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Discussion Starter #1
Im in the process of swapping my heads...bent valve. :(

The tensioner lifting square has a crack through it, does this effect its operation or will it give me problems later on? Looks like its still working as it should and you can still lift with bar to set tensioner with needle nose pliers...with no problems.

will try to post pictures later.
 

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If the crack is limited to the square area and it will terminate (if it grows) towards the outside without the likelihood of spreading towards the inside plate area, then it is OK (IMO) to reuse - although it probably makes installation a little bit more tricky. When you rotate (slowly) the bearing with needle plier, check that it can rotate freely and smoothly or you'll find a loose T-belt after the engine cools down.

What caused the bent valves? If you question whether there was any slight possibility it was related to the same tensioner (e.g. loose belt), then a new tensioner is a cheap insurance.
 

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I'll give you Alfisto Steve's answer, "It's only money, buy a new one." :D
Charles
 

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Im in the process of swapping my heads...bent valve. :(

The tensioner lifting square has a crack through it, does this effect its operation or will it give me problems later on? Looks like its still working as it should and you can still lift with bar to set tensioner with needle nose pliers...with no problems.

will try to post pictures later.
Also are you sure outer spring is not broken?
 

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Seriously, if the lug is cracked, it's been over rotated (or over forced) and that outer spring is suspect. The lug was overstressed from the tensioner being bolted down too tight while trying to rotate, it most likely, but still, that outer spring is so important that I couldn't trust it myself. You just don't know if that spring bore some of that over forcefulness.
Charles
 

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Personally I would not take any chances, replace it. I had to eat a few tensioners in my life but it was worth it. I had a tensioner installed on a customers car started it up and the tensioner needle just did not act right IMO.
Was not fluctuating at all. Not to say there was anything really wrong with it but in All the tensioners I have done I have never seen one not fluctuate slightly. So I tossed it and replaced it with a new one that looked to be fine. I just had a feeling, so out it went. I am sure that maybe it was OK, but 10 miles down the road my customer throws a belt. No thanks. I can eat the tensioner over that hassle and $$$
Really it is only money, it's either another $100 or another $1000+. You have to make that decision! ;)

Jason
 

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The bit surrounding the square broke on my detensioner when I installed it and it has been fine for over 30K miles. I don't think that if it is cracked it necessarily means that the detensioner has been over rotated. If you're using a long extension to do the twisting, I think it would be easy to put too much force into the plate perpendicular to the plane that it's supposed to be rotating and break the backing plate outside the square. (like I think I did)
 

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Seriously, if the lug is cracked, it's been over rotated (or over forced) and that outer spring is suspect. The lug was overstressed from the tensioner being bolted down too tight while trying to rotate, it most likely, but still, that outer spring is so important that I couldn't trust it myself. You just don't know if that spring bore some of that over forcefulness.
Charles

And that is why I stress using needlenose pliers to rotate pulley over center as you lift on lug because of that design flaw that allows/forces you to apply brute force to get tensioner housing to move and lug is stressed and secondly the over center snap effect stresses and may break outer thermal clutch spring.
 

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The toughest mechanical engineering class at MIT I had to take was called 2.30- it focused on the properties and behaviors of cracks.

In a nutshell, that whole course can be summarized with the statement, "cracks propagate".

I think that does say it all.

Throw the tensioner (or is it a de-tensioner ;)) in the garbage...
 

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Discussion Starter #10
new one on its way (thanks Jason)....will post pictures when I get home. I had a funny feeling about using it and you guys confirmed my feelings.
 

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The toughest mechanical engineering class at MIT I had to take was called 2.30- it focused on the properties and behaviors of cracks.
If you had McClintock (if he was still there) that explains this ;)? He started to use finite element program to predict creep crack growth and I was the RA at one time (needed the money) ...

In a nutshell, that whole course can be summarized with the statement, "cracks propagate". ...
Yes, that's very true! That's why they have to inspect airplane periodically but I bet they have some criteria before they throw away some airplanes. I'm sure they all have some micro cracks :eek: - just don't think about this when you fly :)! Some cracks grow very fast and some don't move in ages, it depends on how much stress exist at the tip of a crack and where it points to.
 

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heres the crack in the lifting square...
It is probably nothing but better to be safe than sorry.

Lets remember that there is lots-o-heat in there with lots of expansion and contracting going on! Cheap insurance. May have been fine until you really needed one.

I think you made a good choice.
J
 

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Cracks in metals don't just magically show up. There was either over-stress condition on the square drive, as suggested above, or there was some really bad flaw in the underlying metal from which the tensioner body was made. Neither option leaves me satisfied. I've thrown away tensioners just because "I don't know" that it's right. It hurts the pocketbook, but it's worse when the tensioner fails. The P.O. for the wife's car probably suffered a spun bearing because of a cracked outer spring on his 164S engine, followed by two teeth advance on both cams. 8 of 12 valves replaced, plus the crank.
 

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Discussion Starter #15
Finally got the heads on!!! Torqued to 22 in sequence then 51 then 72ft/lbs, backed of 90 degrees and re-torqed to 72. (correct tightening procedure?) Just waiting for the new tensioner and saab front engine mount. Here are some pictures. Man do i miss driving the alfa. :( almost there
 

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