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2G Loose spot in timing belt???

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my98gsx

Supporting VIP
797
290
Aug 14, 2005
Wappingers, New_York
As the title says I am scratching my head over this... My timing is spot on, brand new idler, tensioner pulleys, as well as hydraulic tensioner. The belt tightens up once the engine is rotated, but there is a loose spot - a very loose spot. I read that aggressive cams could cause a problem (I am running kelfod 272's) but I am afraid to run the car like this. Has anyone ever had this happen and/or know how to fix this issue? Thanks
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If in doubt, get another belt and see if it still does it, or make sure when you are doing the tension, that all of the slack is on the tensioner side. I used zipties on the cam sprockets to hold it in place, then pull it tight over the oil pump and crank sprocket. If you run it like it is, you will defiantly not have a good time.
 
It sure appears that the hydraulic tensioner is fully extended and cannot take up the slack in the belt. I hope I am wrong, but I would pull the front cover off and double check. I know it's not fun, but better to be safe than sorry. I have a 90 that I am going to have to do the same thing with. I think I can hear the tensioner lever hitting the water pump bolt at idle and it goes away at cruising speeds but knowone wants to wreck a head. I have had a loose belt before and posted pictures just like yours, only had stock cams. Mine were fine BUT, I couldn't pull up on the belt and show that many cam gear teeth, that would scare the siht outta me.
Anyone else got some input??
 
The belt is a brand new mitsu belt, not a gates etc... I just ordered all new parts - both tensioners, and the idler. I also ordered the rod style timing belt tensioner tool, which I have never used before, may be some help.

Thanks for the input so far.
 
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Here is what you WANT to see with the front cover off......
If the belt is that loose, I would want to double check that you can still put the grenade pin into the tensioner. Re-examine and adjust as needed. The timing tool is super handy and I have 3 of them for the motors I have.
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That belt is way too loose. I would absolutely not run the car like that.

You'll need to pull the lower timing cover to see what the problem is. If I had to guess, the manual tensioner loosened up, or the auto tensioner is set wrong. Either way, something is definitely off, and you'll bend valves if it's not corrected.
 
It looks to me like you may have an extra tooth between cam sprockets. Rotate the exhaust cam 1 tooth clockwise and try to tension it again. It may look like the cam gear marks dont line up when you do this, but don't worry about them until tension is set again and you have spun the motor over a few times. Pulling tension on the tensioner will draw that cam back in an anticlockwise direction, and you will probably end up dead on.

I have run into that in the past, and that is how I fixed the issue. Your problem may be something else, but this is a free check...

Best of luck!
 
rabenne - that was my issue prior to being tuned, it drove me crazy! I kept changing the exhaust timing marks by one tooth. Im going to post the pics below of the two settings... One with the exhaust timing rotated one tooth. After scratching my head for days I just chalked it up to the fidanza cam gear marks being off... The question is, which one is right? both look messed up. (the car was tuned with the timing belt set as-is and it made 563whp, so it does not seem the timing was off)

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I am going to have to agree with you. If shes making that kind of power, you probably don't have the belt installed incorrectly. This may be purely a tensioner issue. The slack there would make me very nervous, but I am not sure what you can do short of replacing the auto-tensioner and starting over.

I am glad you checked this, it is one of those things that has got me in the past. Based on your pics, the top one is correct.


To distinguish which alignment is correct, you could zero the cam gears out and watch an indicator on the cam with a degree wheel on the crank. That would tell you if the cam events are happening at the correct crankshaft rotation. Or maybe I am just really tired and this isnt making sense to me.
 
No, you are making perfect sense - these cam gears will not align with all 4 marks. My tensioners come today I hope this solves the issue. I have seen that the marks on fidanza gears have been off in the past, but i dont want to grenade a fresh engine for some shiny pulleys.
 
With a degree wheel you could ensure they are aligned to crankshaft revolution regardless of the cam gear marks... It will take some work, and it wont be fun, but it is totally doable.
 
these cam gears will not align with all 4 marks.

By design all 4 marks shouldn't line up. The angles are different between the marks for the intake and exhaust cams. What's supposed to line up is the bolt centerline and the inside timing marks with the top surface of the head/rocker cover interface.
 
steve,

I remember thinking this on stock cam gears at one point. In the correct position, with inside lines and bolt centerlines all in-line, are the outside marks above or below the line?
 
are the outside marks above or below the line?

I don't have any reference materials up here in the mountains so memory may be faulty...

IIRC the intake cam mark sits at 270* relative to the dowel. The exhaust cam mark is offset something like 3.4* degrees so it's 90* - 3.4* = 86.6* relative to the dowel. I think that makes both outside marks above the actual centerline but it's late and I'm old and stupid.
 
Steve, to add to what you are saying, then the top pic - where the inside lines meet, in-line with the head/valve cover is correct. Even though the exhaust cam mark is off on the outer edge? I pulled the belt numerous times messing with one tooth here, and one tooth there. Its odd that 3 out of the 4 lines line up... I am using the cam locking tool as well, which only fits when the cams are aligned perfectly. I am going to reference my friends car since it happens to be in my garage at the time being as well. This has stock cam gears installed, and runs great (when he is not blowing brake lines haha).
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Cam lock could be part of the problem. They aren't needed and can actually cause the slack between gears... Not that this is your problem for sure, but that was my initial impression, and hearing you are using the gear lock makes me think that is the problem even more. I bought one about 10 years ago, tried to use it once and realized it wont let you get the proper tension on the belt between gears, and threw it in the trash.
 
For some reference I'll post what my belt looked like when the tensioner rod protrusion was about 0.195 inches. That's the number that is supposed to be between 0.150 and 0.180 inches. The belt was visibly loose at the top between the cam sprockets and it was the most loose I've ever had on my car. But it was nowhere near as bad as what you show in post #1. Fixed it soon after this pic was taken.
As with yours, this slack would pull out immediately upon turning the crank clockwise a bit with a wrench, and the car ran great.
The tape measure doesn't help anything with this pic all by itself, but I made a series of pics showing pushing up or down on the belt with a finger, with the tape measure behind.

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Thank you to everyone who posted on this issue. Ive been on here since 2005 I believe and I have never had such good information posted on a thread.

We're on boost - that timing mark information made me feel so much better.
Rabenne - You were 100% right... that cam lock tool, which I have been using for 10+ years kinda does suck... I took your advice and did without it this time around. The belt tension is SOO much better! I will only be using this tool for head storage now.

After replacing all the tensioners the belt does not have any slack now. (Granted I only ran the car for 5-10 min but i did not see any loose spots). I really think it all had to do with the hydraulic tensioner. I will run the car some more tonight, but I think the problem is resolved. Thanks again
 
You are welcome! I'm glad it is looking good now.
One more thing worth mentioning - That 15 minutes you are supposed to wait to measure the protrusion of the tensioner rod - it makes a big difference, and it wasn't obvious to me which way the number would go. So I measured every few minutes and wrote it all down, like a log of it. It becomes less. Somewhere in the neighborhood of 10 to 20 thousandths of an inch less after 15 minutes. After 15 to 20 minutes it stops changing.

So the point is, if you set the protrusion initially to say 0.150" (the minimum value) and just leave it like that without checking 15 minutes later, you will wind up with the belt too tight! The protrusion will be less than 0.150". I have a scan of my measurement log if you want to see it posted, but it is pretty messy LOL.
 
Your question about why all 4 marks don't line up, I think is answered by this from the FSM:

You would use just the 2 inner marks, not all 4.

86* 55', that's not bad memory for an old guy. I think there is another that shows that the exhaust cam is advanced that 3.something degrees too.
 
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