Chain tensioner questions. Carrera vs 930

[scary driving]

Hello Everyone:

The engine on my 77s (2.7) at some point made a noise that resembled a rattling timing chain. Inwas wrong, but it still made me paranoid and I started buying parts for the oil fed tensioners. I made the mistake of buying a rebuild kit for tensioners from the 930, and upon researching and looking through posts on the subject, although the carrera oil fed tensioners are way more reliable than the spring loaded ones on my 2.7, they are NOT a bulletproof option for piston-valve contact prevention. The carrera tensioners are infact, collapsible enough to have the chain skip the sprocket and you know the rest. There is apparently a kit to put a “stop” on the carrera tensioners sort of like the ones used on the spring loaded ones, but it goes on the inside of the tensioners. Although I did on one post see the picture of the kit, there appears to be no known rebuild kit for the carrera oil fed tensioners that I could find. I bought the tensioners used hoping to rebuild them (and know exactly what I have in there), rather than spend a fortune or risk with reproduction parts. Now I’m stuck with lack of information, so hoping to get answers from the savvier members here regarding what to do: Should I get the 930 tensioners with the collars? Is there a kit to rebuild the oil fed tensioners, since I would place the stops in them (also need a source for these). I need help here. I would like to be able to go on long distance trips on this car and not be sweating bullets.

Thanks in advance.

[SalParadise]

There is no rebuild kit for the Carrera tensioners. None. If you opened one, you would see that there really isn't much in there to "rebuild."

My only worry with the Carrera tensioners is the very cheesy ball-cage affair that is pressed into the top that acts as a valve - when I got my new kit this cheesy cage had already popped out.

You can pop the circlip and put a spacer under the plunger. Several people used to offer a kit to do this. However, I disagree with this on a 911. The tensioner not only keeps tension, but also smooths out the surges in the chain, which can be tremendous when you bring it close to redline and snap the throttle closed.

Sweating bullets over this is pointless. It's like Ducati owners sweating over timing belts and timing belt changes. You just need to install them correctly.

You need to stop sweating bullets over this. It's pointless. You will probably in all seriousness hear the tensioner failing before it goes as you have heard in the past already. There is no bullet-proof fix unless you go to solids, then you have the problem of no dampening.

What you need to sweat bullets about are the ancient fuel lines in your car. This is what needs to be sweated over if you have not done all of them.

[scary driving]

That’s the news I was afraid of getting. I started with all hoses on the car when I got it, that was a no brainer. Save for the tubing (cis lines and under the car) which were thoroughly cleaned, they were all oreplaced. All rubber parts have been replaced too. Everything works on the car. Engine failure is my only serious fear right now, and I’m going to do those tensioners this January. The engine is comming out for leaks and CIS hoses (tubes to box) and pop foo valve anyway, so this is when to do it. I’m running out of time to decide what to do, but I want some sort of “limp home” capable solution, even if it requires periodic service as opposed to just failing catastrophically without warning.

[Trackrash]

Yea, it's all about choices. HBTDT you are taking a risk installing used Carrera tensioners. There is no way to know if they will work correctly for any length of time. I had a used one fail after a few hundred miles even though it seemed perfect on install.

It is difficult IMO to install the safety stops inside the Carrera tensioners. In my case with new chains there was no room for them. In fact when one of my tensioners failed there was not enough slack to allow the chain to jump a tooth. With used streached chains that may not be the case. If you search there is an old thread that shows the method of making and installing them.

If it were me, I would rebuild the original tensioners and use the safety collars. The only advantage to the Carrera collars is the fact that in theory they will last the life of the motor with no maintenance. The old style will require a rebuild every so often. I have heard Porsche recommended every 40K miles.

[scary driving]

Yup, the originals rebuilt with the collars sounds like the reasonable way to go, since I doubt the car will see those 40k miles in the next 10 years. At that point, the carrera tensioners could (assuming they were new) stop making sense, since at 20 years, you should begin to doubt anything that handles pressure and movement (such as o rings, not engine hardware...that was not an invitation to get flamed) and consider replacement. I bought the covers, lines, guides and was hoping to rebuild the carrera tensioners, therefore becoming as reliable as new, since they are oem. The whole not being rebuildable lays my plan to rest. I have new chain guides and rebuild kits for the tensioners, so I’ll add the collars and consider them a maintenance item to be redone every time the engine is out for whatever reason, which I’m sure there will be plenty of those per decade, or every 40k miles or less. By all means, if anyone can point out my blind spots on my plan, please do.

[Trackrash]

+1 on your plan. Plus you can sell your Carrera setup for $.

[scary driving]

That’s true... Make money ‘yall.

[Walt Fricke]

I think Carrera tensioner failure is overrated. I put mine in my '77 2.7 in 1986 or so. Transferred them to the 3.0 it acquired in '89 or so. Still in there, working fine through two subsequent rebuilds.

However, if one fails, you can limp home - just go easy on the throttle.

I don't know if there is a QC issue nowadays or not. For sure the external valve is not a triumph of fail safe engineering. More like a way of saving money in manufacture?

With a suitably tipped Dremel tool you can grind a groove into the side of the hole where the cap holds the spring which holds the ball bearing (pressure limiting valve), and give the cap a better purchase. Better would be someone with machining smarts figuring out how to fabricate a cap which could be screwed into threads cut in the hole to hold the spring but have holes itself to let the excess oil out.

There is a similar cap/spring/ball at the bottom of the plunger chamber. Its function is to prevent oil in the chamber from flowing backward to the supply chamber. Since the supply chamber's pressure is limited, you can't get excess pressure trying to unseat this valve. And the relative pressures are probably fairly equal. I suspect this valve doesn't fail.

There are no seals on the plunger or its cylinder - it relies on a fairly tight fit. I suppose wear could occur, but I've not seen it, and it would have to be pretty significant to affect the operation of the tensioner. It is a part which is certainly well lubricated.

[SalParadise]

Once again, we turn to Kierkegaard on this 911 conundrum:

If you install Carrera tensioners you will regret it; If you do not install Carrera tensioners you will regret this also; If you install or do not install Carrera tensioners you will regret this. If you install 930 tensioners with collars you will regret it; If you do not install 930 tensioners with collars you will regret it...

You get the picture. There is no answer. I went with Carreras but my old mechanicals were fine on my 2.7.

What you should be worried about is the a$$clown driver in his Toyota Corolla about to blow a light or stop sign into your pride and joy.

Once again, this is something you cannot control.

Best of luck, as with any old 911 you'll need it. Just make sure you wear your seat belt and carry a fire extinguisher.

[Trackrash]

Originally Posted by Walt Fricke

I think Carrera tensioner failure is overrated. I put mine in my '77 2.7 in 1986 or so. Transferred them to the 3.0 it acquired in '89 or so. Still in there, working fine through two subsequent rebuilds.

However, if one fails, you can limp home - just go easy on the throttle.

I don't know if there is a QC issue nowadays or not. For sure the external valve is not a triumph of fail safe engineering. More like a way of saving money in manufacture?

With a suitably tipped Dremel tool you can grind a groove into the side of the hole where the cap holds the spring which holds the ball bearing (pressure limiting valve), and give the cap a better purchase. Better would be someone with machining smarts figuring out how to fabricate a cap which could be screwed into threads cut in the hole to hold the spring but have holes itself to let the excess oil out.
.

Agree that when mine failed the car was still driveable.

There was a problem with some aftermarket tensioners that never worked right out of the box. There were a couple of threads on this.

As far as the external valve repair or fix, I had no luck with that.
I started a thread about that a couple of years ago. Bottom line is the check valve has a cage, spring and a ball. If you remove or dislodge the cage there is not way to make sure the spring pressure is correct on re-install. At least that is my conclusion. I re-installed my external check valve. It seemed to work correctly on the bench but failed in the car. YMMV.

[Duc Hunter]

Well I can speak from experience since I just had one fail. The car has 108000+ miles on it. That tells me we should not worry too much. When it went failed made a lot of noise, esp right around 2100RPM, impossible to miss which was good as the car still got me home and to the shop. That too tells me not to worry. My mechanic, who is an old man, ex-Porsche Factory, and Brumos Race Team mechanic said he hardly ever see’s the hydraulic ones fail and that they will get you home every time safe if you are nice to the engine once it fails (keep it under 4K RPM and all that). Again, this tells me not to worry. Lasty, when I went hunting replacements (while I am in there I am doing both) the only part number that comes up is a 930 part number, which from above “is better” than the Carrera ones that is originally came with.

So I am getting 2 new hydraulic tensioner and not going to worry one bit! My only question is what else should be done while we are in there. The engine is not coming out, we will do it in the car. Hmm.....thoughts for another thread.

[Trackrash]

I assume you are referring to your '89 Carrera. FWIW "hydraulically cushioned" is what Porsche called the Carrera oil fed tensioners.

You did the right thing. As soon as you heard the noise you got it fixed. Left alone, it could have led to disaster.