New Chain Tensioners

[porschecc]

I just need to know how to find out if my 911 has the new chain tensioners already installed or if i need to replace them, what is the best way to find this out

[jkh2cpu]

That's the old style. New is the pressure fed Carerra tensioners.

[MikeD]

There is also the 930 tensioner if you don't want to go pressure fed. But from the 901 part number I'd say that's not it.

[BURN-BROS]

Mike, the "narrow" turbo tensioner and the wide tensioner arm are the two things to update. Supertec sells tensioner arm upgrades if you are looking for them.

[jtsilverfox]

Those are the same ones I got back in '81 from German Precision in Boulder, CO. They said they were the latest 'Turbo' ones (at that time). Wayne's book and various comments on this forum talk about using the '930 Turbo' ones (if you're not going with the pressure fed ones), but I've never found any info on what the difference is btwn yours (mine) and the '930' (externally they look the same to me)...
cheers,
jt

[Jon B]

Originally Posted by MikeD

There is also the 930 tensioner if you don't want to go pressure fed. But from the 901 part number I'd say that's not it.

In spite of the 901 number on the support arm, that is an early, genuine Porsche 930 tensioner.

[Flat6pac]

Put on a set of guards and youre good to go.
Bruce

[motogman]

I have been looking at tensioner threads and have a few questions...

I recall seeing a thread on rebuilding pensioners that had good pictures of one apart but I can't find it now. Can anyone provide a link to a thread w pictures?

It seems that there was a time when rebuild kits were not available - are they now available?

Thanks in advance...

[jkh2cpu]

You can get them here, but it's not recommended. Flat6pac had
a good suggestion: chain guards. Back in 79 I heard the chain
death rattle while in McDonald's (Strange how one remembers
exactly when and where.) I was broke with a young family while
restoring an old farm house (yes, that really happens), so I settled
on some mechanical chain tensioners. I set the gap at 2 mm, and
was good to for for another 40 K miles before I upgraded. Stomski
Racing will sell you a pair like this for about 90 bucks.

Myself, I'd go for the Carrera Tensioners, but these will do in a pinch
or a tight budget.

[Henry Schmidt]

The difference between early 901 tensioners and late 930 tensioners is the width of the boss that indexes the tensioner arm. Late 930 tensioners have a narrow boss that allows for a wide tensioner arm. Porsche superseded all 911 engines to the wide tensioner arm in 1984. The main cause of tensioner failure is the arm binding on the pivot shaft. The wide tensioner arm minimizes this issue.
We make a wide tensioner arm that also minimizes the twisting that creates the galling that binds the arm to the shaft. Any effort create a lasting tensioner without replacing the arm is a fools errand.

[Trackrash]

All good info here. However, the reason why these tensioners "fail" is due to the loss of oil in the tensioner over time. At the top of the tensioner is a "reservoir" of oil that does not last for ever.

Refill the tensioner with oil and make sure it is bled, add the safety collar and upgrade the arm and you are good to go. I have rebuilt my original '71 tensioners two or three times over the years and I have had no failures

BTW. Henry can you give me a source for your idler arms?

I searched your site and here at Pelican with no luck.

Thanks,

[Jon B]

Originally Posted by Henry Schmidt

The difference between early 901 tensioners and late 930 tensioners is the width of the boss that indexes the tensioner arm. Late 930 tensioners have a narrow boss that allows for a wide tensioner arm. Porsche superseded all 911 engines to the wide tensioner arm in 1984.

Henry, I believe Porsche introduced the wide tensioner arm (idler arm) in 1980 for all models, and narrowed the 930 tensioner boss at that time.
The 930 tensioner was introduced with the '76 Turbo Carrera, having both internal & external improvements from previous versions, making it more reliable.
The 930 tensioner came in both wide boss (930.105.049.00) and narrow boss (930.105.053.00) versions. Earlier versions still had 901 casting numbers on their support arms.
The pressure-fed Carrera tensioner was introduced with the 1984 model year engines.




Factory diagrams compare earlier 911 tensioner internals (left) with 930 tensioner internals (right)...




A progression of chain tensioners, from model year 1965 to 1983. The last two pictured are 930 tensioners...

[Henry Schmidt]

Thanks for the clarification John B. This makes it even clearer that the wide arm was introduced to address a problem with tensioner longevity even before the pressure fed tensioner.
The design of the tension is such that, when functioning properly, it is self priming and will refill itself with oil as necessary. It should never "run out" of oil.
Heat (especially in mid 70s 2.7) and tensioner (idler) arm binding are the major reasons for premature tensioner failure.


Supertec tensioner arms (use by many of the worlds best engine builders) are available directly from Supertec or Ken @ 911 Vintage Parts. 760-731-4911
info@911vintageparts.com
For those purists amongst us that would prefer factory wide tensioner arms, they have good used versions of those as well.
Email or call