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I think I am off a tooth?

2K views 17 replies 9 participants last post by  Dikdaan 
#1 ·
I recently changed my timing chain rails and I fed in a new chain used the factory feeding tool. Everything went well except I feel like the timing is off a tooth. I installed the new MB tensioner I purchased and it does move back and forth a bit while I rotate the engine (I assume this is because it does feed off engine oil pressure). I attached pictures to help me explain my situation

Passenger side cam at tdc


Crank at TDC



Drivers side cam at tdc



Passenger side at 20 degrees



Crank at 20 degrees



Drivers side cam at 20 degrees



When I pulled the cover off (chain and pads were not done - engine has 75k miles on it). I assume this is chain stretch.




The engine spins over freely with no issues at all. Part of me thinks this might just be resolved when the tensioner actually has oil in it and it pulls the passenger side cam counter clockwise a bit? I checked slack in the chain on the passenger side, it does exist. I then rotated the cam counter clockwise slightly to pick up some of the slack. Can anyone with experience in this matter help me out?

Thanks
 
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#2 ·
My initial thought is it's off a tooth. A new tensioner comes pre-loaded with oil, so it should not let off enough slack for it to be that far off. But anything is possible, and there's a reason you want to make sure everything lines up. From what I've seen, even with a new chain you'll typically see it a bit behind the mark because of wear on the sprockets and such. That's the big thing that makes me question that: it appears the cam is advanced. If it skipped a tooth while you were cranking the new one in, I'd think it would retard that cam, I can't see it advancing it. How much difference did it make turning the came counter-clockwise? Keep in mind you want to use something to grab the two cast protrusions on the passenger's cam (between the lobes, I think first or second pair, but not sure) to rotate it. If you can get the marks close to lining up, it's probably ok.

One other possibility is the passenger's side may have an offset woodruff key. If the timing is adjusted to factory specs with a stretched chain, the procedure would call for an offset key that would advance the timing of the associated cam, and that would move the timing indicator as well. It's not too hard to advance or retard a cam by a tooth. I've done it using a couple vice grips to hold the chain to the sprocket. I got the master link in the middle of the sprocket, used the vice grips to hold the chain while I worked it back a tooth on the tensioner side first, and then turned the cam to take up the slack and moved the other side of the chain up a tooth. This was to advance it a tooth, by the way. It's hard to explain, really, but it makes sense when you're looking at it. Assuming you do need to do that, just make sure you're certain of which way the cam needs to go in relation to the chain, and that you have something holding both ends of the cam to the sprocket at all times (you may be able to fish out the inside portion of the chain with a magnet, but probably not the tensioner side!).
 
#4 ·
Thanks for the help! I rolled it back one tooth and it looks better than when I took it apart.


As is (tensioner installed, rotated crank a few times)



When I rotate the cam counter clockwise slightly (to alleviate any slack in the chain)




It appears to match yours almost perfectly. I assume I am good to go now? I think this summer I will take some dial indicators and adjust it with a woodruff key since it is not exactly on the money. It also matches the way the car was before I took it apart (I bought the car from the original owner and I have all the service records - chain was never touched).
 
#5 ·
As long as your mark on the sprocket is "coming into" the mark on the cam bearing you should be ok. What I mean by that is as you turn the crank clock wise the mark will move from left to right so to speak. Line up the damper pointer first and if the sprocket mark is slightly "before" the mark on the cam bearing you will be good.
 
#6 ·
Pretty sure you're ok now. I can't picture it in my mind, but I think my SEC looked about like yours does on the passenger's side with the crank on TDC. I did add an offset key on the passenger's side, mostly guessing how much. I think it was three degrees, six at the crank. I've also thought about going through the service manual procedure for setting cam timing. Most of the reason I haven't is because it involves replacing one of valve spring on each side with a light-tension spring to avoid pumping down the lifter. I'm sure there's some performance to be gained in it, I've heard 6-8 degrees retarded on the right side is a typical amount of wear and stretch, and even half that can have a noticeable impact on the power curve.
 
#7 ·
I have a question on timing marks. I tore down the cam area on my 88 SEC in the last few days and here is where I am at. The inside of the engine looks very clean and yes the timing guides do look brown. I also thought the wear on the cam gears necessitated changing them (more bucks), but when I line up the cam marks on the cam towers both are pretty much right on but the crank is at 20 degrees. That seems like a lot and I question is it possible there is one tooth off on the crank sprocket? If everything is new what would one normally see as to timing on the crank. I would assume close to zero. Thanks.
 
#8 ·
It's been a while since I did the timing chain project but aren't there very specific guidelines in the manual? If you're not using it, I think you should get a copy.

Be advised the cam marks are only for assembly. They get you in the ballpark and are probably adequate but to truly dial in the cams, you need to follow the manual's instruction for that procedure. You'll need a manual lifter and a dial indicator gauge.
 
#9 ·
20 degrees is huge. If your chain is that stretched it's entirely possible your cam gears are worn. I think you can find pictures of good and and worn gears to compare. Either way when you put your new chain in then it will be easy to see if the cam marks line up again.

usually one cam is off, simply because there is about 40% the chain between the left and right bank. So that is odd that they are both aligned now.

Also use the right cam marks to check chain stretch, not the left for that same reason.

I dont know the formula for what one tooth is in degrees, You could always pull both gears off and reset and then measure again.

turn the crank around 2x and look for a replacement link on the timing chain to see if it has been replaced.

BTW, you will notice a definite improvement in horsepower when you are done!
 
#10 · (Edited)
Here is a picture of the right cam tower with the damper at zero and the drivers side cam spot on. This just seems like a lot for a chain stretch. I guess I will put the new parts in and see how that affects it and then decide if I am one tooth off or not. If I see a master link in the old chain that means someone elses fingers were in the pie before mine and might have made a mistake. I will let the crew know, thanks
 
#12 ·
Well this is strange. The passenger side was off one tooth. No master link so that means no one has changed it from the factory. The old gears looked fine and did not show much wear against the new ones. The inside of the engine is spotless which means it was well cared for. The guides were light brown but not a lot of wear and the old tensioner was still doing its job. With the new chain, and gears, along with moving the passenger side ahead one tooth everything is dead on. So one of two things happened. The factory installed it one tooth off or it jumped a cog so to speak. I just don't see how that is possible though. If the gears were bad or the tensioner was loose then yes but with everything in good shape..... any thoughts? Has anyone seen this before? I will certainly double check it a couple of times but right now I have the valve keeprs off since I still have to replace the valve seals. Maybe I will finish the work this weekend and get to drive this for the first time?
 
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