Anyone installed the new Centerline Staybelt tensioner? - Alfa Romeo Bulletin Board & Forums
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post #1 of 30 (permalink) Old 03-15-2019, 02:41 PM Thread Starter
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Anyone installed the new Centerline Staybelt tensioner?

It aint cheap, but if it works better then the mechanical tensioner I have now, I think it's an almost essential upgrade, given the consequences of failure.

https://centerlinealfa.com/catalog/s...belt-tensioner

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Staybelt Timing Belt Tensioner
Timing Belt Tensioner 2.5 and 3.0L SOHC V6 (All)

Our exclusive new Staybelt Ultimate tensioner is a mechanical, semi-fixed timing belt tensioner that maximizes the utilization of newer belt technology and eliminates the shortcomings of both original Alfa Romeo timing belt de-tensioner designs. An update of the original Staybelt tensioner developed by Tom Zat of Alfa Heaven, this design has been rigorously tested on the street and the race track to give you maximum protection against slipped timing belts.

The Staybelt Ultimate is easy to install, simple to adjust, and fits any 12V (SOHC) V6 engine used in the GTV/6 1981-86, Milano 2.5 and 3.0 1987-89, and 164 (all) 1991-93. Does not fit 24V (DOHC) engines used in 1994-95 164 models. Does not require re-use of any part of the original timing belt de-tensioner.

The Staybelt Ultimate is manufactured exclusively for Centerline in the USA. It is Zinc plated for corrosion resistance and is backed by a lifetime warranty against defects in materials and workmanship (including the bearing).

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post #2 of 30 (permalink) Old 03-15-2019, 06:34 PM
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I don't get the paranoia over the factory mechanical tensioner. Who has in fact suffered an engine failure from this part?
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post #3 of 30 (permalink) Old 03-15-2019, 07:22 PM
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I have a friend whose 164 was towed and they let it roll backwards in gear. Belt jumped and bent valves. That won't happen with this tensioner.

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post #4 of 30 (permalink) Old 03-15-2019, 07:48 PM
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Quote:
Originally Posted by Alfistaa View Post
I don't get the paranoia over the factory mechanical tensioner. Who has in fact suffered an engine failure from this part?
Just do a search.... you'll see for yourself. This is well known across the board.

In recent years, I sense the failures have decreased due to a better knowledge base (that means Alfisto Steve and certain others here who contributed greatly), and probably improved tensioner quality control. I know that's not a scientific nor analytically supported statement, but I do know for a fact that the current crop of tensioners in inventory are superior to the first batches, made at a Canadian supplier facility. Those units became infamous for snapping thermostatic clutch springs, where they were staked into the back of the tensioner body. I have a good Alfista friend here who put two successive new tensioners on his Milano, and both failed within minutes, wrecking his valves. And he is a very competent and thorough mechanic with decades of racing experience.

It's not so much the possibility of failure, it's the failure mode that is terminal. After all it's an interference engine, and that means serious damage is the consequences of tensioner failure, as someone pointed out.

I showed this new tensioner to my son Mike, who has an '86 GTV 6, that runs a perfectly good mechanical tensioner installed by the (competent) PO, with a new belt in 2013. At this point, a recent inspection showed the indicator pointer to be right on target, where it should be on a warm engine. But Mike and I agreed, given the fact that nothing lasts forever, his modified 2.5 is getting a new fixed tensioner and belt from Centerline this summer. It's like an insurance policy on your motor.
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post #5 of 30 (permalink) Old 03-16-2019, 04:34 AM
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It also means that you don't have to worry about inadvertently turning the engine backwards when you are working on the driveshaft.

Ed Prytherch
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A little government and a little luck are necessary in life, but only a fool trusts either of them. - P.J. O'Rourke
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post #6 of 30 (permalink) Old 03-16-2019, 08:55 AM
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I have a build ongoing with a crate NOS 3.0, and my driver 3.0, both with Mech tensioner. The original hydraulic tensioner on the crate motor replaced with Mech unit. Rationale? Two of the best Alfa shops in the USA, one in Livingston, NJ and one in Tacoma, WA recommendations. Not saying that the fixed tensioner isn’t a super and perhaps better alternative. The oil feed has already been plugged on both engines perhaps I will convert one since I still have the NOS hydraulic tensioner to modify or use the Centerline unit. Too bad both engines have new/nearly new timing belts and tensioners. Not likely to put 30k miles on either one soon, the belts are more likely to “age out”. No denying the advantage of not risking belt slip when the engine is rolled backwards. I have never done that in 25 years of driving v6 with Mech tensioner, but it is a recurring bad dream.

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post #7 of 30 (permalink) Old 03-18-2019, 01:14 PM
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What I don't understand (perhaps out of ignorance) is how this is better to the current mechanical tensioner. Doesn't tension need to be somewhat variable depending on temperature, age of the belt, etc? Eventually this would need some sort of adjustment, right?
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post #8 of 30 (permalink) Old 03-18-2019, 01:26 PM Thread Starter
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Well, heres how I understand the argument. The seals in the original oil-fed detensioner were crummy, and the thing would start leaking eventually, or at especially inopportune moments.

The mechanical piece was technically an upgrade but was prone to spring failure, at least until recently. Because of the ongoing issue of dubious reliability, recently some guys figured out how to rebuild the hydraulic part with new/better seals and it seems a fair number of people who had swapped for mechanical were going back to the original but upgraded setup.

This Tom Zat-based design being sold above is a mechanical piece but designed to remove the failure points (the rollback issue for one), and doesn't require you to open back up the oil feed tube IF you'd previously swapped hydraulic for mechanical. Seems like solid insurance to be, because of the spring breaks then you've essentially mulched your valvetrain.

A lot of people still swear by the hydraulic original with the new seal design, regardless. I guess your position depends on your experience and your current setup.
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post #9 of 30 (permalink) Old 03-18-2019, 04:31 PM
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Quote:
Originally Posted by chairmankaga View Post
Well, heres how I understand the argument. The seals in the original oil-fed detensioner were crummy, and the thing would start leaking eventually, or at especially inopportune moments.

The mechanical piece was technically an upgrade but was prone to spring failure, at least until recently. Because of the ongoing issue of dubious reliability, recently some guys figured out how to rebuild the hydraulic part with new/better seals and it seems a fair number of people who had swapped for mechanical were going back to the original but upgraded setup.

This Tom Zat-based design being sold above is a mechanical piece but designed to remove the failure points (the rollback issue for one), and doesn't require you to open back up the oil feed tube IF you'd previously swapped hydraulic for mechanical. Seems like solid insurance to be, because of the spring breaks then you've essentially mulched your valvetrain.

A lot of people still swear by the hydraulic original with the new seal design, regardless. I guess your position depends on your experience and your current setup.
This is a pretty good overview of the situation. Each of the existing Alfa Romeo designs has strengths and weaknesses. I will add a few data points to the discussion:

In addition to the known issue of leaking seals, the original Hydraulic-style de-tensioners do not work very well in extreme cold temperatures. If it's cold enough to prevent proper oil flow, there will not be sufficient oil pressure to feed the de-tensioner. I know this is an esoteric failure point, but it's one that Tom Zat told me played a significant role in the development of the original Staybelt tensioner.

The Mechanical-style de-tensioner was developed as a warranty fix for leaking Hydraulic units, and was installed as a retrofit on many cars at the dealership and became the de-facto solution in North America. It was never widely adopted in Europe. It does work well, if installed and adjusted properly. However, as people have noted it can release tension if the engine is turned backwards, or if the engine backfires. It also seems to have a greater failure rate on high compression/highly tuned engines.

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post #10 of 30 (permalink) Old 03-19-2019, 07:57 AM
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Originally Posted by JoeCab View Post
This is a pretty good overview of the situation. Each of the existing Alfa Romeo designs has strengths and weaknesses. I will add a few data points to the discussion:

In addition to the known issue of leaking seals, the original Hydraulic-style de-tensioners do not work very well in extreme cold temperatures. If it's cold enough to prevent proper oil flow, there will not be sufficient oil pressure to feed the de-tensioner. I know this is an esoteric failure point, but it's one that Tom Zat told me played a significant role in the development of the original Staybelt tensioner.

The Mechanical-style de-tensioner was developed as a warranty fix for leaking Hydraulic units, and was installed as a retrofit on many cars at the dealership and became the de-facto solution in North America. It was never widely adopted in Europe. It does work well, if installed and adjusted properly. However, as people have noted it can release tension if the engine is turned backwards, or if the engine backfires. It also seems to have a greater failure rate on high compression/highly tuned engines.
Joe, can you elaborate on the design of this new one? How is it "semi-fixed"? Is there a spring involved? Or is it just using an eccentric bolt to adjust the tension and it stays a fixed tension?

On a side note, I imagine Tom Zat might have run into cold oil issues living in Minnesota. And I'm guessing the Italians never tested in cold weather like that.

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post #11 of 30 (permalink) Old 03-19-2019, 01:44 PM
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Isn't it true that the fixed mechanical tensioner is either too loose at low temperatures or too tight at high temperatures?

Most people set it tight a low temps and, therefore, it is too tight at high temps.

The lore was that if you go to a fixed tensioner you need to change the timing belt more frequently because you are putting it under more stress than it was designed for.

Variable tension was the logic of the original design. https://www.alfabb.com/bb/forums/alf...tml#post237620
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post #12 of 30 (permalink) Old 03-19-2019, 01:49 PM
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Well, I'm certainly not working as a young, ASE certified tech these days, nor did I ever, so I cannot attest to all the current designs used in belt tensioners. But I'm willing to bet a six pack of somebody's favorite brew, that there's no other timing belt tensioner out there today with THREE friggin' springs in it! Except for Alfa's mechanical tensioner.

Am I wrong? That alone is reason enough to buy this new tensioner, in my opinion. Simpler is better. I refuse to believe Alfa's V6 expands and contracts any more than anyone else's aluminum V6... with all due respect to Ing. Busso.
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post #13 of 30 (permalink) Old 03-19-2019, 04:02 PM
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Joe, can you elaborate on the design of this new one? How is it "semi-fixed"? Is there a spring involved? Or is it just using an eccentric bolt to adjust the tension and it stays a fixed tension?
That is correct - it is adjusted, locked down, and then it functions as a fixed tensioner. There is no spring.

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post #14 of 30 (permalink) Old 03-19-2019, 04:54 PM
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I modified a stock tensioner to be fixed. I’ve never had a belt failure. Fiats run a fixed tensioner. I know, an iron block but maybe with modern belt technology it just doesn’t matter? Was Alfa just overthinking this in the first place?
I’d certainly use the Centerline version as a replacement

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post #15 of 30 (permalink) Old 03-19-2019, 06:13 PM
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Originally Posted by JoeCab View Post

In addition to the known issue of leaking seals, the original Hydraulic-style de-tensioners do not work very well in extreme cold temperatures. If it's cold enough to prevent proper oil flow, there will not be sufficient oil pressure to feed the de-tensioner. I know this is an esoteric failure point, but it's one that Tom Zat told me played a significant role in the development of the original Staybelt tensioner.
I might be missing something, but I am not sure how this would be an issue. The Busso de-tensioner design keeps the belt fully tensioned for the first few seconds while cranking a cold engine, which is good because that is when most timing belt failures happen. If the ambient temperature is below freezing and it takes a bit longer for sufficient oil pressure to build for de-tensioning, how would that be a problem?

I think the over-complicated Busso de-tensioner design was deemed necessary because of the perilously small amount of belt wrap around the bank 1 camshaft gear due to the adjacent auxiliary shaft pulley. Any other T-belt-equipped engine I have seen has had full belt wrap around both cam pulleys (including the later Alfa 24V V6, which uses a conventional, spring loaded tensioner).

In any case, I have one of the new Staybelt tensioners on the shelf and ready to install during my next timing belt/water pump replacement job. My GTV6 engine had the original de-tensioner operating as a fixed mechanical tensioner when I first bought the car. I opened up the epoxied oil feed stud and rebuilt the de-tensioner using the best parts from two different used tensioner units. It leaked oil, so I re-sealed it again using the good seal kit from Alfissimo, but it still leaks a bit from the shaft seal.

As a Porsche mechanic with a lot of experience with 944 and 928 timing belt systems, I must say the early 944 with mechanical timing belt tensioner works quite well as long as the factory instructions and replacement intervals are followed. At my shop we re-tension any new 944 timing belt (mechanical or later spring-loaded style) after 1,000 miles to account for belt stretch. This would be a wise idea with any mechanical belt tensioner.

Anyway, thanks to Centerline for continuing to support these cars!
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