDC again. The trick hear is to make shure the cam is always being pulled. When at TDC verify that the timing chain is tight on the pull side of the cam (For us Americans that the driver side, In nautical terms, is the Port Side). If the cam chain is loose on the pull side it means the cam was advanced forward by the valve springs. And yes you can also take out the chain slop with a cam wrench.
John Roncallo
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#4
06-25-2007, 04:56 AM
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With the new tensioner in the chain seems to be fairly tight all the time on the pull side. There is a small difference but nothing like when there was no tensioner in there at all.
If I turn it very slowly approcheng 0 deg on the vibration dampener, it still seam to be passed it's mark before the dampener lined up with it's TDC mark. After I moved the chain one tooth, forward with reference to the cam gear now the dampener and LHS line up perfectly and the RHS seems to be about 5 deg before it's mark (measured on the Dampeners scale). This looks closer than before ???
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#5
06-25-2007, 09:21 AM
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Check both of your cam gear woodruff keys. You may have an offset woodruff key installed. If you do, it will look like it is halfway sheared. These are used to correct timming and I belive they are avalable up to 12° correction. The marks on the camshaft are really reference marks for assembly. A new chain should always put the gears within 1/2 mark with standard keys. More accurate timing is done with the offset woodruff keys.
John Roncallo
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#6
06-25-2007, 12:25 PM
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Damian:
According the the manual one tooth off equates to about 18 degrees. It also indicates checking #1, then cross checking #6. Have you done this and noted the timing mark position? Also, the factory method involves measuring valve lift on #1, and #6, and then comparing the rotation to the specified degrees for that cam at that valve lift. Is this how your work was done? But, John is probably right on about the offset key business... 230/8
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#7
06-26-2007, 12:12 AM
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Yes thats the real proceedure also when you do this the hydraulic lifters for #1 and #6 need to be replaced with solid lifters tools for this check. Generally people just put the chain in and verify the marks are close. Thats all I did and I keep saying to myself that I am going to purchase the 2 solid lifter tools, a set of offset woodruff keys and finish the job correctly. I have been saying that for 2 years and 35,000 miles now.
John Roncallo
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#8
06-26-2007, 12:58 AM
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Thanks,
I did have a look at the woodruff keys when I had the gears off and they looked like the standard ones, mind you I didn't remove them. would the ofset one look any different from the outside? Both the old and the new chain/tensioner combo seem to have the same amount of offset (engine has only done 130,00 miles). Unless they re-ground the cam and it seemed to time better with one tooth of advancement However I'm starting to think by the quality of workmanship that is displayed on the previous work done to the head ie, crack in the valve cover that was welded up and kinks to the oiler tube at the fittings. Maybe they were just slack when they reassembled it, and got it a tooth out? mmmmmm a solid lifter tool would by handy. Damian P.S anyone know where to get some oiler tubes for a M117.962 from?
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#9
06-26-2007, 12:27 PM
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Quote:
It might be hard to tell if the keys are offset without a really good cleaning in the area. All wear mechanisms I can thinkof would cause the cams to retard. Shaving the head will also cause cam retard. I would try retarding the sprocket one tooth and see how it looks. But before doing anything remove all plugs and manually rotate the engine 720° each time you reposition the chain. John Roncallo
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