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Discussion Starter #1 (Edited)
So, I have searched and read some various BB opinions, but came up with conflicting and/or inconclusive opinions and no clear picture of what NOT to do! (As much as I have worked with the 24 valve tensioners now, I am still a 12 valve virgin.)

My 12 valve street car belt and tensioner was done by Group 2 some 2-3 years ago, so it is time to dive in again! It's been great however, this time I would like to hear what's out there, and know what I am getting (for no particular reason other than my own morbid curiosity!)

What did these cars come with? (GTV6 and Milano/75 V6...?)

There was a hydraulic and a mechanical tensioner - what were the differences? How did they work? What failed? What was the Zat conversion? Who sells what now? What is the best to go with?

Please advise.
 

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All GTV6, 75/Milano, 164 came with the hydraulic tensioner. Alfa had a recall on the 164 to replace hydraulic with mechanical, I believe. I think most Milanos are updated to mechanical. I have used the mechanical tensioner exclusively on my Milanos and never had a problem. But, I'm sure there are other experiences. Some say that problems with the mechanical tensioner is due to improper load on springs during installetion (over-load). The 164 section has the most info on the proper installation of the mechanical tensioner - look for some of Steve's posts on the subject and the Alfa service bulletins.
Jes
 

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I think the hydraulic tensioner with the oil hole weled up is the way to go.

do a search and you will see time and time and time again bent valves etc with the thermocrap toy Tensioners

last time I looked I could not find one case with the hydraulic type. not counting things like never changeing the belt or towing with the car in gear spining the motor the wrong way.

With the old one there is not much to go wrong. But the new type seem to have a ton of things go wrong all the time. do a search for failed tensioner or bent valves. and see which type comes up over and over and over again.
most with low miles too.

that is my $0.02

P.S. if you have the chance to hold both in you hands you can see how crappy the new is vs the old one.
 

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I'm another one for the "plug the oil feed, and use the beefy hydraulic tensioner" camp.

I don't "just" use this method for my track car. For years my Milano (the same one I track) was also my daily driver. No problems with the tensioner, or early belt failure, or leaks from the tensioner area.

In fact, my wife's Verde which continues to be one of the daily's (going to hit 260K miles on my way home from work today) has been on the modified hydraulic tensioner for over 130K miles .... four belt changes according to my records with no ill side effects. The bearing continues to spin freely with no noise.
 

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Discussion Starter #6
OK guys - thanks. Now how about the issue of purchasing from an Alfa dealer versus buying THESE TWO PARTS SPECIFICALLY from say Riccambi, Centerline, IAP etc... OEM or not - does buying THESE TWO PARTS SPECIFICALLY from the independents constitute aftermarket...?

What should I expect to pay?
 

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For a start, the hydraulic part of the tensioner assembly "DE-TENSIONS" the belt as the hydraulic pressure rises: i.e.: when the rengine revs rise. The assembly is designed to have highest tension when the cams are... I suppose the best way to explain it is flip-flopping on the lobes at low speed (idle or starting). At higher speeds the tension on the belt smooths out and therefore the higher belt tension is not needed.

The spring strength in the tensioner without oil pressure behind the piston (the oil pressure is fed to the plunger side, not the back) is too high (with oil feed plugged) for constant use.

This is fine if you want to replace your belt every 30,000 km (19,000 miles for you people living in the dark ages), but if you would like to get the full life out of your timing belt reliably, have it like the factory made it. These Alfa guys knew what they were doing when they designed the rest of the engine... why do you think they did not know how to design a timing belt tensioning system???? This device is often misunderstood and when properly set up is very reliable.

In the mid 80's, Alfa Romeo Australia issued a Tech Bulletin saying weld up the hole, only to find that V6s everywhere were spitting belts quite reliably at 50,000 odd km. An Alfa engineer was sent out from Italy to see what was happening. The story was that Alfa hit the roof when they saw what was being done! They issued another bulletin explaining the system and why it was that way.

I will admit that the hydraulics rarely last more than 100,000 km without leaking. My advice is to put new seals in the tensioner (and anywhere else at the front of the engine if they are leaking) everytime the belt is replaced. And: polishing the 8mm shaft in a lathe with fine emery to be sure.
 

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Interesting discussion. From what I recall...:rolleyes:

The original hydraulics failed in part because of reduced tension as a result of sporadic oil pressure and/or the leaking seal allowing the belt to get soaked with oil (unnecessary lubrication where you don't need it).:eek:

Tom Zat's original solution was to plug the port, install a bracket with an adjusting bolt to mechanically tension the belt by pressing against the tensioner roller. This would be fine in a static environment but made no adjustments for thermal expansion (what the oil did in the original design).:confused:

The new tensioners have a unique metal spring that adjusts for heat expansion but are particular in how they are installed. The installation procedure may seem simple but the proper alignment of the adjusting marks is vital. Once properly adjusted, they seem to work fine. By design they are less robust than the hydraulic units as there is less involved in maintaining tension.

I purchased one 3 years ago for $70 and is still in the box (original AR).;) Difatta, IAP, Centerline may range between $115 - $130. Nuff said.

Good luck.
 

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In the mid 80's, Alfa Romeo Australia issued a Tech Bulletin saying weld up the hole, only to find that V6s everywhere were spitting belts quite reliably at 50,000 odd km. An Alfa engineer was sent out from Italy to see what was happening. The story was that Alfa hit the roof when they saw what was being done! They issued another bulletin explaining the system and why it was that way.
Haha, funny. It's funny how many times I start working on a car, and I can't understand why a part won't come out, or something seems a$$-backwards, when the reality is that I just need to start thinking like an engineer and find out WHY it's designed that way, and WHAT it's trying to accomplish before attempting to modify or service it. Then there are other times, when a bolt is too long and I have to take off an intake manifold assembly or jack the engine up an inch and a half to get the alternator off. That being said, it is good to do your research. The belt tensioner seems to be like everything else on the car, as long as the maintenance schedules are followed, the car operates beautifully; modifications as far as handling, mounting and performance aren't a bad idea at all, and some may even raise the value of the car (depending on the audience), but messing with the core engineering of the car and it's accessories is not recommended, there will be consequences. having to change the belt twice as much being one of them.
 

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For a start, the hydraulic part of the tensioner assembly "DE-TENSIONS" the belt as the hydraulic pressure rises: i.e.: when the rengine revs rise.
You sir, are correct. Mea culpa.

We generally abuse the term "tensioner" when it is, as a matter of fact, a de-tensioner. On the other hand, we also misuse the term "roll bar" when it is really an "anti-roll bar". :D

As for cars throwing belts when the de-tensioner is set statically, well, maybe I will just count my blessings that after a cumulative 250,000 miles (we're still in the dark ages here) across two 3.0V6's (30,000-mile, not kilometers, belt change interval), I haven't seen abnormal wear on the belts.
 

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I once had a customer that came in with a GTV6 with bent valves. The car had about 140,000 km on one timing belt. It was dry but you could peel the individual teeth off the belt with your fingers, it was that old and worn. There were few oil leaks at the front of the engine, so the failure was not oil leak related. It had stripped the teeth right off the belt where it wrapped around the crank pulley while idling at the lights (cams had just stopped, but crank had turned enough to do the damage).

He was perplexed, saying: "I rev the crap out of this car all the time and do lots of hiway kms, so why did the belt let go while it was idling???

It took me a little while to figure out that at idle and start-up is when the belt needs the tension and the most stress is on the teeth. It also proves that the factory set up is very good while there are no leaks.

What is the system on the current 24 valve V6s (or sadly just departed for crappy GM V6s) like?
 

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(or sadly just departed for crappy GM V6s) like?
I'm going to go completely offtopic for a second and jump on this comment.

I was lucky enough to get handed the keys to an Auto V6 Brera with 500kms on the clock last week and took it for a half hour drive, and then engine surprised me. At idle, it sounded exactly like our Auto V6 75. At WOT, it still had the very definitive Alfa V6 snarl. Got up and flew as well. So Alfa really know how to make their engines unique, even when using a GM block.

*end hijack*

ROCK ON
R~R
 

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Ok, am now very nervous about my de-tensioner.

Think it is hydraulic. Suspect is has had the oil hole plugged - is there an easy way to know, short of a belt and de-tensioner change?
 

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Would anyone buy the argument that belt quality/strength has improved with time? Perhaps that is why a non-detensioning (plugged) belt tensioner works?

SamW, speak up! How many timing belts and mech tensioner installs have you done now, with zero failures? Over a dozen?
 

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Ok, am now very nervous about my de-tensioner.

Think it is hydraulic. Suspect is has had the oil hole plugged - is there an easy way to know, short of a belt and de-tensioner change?
Oh no! Now that you've read this thread, your bearing will seize and all the teeth on your t-belt will be shredded!

Never mind that your car has been running fine up until this point :D

To see if you have one version or another, you can visually look at the detensioner and tell the difference. There is no need to disassemble the timing belt cover to inspect them.
 

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I just look at the track record. the oil weled up works. I am at somthing like 240,000 miles with one. never had a belt problem yet. I would like to get a new one I just put in new grease every 100,000 miles or so. but as a rule the water pump will let you know when it is time to change.. I think you are crazy not to change the belt at least by 60,000 if not sooner. heck I did it once in like 15 min. before work one day. the part that takes the most time is leting the coolent out. to remove the hose. if the only fear of the welded up it the belt might go bad some where over 100K
vs the one that seem to fail at 2k 5k 10k 15k 20k 25k 30k etc. I will take the one that wiil last over 100K and change it at 30k or 60k when ever my water pump starts to leak.

as for how it worked in the first place where the oil PSI let it lose. I have to say I never felt good with that. when is the oil PSI very hi. when the block is cold on start up. where is the most stress on the belt? on startup and when it is cold..

I think is is very clear from the track record this is one place where alfa did not do so well.
there is a few things that are very bad in this system.
The amount of wrap is to small
the square type teeth that are more prone to hop out.
and the crapy detensioner.

But you have to look at when this motor came out. it is a very old. and was never up dated.
if you look at a *** car ther belts now are good for very long runs but they do a test run of more then I would guess all the alfa v6 ever made. It is to bad alfa never went back and up dated the front after a few things were known to industry about belt driven cams.

but I guess they are resource short. and they had to do the 24V then move on the diesel etc. and they seem to not ever go back to the old to fix things. I can see why, they were a very cash poor at the time.
 

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Discussion Starter #18
Who is charging what these days for belt and tensioner...?
 

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Sorry DaveH, I have been on vacation this week, putting in a rebuilt transaxle and drive shaft in the Verde and a 164 Alt also, then I need to pull the starter out of the spider for a rebuild... I love vacation time!!!

Let me think, I have 235K miles on the GTV6, bought it with 120K, so 4 on that one, plus changing out your hyd for a mechanical, plus the mechanical on my Verde, plus DonG's GTV6 prior to selling it, I think he is running the the sealed hydr unit on his Milano now... Anyway, the reason I have stuck with the mechanical was because Charlie at Spruell (prior to be sold off) said he only used mechanical units, never had an issue and saw lots of issues with the original hydr units. We never discussed the sealing of the oil rod, but I think Charlie had done so many V6 t-belts that he should know best... Anyway, I am sure both of mine will snap on me this week now that I have Jinxed myself....
 

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We have 3 GTV6 3L cars with the original oil activated detensioner. Never had a problem with it and very satisfied that this system assures high tension at start and lessens tension at rising oil pressure in order to reduce belt wear. The whole system is patented of the chief engineer at Alfa that time. One of our friends, absolutely convinced that the oil detensioner was sub standard, changed to the new mechanical tensioner system. This engine had stiffer valve springs from IAP. At start the belt jumped over and the piston was stopped by a valve. Quite shocked from this event he could luckily find that no harm was done. The belt was put right again and I think the tensioner was blocked so it could not let loose another time.

Fortunately our cars have not had any such problems with the old system. No problems with oil leak or jumping over teeth. So we see no reason to change to the new system at present time.
 
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