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Finished up the putting the new heads on and timing the engine!
Just want to reassure myself that everything is working properly.

I set the tensioner to the nominal mark while the engine was cold.

Is it perfectly normal for the pointer to drop below the nominal mark to compensate for the hot engine bay temperatures correct?

The pointer does return smack dab in the middle when the enigne bay is totally cool thought.

Maybe im crazy, but i just dont want to hear the valve bending song

I cant wait to get this baby back on the road!
 

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Sounds like tensioner doing its job.
 

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Tensioner doing its job? I've been considering this issue recently. The design philosophy seems to be to have increased tension when the engine is cold (presumably starting) and then to back off when running. This seems to have been due to Alfa recognizing they had too little t-belt engagement on the gears. More tension at startup means less likelihood of skipping teeth. Relaxing tension during running reduces bearing/bushing wear to improve longevity.

But the oil-fed (de)tensioner backed off when the engine started getting oil pressure. The mechanical job backs off when it gets warm. If you do a hot start, there is no mitigating measure to compensate for the low belt engagement. I'll bet I'm not the only one who starts his engine no matter whether it's still hot from running or has been sitting outside through a winter night. So....just _what_ is the tensioner's job? Why is the mechanical one better than the stock tensioner with the oil passage blocked off?

I know, this has been rehashed more times than most of you want to think about. But I don't recall noticing if the issues were being presented this way to me before -- noting that the thermo-mechanical (de)tensioner does not apply the force at hot start that was the whole reason for this tensioner mess.

Michael
 

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Michael I think if you relook at it you will see if tensioner pointer is below reference point when hot belt is tighter not looser. The timing belt is more likely to be loose at cold start. How loose I believe depends on whether thermal clutch outer spring is broken and how free pivot point is to move pulley eccentric.

We just did timing belt on my son's S month ago beacuse of water pump leak and I found belt very loose cold and then found binding ecentric on pivot pin so changed tensioning when we did pump.
 

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OK. One conclusion I draw from this is that the tensioner is NOT intended to accomplish an starting timing belt tension at start of engine and then relax that as the engine runs. The mechanical tensioner appears to be designed simply to maintain a fairly uniform tension across the ambient to operating temperature range. This is not at all what the oil-fed tensioner seems to have been designed to do. Given the limited travel the tensioner has, it would seem to me that just using a well-fashioned and well-lubricated spring with a suitable elliptical cam design (ever look at modern compound bows?) would give a constant belt tension across the entire temperature range. But I'm not a mechanical engineer.

I guess that my initial response (two posts above) was directed at the question of just what the mechanical tensioner is intended to do with its dual spring, bi-metal temperature compensation.
 

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Finished up the putting the new heads on and timing the engine!
Just want to reassure myself that everything is working properly.

I set the tensioner to the nominal mark while the engine was cold.

Is it perfectly normal for the pointer to drop below the nominal mark to compensate for the hot engine bay temperatures correct?

The pointer does return smack dab in the middle when the enigne bay is totally cool thought.

Maybe im crazy, but i just dont want to hear the valve bending song

I cant wait to get this baby back on the road!
I always set the tensioner pointer just ever so slightly below the mark.
 

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I guess that my initial response (two posts above) was directed at the question of just what the mechanical tensioner is intended to do with its dual spring, bi-metal temperature compensation.
Is it perhaps intended to allow the alloy V6 to 'grow' - would the blocks expand slightly in two directions and thus make the belt noticeably tighter?

If so, it wouldn't matter that the de-tensioning occurs during a hot start.

-Alex
 

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And that would mean that the "de-tensioning" of the bimetallic strip is not important, no? And that would mean that a plugged oil-fed tensioner would be appropriate, no? And that would mean that the susceptibility to broken secondary springs and skipping time on backward rotation is unnecessary, no?
 

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And that would mean that the "de-tensioning" of the bimetallic strip is not important, no? And that would mean that a plugged oil-fed tensioner would be appropriate, no? And that would mean that the susceptibility to broken secondary springs and skipping time on backward rotation is unnecessary, no?
Sorry - I don't quite follow. :confused:

De-tensioning of bimetallic strip is supposed to slacken belt with increasing temperature - I believe. What I was saying was to answer the concern of what happens with a hot engine - yes, the bimetallic strip would be in the 'hot' position, but then so the engine blocks would be still expanded as well.

Plugged oil-fed tensioner - this is going to have a single set tension for all engine speeds and temperatures, isn't it? As long as this starts off not-too-tight, I don't see a problem?

Broken secondary springs - I have only seen this with the later, mechanical tensioner. Also, I have only seen the 'slack belt when cold' problem with the later, mechanical tensioner. Having said that, oil pressure is greatest when cold, so I would have guessed that the hydraulic tensioner would also give a slack belt when the engine is cold. But, crucially, not before the engine is cranking over.

Cheers,
-Alex
 

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Your comments following "I don't quite follow" are exactly what I meant. The mechanical tensioner has a thermal component which seems to be meant to relax the tensison for an operating engine. Its crucial differences with respect to the oil-fed device are that it seems mechanically fragile (it is subject to breaking after abuse, but its tolerance for abuse is small), and that it does not re-apply higher tension at hot start. This means to me that if the added tension to the t-belt is essential to skipless starts, then the mechanical tensioner is inadequate. If the added tension is not essential, then neither is the mechanical tensioner and the old tensioner with the oil passage blocked is adequate. Blocking the oil passage prevents the old tensioner from leaking oil onto the belt and self-destructing the engine. These are my present opinions on the tensioner question. They would lead me to design a better spring-loaded tensioner if I were a mechanical engineer assigned to the t-belt system.

Michael
 

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The mechanical tensioner has never lived up to its hype. I remember installing the upgrade kits when they came out because the local dealer was over flowed and they contracted the shop I worked for to do the upgrades. The mechanical tensioner has caused as many problems as it was supposed to fix.

The oil feed unit works well with two items to look for - 1. minor oil leakage 2. the bearing would get tight on the pivot. As long as the oil feed units were serviced every 25k-30k miles they worked well. I prefer the oil feed to all the other units out there. My second choice is ( getting nomex suit on ) Zat style fixed tensioner. The Zat unit is not the most elegant design, but it works for the life of the belt as long as it is properly tensioned. Many complain it does not allow for belt stretch and temp change, but almost every other engine with a belt in production has a tensioner just like it - and their belts go 60-90K.

This is just my two cents.
 

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Were I designing such a device, I'd try to limit the tensioner travel to just over what the thermal range indicated was necessary. I'd try to keep the tension range limited, too, using eccentric cams as _necessary_ to keep the belt tension within a well-justified range. It may be that the older tensioner does this without eccentrics. It would be interesting to have a measurement, but I suspect I'll never get this, nor do I have a way to interpret what it would mean just now.
 

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IMO, the key word is "tension"! As long as the timing belt is tensioned (i.e. having some minimal amount of tension) all the time then there'll be no trouble! The belt will not jump teeth except in an unusual condition (e.g. one of the pulley has trouble turning). I would say the engine can even rotate backward as long as the belt does not slack off in the reverse direction.

In my experience (or perception), the 24V timing belt put a lot of tension of the belt. The belt will get cracks and hint of the teeth marks at the smooth side of the belt after some use - evidence of pretty high tension IMO. Next is 12V with hydraulic tensioner. The spring is much stronger (than the mechanical one) and it seems to tension the belt much tighter. The mechanical one is more convenience, more available and easier to work with than the hydraulic one. It is not perfect - it is not as sturdy, the spring(s) can fail, the bearing pivot area can seize and another disadvantage that we haven't talked about much is the "limited" range that it can move. IMO, we do like to have a tensioner that can move to maintain the tension of the belt ALL the time. If the tensioner bumps into a movement limits, it will either increase belt tension quickly or become loose. At the tight side, all the engine expansion will have to taken/absorb by the timing belt. At the loose side, the belt will start to get more slack and this will increase the possibility of pulley jumping teeth.

A fix tensioner is probably OK (IMO) for hotter regions where there's no wide ambient temperature swing. Engine (like most things) does expand when it gets hot. The timing belt will see more tension (due to engine expansion) when the engine gets hot. The engine will see temperature, let's say, from 50F to 230F in a warm/hot region. But in a colder region, this range will be increased. It might see temperature range from 0F to 230F so there's an additional 50F difference (you can use your numbers). The wider the temperature range, the timing belt will just see more stretching and loosening cycles. I would think it will be a good idea to check and replace the timing belt more often if a fixed tensioner is used.

Ideally, I would like to see a more reliable mechanical tensioner with slightly stronger springs (thus a little bit more tension) than the current mechanical one. It should provide a smooth and reliable movement range to accommodate cold and hot engine cycles with minimal tension changes exerted on the timing belt.
 

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Your comments following "I don't quite follow" are exactly what I meant.
...
If the added tension is not essential, then neither is the mechanical tensioner and the old tensioner with the oil passage blocked is adequate. Blocking the oil passage prevents the old tensioner from leaking oil onto the belt and self-destructing the engine. These are my present opinions on the tensioner question. They would lead me to design a better spring-loaded tensioner if I were a mechanical engineer assigned to the t-belt system.
Thanks for that - I'm pleased we agree after all :)

I see what you mean now. It's also interesting to think about the wider thermal range in a cold climate. Fortunately the temperature is rarely below 5 degrees here (degrees C), so I reckon that I'll stick with the oil-fed tensioner as it seems less likely to break. I think a cambelt inspection is necessary with every oil change... I always change them before the teeth outlines show on the smooth side of the belt. My experience on FIATs is that high tensions create odd noises as well, so I tend to go for less rather than more.

I agree with your idea, Michael, for a re-design - recently I changed the cambelt on a large Honda four (2.2L) with the balance shafts, and I was struck by the solid design of the tensioner. The tension was set by a light tension spring, acting on a 10cm (sorry, 4in. ;)) lever, and then the centre nut was fixed in place, rather like the old FIAT SOHC engines. The actual tension when set in this way (the Honda-prescribed method) did not seem tight, compared with that old yardstick (wrong, I reckon!) that the belt should just turn through 90 degrees with thumb and index finger. The large bearing itself (on the Honda) seemed like new.

Actually that brings up an interesting point that I'd do well to learn - do you guys use metric or imperial when you work on metric cars like the Alfa? I don't want to stand on any toes by implying that you wouldn't convert metric-to-imperial without thinking, but my understanding is that everyday measurements in the US are imperial (or 'British' I think it is called?) In NZ we use imperial measurements occasionally when convenient (!) - tyres are inflated in psi, usually, and we talk about 'mileage' to mean distance in kilometres - but everyday measurements are metric, and degrees C.

However I can never remember how to convert Farenheit to Celsius - something to do with 9 and 32 - all I remember is that 212 = 100, 32 = 0. Oh I suppose then it must be divide-by-9 and take off 32... :)

Thanks again for the summary/clarification,
-Alex
 

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The mechanical tensioner has never lived up to its hype. I remember installing the upgrade kits when they came out because the local dealer was over flowed and they contracted the shop I worked for to do the upgrades. The mechanical tensioner has caused as many problems as it was supposed to fix.

The oil feed unit works well with two items to look for - 1. minor oil leakage 2. the bearing would get tight on the pivot. As long as the oil feed units were serviced every 25k-30k miles they worked well. I prefer the oil feed to all the other units out there. My second choice is ( getting nomex suit on ) Zat style fixed tensioner. The Zat unit is not the most elegant design, but it works for the life of the belt as long as it is properly tensioned. Many complain it does not allow for belt stretch and temp change, but almost every other engine with a belt in production has a tensioner just like it - and their belts go 60-90K.

This is just my two cents.
I agree with andrew. The oil fed is much better. I plan on some day installing mine again (I have brand new units, with feed studs etc..).
The new t/belts out these days won't stretch anyways. They are also resistant to oil and other fluids now. Yes the oil can make it slip. But the old thinking of the belt stretching when heated and contracting when cold is pretty much gone now.They have Self-Lubricating Fabric which Provides Exceptional Resistance To Abrasion, Resulting In Extended Pulley And Belt Life, The Molded COG Design Runs Quieter And Is More Economical Than Chain Drives, High Modulus Glass Fiber Non-Stretch Cord Delivers Precise Length Stability

Timing belts are made of synthetic rubber, neo-prene,
highly saturated nitrile (HSN) or other
materials designed to take drastic changes in temperature.
Their reinforcing fibers make them vir-tually
unstretchable, but they do wear out. The
combination of constant bending and flexing,
combined with heat and tension, fatigues the rein-forcing
strands and hardens the rubber. This can
lead to cracking, fraying and ultimately failure. Which is around 50K for the 164. I may be pushing it but really I think 30K is too soon unless you beat the crap out of it?;)
Whether or not this is all 100% true, I don't know. I suspect there may be minimal stretch to the point that it makes no real difference. I would be more worried about proper tension. Regardless I always set the tensioner pointer below the mark as mentioned. Never had an issue with that set up.

I have not had any issues personally or professionally with the mechanical if gentle with the adjustment of it. Usually the skipped belts that come in where done by someone else. Once I reset them this way there has been no issues. Not saying the mechanical tensioner is stellar in design but ain't all bad either really. Does it's job.
The problem with the hydraulic is the pulley is no longer available, in-fact nothing is available for it except the rebuilt kit.
More Europeans use it that we do here in the US.

I honestly think that with normal driving that the belts of today can really go much longer than 30K. I have done 40k+ with the belt still just fine when replaced.

Anyways, thats my opinion!!

JAson
 

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. The problem with the hydraulic is the pulley is no longer available said:
Not really true, IAP sells bearing #02754 for tensioner seperately and it is same bearing used on 24v tensioner pulley. http://www.international-auto.com/index.cfm?fa=p&pid=2508&posid=861422&noapp=1

Listed under their Alfetta, GTV6 and Milano ball and roller bearing section in catalog. I have one in stock and I know it fits the oil fed tensioner as well as 24v timing belt tensioner pulley.
 

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Not really true, IAP sells bearing #02754 for tensioner seperately and it is same bearing used on 24v tensioner pulley. http://www.international-auto.com/index.cfm?fa=p&pid=2508&posid=861422&noapp=1

Listed under their Alfetta, GTV6 and Milano ball and roller bearing section in catalog. I have one in stock and I know it fits the oil fed tensioner as well as 24v timing belt tensioner pulley.
yes yes sorry, I totally forgot that one for some reason? Hope those stick around!!
 
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