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I've run into an interesting dilemma. I'm doing my timing belt / water pump on my 98 Mazda 626 2L and am at the point of putting the belt back on, but something has come up.

I checked my timing marks before taking the belt off ( and a few other times for other reasons ) and always assumed that everything was OK, as to my eye it looked like the timing marks were aligned.

However, as I was putting the belt back on and looking at the Haynes manual I noticed that it said the timing marks should align even with the surface of the head. However my marks were aligned one sprocket tooth below the the surface of the head. Of course you can hardly see anything in the Haynes manual pictures, so I took a look in the WSM:

enter image description here

That picture indeed seems to show the marks aligned with the surface of the head. However some of the other WSM graphics are less clear and to my untrained eye seem to show the marks aligned slightly below the head surface:

enter image description here

I've been dogged by a rough idle which I can't seem to solve ever since I bought this car, and I have no idea who the last mechanic to change the belt was, although I am sure it probably was the lowest bidder, let's say.

This is a non-interference engine, so it's quit possible it's been running with a slight misalignment of the marks for years without any physical damage.

As a novice, my question is do I leave well enough alone, or take a chance and rotate both cams up one tooth so the marks are dead on with the head surface like the Haynes manual says?

POSTSCRIPT Nov. 10th 2016

So I went ahead and made the marks align with the head surface, ran the engine for a few minutes and it seems to be OK:

enter image description here

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    Since it's a non-interference engine you risk no physical damage if you decide to give it a go. The risk vs reward is something only you can judge – Zaid Nov 8 '16 at 13:54
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    @Zaid My basic issue is I don't want to put it all together and then see it's misbehaving and have to redo it. It's 3 or 4 hours work. I'm hoping someone might just know what is correct. – Robert S. Barnes Nov 8 '16 at 13:59
  • Do you know what is the valve lift and duration? – Zaid Nov 8 '16 at 14:23
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    @Zaid I decided to take your suggestion and just go ahead and try it. I have a feeling that it's the right thing to do, since if I aligned the intake timing mark with the head surface previously, the exhaust mark ended up like two teeth below the surface. I'll be quite gratified if this finally solves my idle issues. – Robert S. Barnes Nov 8 '16 at 16:08
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When you check the timing previously, you may have noticed the marks being slightly off because some belt stretch.

Install the new belt according to the manual (even with the head is very common) for proper valve timing.

  • Actually, I locked the camshafts in place before removing the old belt, and the timing marks where definitely aligning about one tooth below the head surface. I decided to go ahead and realign the camshafts as per Zaid's suggestion and the difference is quite obvious to me at least. Still marking you up since you're telling me that even with the head is the common way it's done. – Robert S. Barnes Nov 8 '16 at 16:07
  • @RobertS.Barnes So it worked? Could you add an answer that says that, please. – Zach Mierzejewski Nov 8 '16 at 20:36
  • @ZachMierzejewski I haven't finished putting everything else back together yet. Once I've got it together and running I'll put some kind of update here. – Robert S. Barnes Nov 8 '16 at 20:47

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