I noticed that there is a kit for rebuilding the early chain tensioners. At $27. it sounds like a deal over the $180. for a new one. Anyone ever had any experience with this? In the book it says to only assemble the first part then take it to the dealer so they can use tool #bla bla, for the final assembly and bleeding.

Anyone???
Mike D.

Bleeding? The early ones are basically just a spring. By bleeding, do they mean a blood sacrifice? I can believe that.

I was planning on buying the same kits for mine. 2x$27 seems a much better price than buying the hydraulic setup.

I dunno James... seems to me $180 a pop ain't so bad once you get a few $$grand$$ crammed up the exhaust pipe.




M

Well, if you read Wayne's engine rebuild book, his approach is "Why Skimp?". He also sells the parts to rebuild an engine...

If it's $27 to rebuild each tensioner, and I do it every $100,000 miles, then I can get many many hundreds of thousands of miles out of my car before a hydraulic system makes sense.

And then there's the time value of money....

You can bleed the early chain tensioners with a paper clip, or piece of spring wire...........

You kind of have to burp the tensioner, and get all the air out of it.


I have the Porsche shop manual that shows the procedure..... Ill scan it if I cant convince you to save up and get the later hydraulic style tensioners.

If you dont get the carrera tensioners, at least get some new tensioners, The bore in the old ones could be a bit worn.. and just be trouble down the line....

Upgrade to the new style, its the right thing to do when doing a rebuild..

I doubt any Porsche dealer will know how to bleed them..

OK, so I took the jamed one apart, sprooinngg, parts everywhere. I found all the pieces. Nothing looked damaged but I thought I would see if I could put it back together before getting the rebuild kit, I figure If I can then I'll get the rebuild kit and do it again.

Well, It takes three hands and probably a special tool to get the retaining ring back in place. and there are two of them!

So I called TRE, "nope, we don't rebuild them" - So I call Rusnak Porsche in Pasadena, "Rebuild What? Really, I don't think we do that, never heard of it, call back and ask a tech." - Uh, I am calling...

I would rather have the Carrera set up. But, my engine is a Frankenstien of parts and I have no idea what the displacement is or what the cams are. I would like to get it in the car, running, and have the carbs dyno tuned. Once all the bugs are worked out and I'm sure the engine is good I'll move forward with Carrera tensioners.

And I'll see you all in June!
-Mike D.

I've spent some time rootin' around the front end of the 911 motor. Found some interesting stuff (plus a bit of reading)leads me to belive:

Early (all, actually ) magnesium chain housings seem to have a limited life. The tensioner pivot wears unevenly resulting in a step of the shaft. The "narrow foot" chain sprocket arm is responsible for this. Binding can loosen the pivot shaft in the housing bore.

All this nastyness causes (again, an opinion):

The shaft to wander....leaking oil is the *least* of the problems. It tends to wander towards the cylinders where it gets stuck...if you're lucky. Left to it's own devices, it can pop out of the chain cover (which supports the front end of the shaft) and gets loose in the werks....loss of chain tension, valbes into pistons.....the gud news is the motor stops spinning pretty quick.
I have seen 3 sets of mag (2.4L & 2.7 L)housings. All of them were hosed in one way or another.

More common is tensioner failure due to binding/vibration.


My solution was at the Porsche parts store:
New aluminum (3.0L) chain housings.
New "wide foot" (with bronze bushings) pivots.
New pressurized tensioner kit.
New sprocket assys.

This stuff is not cheep....800-1000 bucks.....plus my .02.

It's been a while since I've done a total 911 engine rebuild, but I have done 3, a couple of 2.4 and a 2.0.
All of them the tensioners were junk.

Get the new upgraded units at least, the best is to bend over and get the hydro's.

I knew that pic thing would come up sooner or later. So here you go.

Mechanical Tensioner all laid out. The lower half of the piston is hollow. All the little pieces fit up in there.

Here is the piston and ball valve that you have to bleed before installing the circlip. I used a C clamp in a vise to hold it in place and I still could not get the circlip in place.

And here is the Porsche Factory rebuild Kit that nobody knows about or want to use. It comes with everything except the main spring, the piston, the top guide (there is a new oil o ring for this part) and the top spring retainer.

This one will be returned (that is why the bags are not opened), I've already got a good one from a friend. Thanks Alex.

the kit has a part number, as shown in the factory parts manual.
i bought a pair from Performance Products - they'd heard of them and had them in stock.

when i got mine - the little plastic bags were unsealed and empty. -most- of the teeny parts were rattling around loose in the big box. i called to get replacements, and they sent me another whole kit - and its plastic baggies were unsealed and empty - and the big box was missing a couple pf teeny parts. fortunately, different teeny parts than the one it was supposed to provide spares for... (actually, IIRC, i'm still missing one small copper sealing ring, but i have no issues reusing that.)

there are many who feel uprating to the latest hydraulic (930 part number) tensioners (and all that entails...) is the way to go - the pressure-fed tensioners have 'the hype' but they have failure modes too... if you're in there for any reason, by all means add the set of tensioner guards so you won't lose the engine if the tensioner should fail. v-e-r-y cheap insurance.

BTW - the pictures here are of a hydraulic tensioner. there -are- "mechanical" tensioners that are just springs - no hydraulic damping at all. these are not thought of well although there may be racing engines that operate at very consistent and high rev ranges where they work okay...

Yeah Mike! Thanks for the pics.



My motor has some sort of hydraulic tensioners (as evidenced by the oil lines going into the timing chain covers). And Larry Lee's db produced an old advertisement stating it had "Carrera chain tensioners". I've heard this tensioner gaurds statement before (thanks Rich). Anybody have pictures of those? Where's Brad? I know he has to have pics somewhere.

i got mine from Pelican, lots of places have them for comparable prices. IIRC, mine did not come with the 3mm guage shown in the picture but i didn't sweat it, 'cause i have other ways of measuring 1/8" ...

as long as i'm editing ... for completeness:

you don't use the tensioner guards with the pressure-fed ("Carrera") tensioners. just with the hydraulic-damped 'early-style' tensioners.

Jerry Woods was developing a travel-limiting protection device for the pressure-fed tensioners, but i have no idea if they've been brought to market. that's the irony - even with 40 years of development, even the pressure-fed tensioners have a sudden, catastrophic failure mode ...

Thanks Rich

Anyone have pictures of these things installed?

there's one on the pictured tensioner. that little hat-thing on the shaft.

they aren't for pressure-fed tensioners tho ...

I should clarify. Pictures of the tensioners/gaurds/whatever installed on a motor. I'm not intimately familiar with what everything looks like behind the timing covers.

Now I'm confused (not the first time). You're saying that these tensioner gaurds in your pics are for non-hydraulic tensioners? You original statement made me think that they were for hydraulic tensioners.

in-service they look just like normal tensioners - it's just a little travel-limiting collar that clamps down on the shaft. i don't have any pictures of 911 chain, ramp, and tensioner layout here, but they're in every 911 book. there is no magic, it's just a tiny part that keeps the tensioner piston from compressing too much. 1/8" is all the travel it needs to compensate for the engine's thermal expansion.

they are for conventional hydraulic tensioners.

not "mechanical" tensioners (just springs...) that came out in the mid-70's when the original tensioner failures started happening a lot - you may fine these on the occasional race engine now, i don't think anybody uses them on street cars any more...

they are also NOT for pressure-fed ("Carrera") tensioners. those work on similar principles but with completely different internal parts. Jerry Woods had a device to work on those - but the shaft clamps isn't it.

Don't yell at me man! I'm sick. This head cold isn't helping me today.

I *think* I understand. Thanks for your patience Rich.

Now, does anyone have any further info on this tidbit?

not trying to yell, just trying to be very clear. it -is- confusing, because over the years people have got sloppy with their terminology. i -think- Anderson-II covers the history of the tensioner issue.

so - which tidbit were you asking about ?

the failure mode ? the last thing i remember seeing/hearing/readins is that "sometimes" they just fail, usually immediately after installation (first startup). i know this was covered at the 911 Rebuild class but i didn't really pay attention because i don't believe the pressure-fed tensioners are needed and i never plan to own a car new enough to have them. in some circles wity're viewed as a "solution without a problem". yes, i know it's what all the current 911 guys recommend when they talk about the issue in Panorama.

i'm not going to talk about JW's solution, because while he didn't exactly swear us to secrecy and make us sign non-disclosure agreements, i thought it was a pretty clever answer to the problem and he ought to get first crack at marketing the product. i will say that it's not an external fix - you must disassemble / rebuild the tensioner (which pressure-fed tensioners require sooner or later, just like the conventional hydraulically-damped tensioners ...)

obviously - i wouldn't remove them from an engine that already has them, either from the factory in the case of newer engines, or in the event of a prior owner's 'update.' i don't think they're bad, just unnecessary.

Thanks for the info on the failure mode. The tidbit I was asking about was described here:


So, is this something Jerry Woods sells to the end consumer then? Or does it requires his organization doing the work? In-house only type thing?

These blocks replace the tensioners while your setting up the cam timing.

he was talking about it being a product, in the same vein that the tensioner guard is a product. i have no idea if he's moved forward on that.

"someone" should contact his company to see if there is a current status. this isn't a good time for me (thrashing a product out that shouldda been out end of December...) and i'm not a potential customer anyway. if he said, "yes, i've got 'em and they're $50/pr" i'm not going to say "cool, send me a set."

what you'd be asking about is a "chain tensioner travel limiter for pressure-fed tensioners."

they are fundamentally simple and could be made by anyone with simple machine tools, but i don't have any of the measurement data. who knows - it might be the kind of thing he'd subcontract the fabrication to Mueller (for example)...

Are they similar to the ones for the mechanical/hydraulic?



James

i'm sorry, "they" which what ?

IMO, "mechanical" should not be used in conjunction with 'chain tensioner' unless you're describing a non-factory replacement part which is JUST a spring. i wish i could find a picture of one of those abominations... but they're just spring cartridges that install into the body of a hydraulic tensioner (like the picture RedBeard and i included).

Porsche has *always* used hydraulic chain tensioners. they changed a few times over the years but they are *always* hydraulically damped.

the pressure-fed "Carrera" chain tensioner is hydraulic but it obtains oil from the gallery instead of relying solely on an internal reservoir.

the picture RedBeard posted of a factory hydraulically damped chain tensioner is shown with a "tensioner guard" installed.

the clamp-on-the shaft tensioner guards work with the factory hydraulic chain tensioners. they do not work with the pressure-fed "Carrera" tensioners...

i am trying to be as clear as possible about this confusing topic because these parts are hard to work with considering the very substantial spring tensions involved. the car is out of service once you get into the chain ramp area, and if you screw up the tensioner rebuild/install/whatever your valves will get (too) friendly with your pistons and you will be unhappy. and poor.

there are little holder gizmos (just a very strong 'C' shaped metal piece) that hold the compressed tensioner after it's been compressed in a vise or an arbor press until it can be installed in the engine.

so if i am not being clear on any of this, please let me know exactly what is not clear and i'll try to explain it more clearly. frankly - if you have a 6-cylinder car, you should be reading up on this topic in Bruce Anderson's and Pelican Wayne's books...

----------

okay - that said, i recognize the possibility that that last question was posted to yank my chain a little, in which case i can take the joke as well as anyone...

No chain yanking here. I yank my own chain and only if necessary....

The "they" i was referring to (are you Bill Clinton or something) was the new product referred to in the previous posts.

And I used the word mechanical to describe the "Spring Loaded" chain tensioner in contrast to the "Carrera Pressure-Fed" chain tensioner. I've never heard the "Spring Loaded" ones referred to as "hydraulic". I do find them called "mechanical spring-loaded tensioners". And I find the "Carrera" ones described as "newly designed tensioner...driven both hydraulically by oil pressure and also by a standard mechanical spring." Later in the update article, the late style are referred to as "hydraulic chain tensioners"

Tensioner update article

James

aha. well. i think that article is designed, in part, to sell conversion kits... it glosses over several/many points about the "early" tensioners and IMO goes out of its way to make them appear inferior. in fact, many of the problems attributed to early tensioner failures were caused by pivot issues. updating to all the latest stuff - which as JP pointed out is not trivial or cheap - takes advantage of the hard lessons it took Porsche 30 years to learn.

all the Porsche chain tensioners have very powerful springs, and are hydraulically damped. 911's make such low oil pressure at hot idle that we should hope they aren't depending on that to keep the chains tight :-) ... -mostly- the pressure-fed tensioners connect to the gallery to make sure the reservoirs never run out of oil.

the travel-limiting device for the pressure-fed tensioners is not a shaft collar - it is internal.

a Slick Willie i'm not, but i was a journalism major and i've done some technical writing. there is so much confusion in this area caused by imprecise use of the terms "mechanical" and "hydraulic" (as if they were mutually exclusive in a Porsche factory chain tensioner context, which they are not) that i'm trying to be very clear about what parts are and are not involved.