Second 164S tensioner failure!

Alfa Romeo GTV6 Forum: Engine: Second 164S tensioner failure!
By Michael Harris (Admin) on Thursday, September 23, 2004 - 07:55 pm:

Tensioner Pic

I converted my car to use the 164S (Thermal/mechanical) timing belt tensioner back in 1999 or so when I installed the 3 liter engine. It worked fine until I replaced it with a new unit in 2002 or so because I thought the original one was getting a bit old. The spring broke a few weeks later as you can see in the image. I was lucky - no valve damage though the passenger side cam did jump quite a few teeth. I chalked that one up to bad luck and reinstalled the tensioner from 1999.

I drove the car like that till earlier this year when again, I decided to replace the original 1999 tensioner with a new one. The same thing happened yesterday (spring has broken in exactly the same place) so I had to reinstall the old one again. I've only done a few hundered miles since the installation. Again, I was very lucky that my valves were not damaged and I was able to limp home.

Any opinions on this or similar experiences? I though it might be an error I am making when installing or tensioning the device but then surely my old 1999 one should have broken by now too?

I want to install something which will be reliable, I donít want to have to worry about the spring breaking again - and I think that this means that I have 2 options:
- Go back to the original Alfa tensioner mechanism and rebuild it often.
- Install the Alfa Heaven STAYBELT MANUAL TENSIONER (

Does anyone know if itís even possible to revert to the original tensioner (having drilled, tapped and sealed the oil return hole) once you install the 164S unit? Will the oil return seal up OK?
Are the rebuild kits still available for the original Alfa tensioner? I must admit that itís a lovely piece of engineering in comparison to the Alfa Heaven or the 164S kit!

I'm am tempted to go the Alfa Heaven route since I do suspect that the adjustability might be a bit of an overkill on Alfa's part. My Porsche 951 does not have any type of adjustability in the timing belt and Porsche recons you can do 60K on a new belt. Both engines are Aluminium though the 951 has a 4 cylinder. Longer stroke so might be more susceptible to block expansion. Zat says you can do 30K using the Alfa Heaven tensioner which sounds pretty reasonable.

Any opinions much appreciated!


By JimGreek on Thursday, September 23, 2004 - 10:00 pm:

Hi Michael,
I hope my mech.tensioner is no distant relative to your failed ones!I've had mine on the 3liter for 7 years now and all is ok. I have some experience on the subject though you may benefit from.Before this device,I had the original Alfa unit on BUT,as I was pissed off with repeated leaks,I removed the hollow oil-supply stud, plugged it up and then reinstalled it in place, so,no oil!I disassembled and cleaned the tensioner,lubricating the piston O ring and lower seal with silcone grease.Then,the return hole was plugged up.I reassembled the tensioner and put it back,tightening the belt using the tensioner's own 2 springs,inner and outer.To check the adjustment,I rotated the engine.The determining factor,was the ability to twist the longest belt travel (driver's cam to crank pulley)90* by finger pressure alone.This test is actually proposed by many manufacturers using similar belt drives for adjusting their fixed tensioners.I used this setup for about 3 years on street and track without problems (I do replace the belt yearly)and of course no leaks. Why did I switch to the thermostatic type?....Would you believe...looks? How about...weight?? Guilty on both counts!I honestly believe that what I described is the safest solution.I also believe that the Staybelt is ok, even if it doesn't look good (you're right!).
Jim K.

By Michael Harris (Admin) on Thursday, September 23, 2004 - 10:21 pm:

Thanks for the advice Jim!
I'll consider that.
One thing which occurred to me is that the failures I have heard about are with moderately 'new' tensioners - so perhaps your '97 vintage and my '99 vintage tensioers are okay but the newer ones have some sort of build flaw in them?

By Zamani on Thursday, September 23, 2004 - 10:35 pm:


I've had good luck on all my mechanical tensioners. My mechanic installed them.

I was wondering, if you look at the tensioner, and you look at where the spring breaks, why didn't Alfa just make the casting extend all the way to follow the curvature of the spring? I think due to the spring's lack of thickness and tension, it is failing at the point where it is not supported by the aluminum casting.

What do you all think?

By Allan on Thursday, September 23, 2004 - 10:55 pm:

My mechanic Toni who worked for Alfa in Italy for many years, and is working for Rick Demilian now in Sydney, pulled my one apart blocked the oil pin and filled it with high temp grease.
He says that is a common solution in Europe.

By IndianaMark on Friday, September 24, 2004 - 09:31 am:

I put a 3.0 rebuild in my car a couple years ago and labored over the tensioner choice. Bottom line is about reliability. The mechanical unit has been suspect enough to make me not want to roll the dice. I put a Zat fixed tensioner on and no problems since. What I did to make it easier to tweak the belt tension was to carve a section out of the timing belt cover with a dremel cutting disk directly above the tensioner and I can adjust the belt tension in a matter of minutes without taking off belts or hoses. It also allows you to check belt tension at the tensioner at the same time as between the pulleys. And yes there is slightly more tension when it is hot than cold, but I have an older Volvo with a factory fixed tensioner and no issues. If you get adequate tension when cold (not piano wire tight) then there should be no issues when hot.

By Gerry on Friday, September 24, 2004 - 05:41 pm:

Michael, My experience was exactly the same and it broke in precisely the same spot. As an engineer who spent most of my career in materials failure analysis, there is no question in my mind that this an extremely marginal design. A case of a localized shear force being applied at a significant stress riser (Yep, Zamani got that right) meets minimally adequate cross sectional strength.

As well as my Alfa's, I had an MR2 turbo for a number of years and when changing the belt and tensioner on it (routinely at 60K) I couldn't help but notice that the tensioner was almost exactly the same design but the cross section of the spring at that failure prone point was 4 or 5 TIMES the wire section used on the Alfa device. Its beyond me what these guys were thinking.

Anyway, after my experience, which pretty much mirrored yours, I went to the Zat device a few years ago simply out of expedience. Its been fine and I have made a few very minor adjustments. Next time that I'm in there I may switch back to the original tensioner without the hydraulic portion connected. There's some good logic in going that route as you still retain something of a spring tensioner. I think elsewhere Nizam provided a discussion and it is all valid in my opinion.
Just my 2 cents, your mileage may vary,

By Greg Gordon on Friday, September 24, 2004 - 05:49 pm:

This may sound crazy but I don't even worry about that spring breaking. It's the other spring inside the tensioner I am scared of. If the internal spring breaks the belt will skip, period. The external spring can break and as long as the belt is set with enough tension it doesn't really matter.

As a side note those tensioners with broken springs make excellent supercharger belt tenioners.

By JimGreek on Saturday, September 25, 2004 - 08:23 am:

All right Greg,there's the magic word again! I'm waiting for a complete bolt-on kit WITH detailed instructions in Greek (heheh!)at a price I can afford!
Jim K.

By kevin on Saturday, September 25, 2004 - 09:01 am:

Hi Michael, Barry made a bullet proof tensioner which is on my GTA engine. Im sure they are pics of it on that thread. He put a bolt right through the existing tensioner with two locking nuts each side. Some people might disagree with this method but my 164 has it and one of Dawies race motors.
With this method I chainge my belt every 40 000km which I have just done in my 164.
I have seen a few tensioners also break right through the boby of the tensioner aswell on the 156's.
By the way I have been destroying nearly everthing on the road lately with the GTA conversion into 1983 GTV except for the M5 BMW which got away at 150kmh today.

By Greg Gordon on Saturday, September 25, 2004 - 01:30 pm:

Instructions in Greek? I have not even written instructions in English yet. What "magic word" are you talking about?

By JimGreek on Saturday, September 25, 2004 - 11:40 pm:

The word SUPERCHARGER Greg!What's happenning there?
Jim (still atmospheric)K.!

By Greg Gordon on Sunday, September 26, 2004 - 06:47 am:

OH, that word. Well what's happening is I can't update my web sight because of some server problem being worked on at that end. The information on page 6 is still fairly current anyway. The kit works and it's awesome but I keep finding minor areas to improve and I don't want to release it until I am really happy with it. If you want to know something specific just E mail me and I will answer it.

By JimGreek on Sunday, September 26, 2004 - 09:07 am:

Nah,you just about covered it all. When you get to the point of having everything ready AND idiot-proof, I'll forget about the Greek manual and give you a call (maybe...Swahili??Hah!)
Jim K.

By Michael Harris (Admin) on Wednesday, October 13, 2004 - 12:37 pm:

I just experienced another tensioner failure!
Larry of Alfa Parts Exchange is sending me an original, stock Alfa tensioner which I'll modify to use. He suggested I can weld closed the stock oil feed stud - anyone done this before?

By Peter K. on Wednesday, October 13, 2004 - 01:16 pm:

Yes, I did.
It was sugested by our Dutch AR importer long ago.
I didn't feel good about it though.
By welding the oil feed stud, the hydroulic system that takes care of the detensioning at cold start and at high rpm's is not working.
Putting a lot more stress at the timing belt!
So after one season, I bought a new stud, and overhauled the tensioner, It started to leak after only a few hundred miles.....
But the oil was not getting to the belt!!
Oil on the belt is most times because of a leaking front crankshaft seal!
I think the overhaul kits today are far more better than before, and by using synthetic oil, it's well possible the have no more oil leaks at the tensioner!

By Mike Halasz on Wednesday, October 13, 2004 - 02:14 pm:

Yes and no problems after 10 000 kilometres.Simply in the initial installation, the belt tension is set for a cold motor with an expectation that the correct tension will eventuate upon the motor heat up and the expansion of the block. Care is required not to hard rev the engine until it is warm. In practice this is not a problem as the there is enough torque in the motor to get around anyway under2-3000rpm. I am using a modified original Alfa ensioner that is manually adjusted if and when necessary. It works fine. I originally installed a US made mechanical tensioner that cost me around $120 AUD but it was so badly made that it leaked straight away. It now sits on the shelf. (Hence the modification of the original Alfa unit.)

By Alfisto Steve on Wednesday, October 13, 2004 - 07:31 pm:

How does a mechanical spring tensioner "leak"? Also the "USA" made mechanical spring tensioners are made in Canada according to stamping on the 60588421 tensioners I have seen.

I have been running this style tensioner since 1993 without any problems.

By Alfisto Steve on Wednesday, October 13, 2004 - 07:42 pm:

I might add though that I have changed about 6 or 7 for my friends who have had outer spring break at same place shown in pictures.

I believe most of those spring failures are due to over torque of tensioner during installation.

That spring wraps up tight very quickly and if you lift tensioner with a 3/8" drive hinge handle or even a proper torque wrench without using a pair of needle nose pliers in two holes in pulley to rotate pulley as you torque tension you can break spring and never know it.

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