Early 911 question - Is the hydraulic tensioner update a neccessity on a 2.4L?

[Jim Richards]

Early car folks, I'm talking to a seller of a '72T and asked if the hydraulic tensioner update was done. His response was that it has the stock tensioners, which on the 2.4L are considered adequate. He further stated that this was an issue starting with the 2.7's.

Now, I'm under the impression that this is incorrect; however, I am still wet behind the ears, especially with early cars, and look for expert guidance on this. Thanks in advance for your help!

[pwd72s]

Dear "wet behind the ears", Regardless of year, the '84 Carrera tensioner upgrade is desireable to see on ANY used air cooled 911 you may be considering buying. Abby

[Jay Auskin]

I agree with the fact that the upgrade is desireable for any year.

I disagree with the seller that this was only needed starting with the 2.7.

Now further, I remember a post a few weeks back with a question/statement (don't think it was answered) that the '72 2.4L T engine was actually the only non-interference Porsche engine made!?!?

I agree that regardless, it is good to do on this engine, because serious damage or not, you're still stuck with an engine needing repair if the mechanical tensioners fail. But I guess I'm still wondering about the statement I read with the '72 2.4L "T" motor.

[911pcars]

Realizing that the pressure-fed tensioners are the most desireable, there's also a sizeable cost factor to install these, especially if done by your favorite wrench.

A second-best option, perhaps perfectly adequate for many, is the following:

- Latest version hydraulic tensioner (so-called "Turbo" tensioners)
- Mechanical stop kit in case of seal failure on the above
- '81 double bushing idler arms

I believe Roland Kunz suggested the above tensioners be replaced every 60,000 mi. or so. Probably a good idea just to be sure. In addition, all 911s should have the proper hard plastic chain guides (black and brown) installed.

Jim,
This 30 year old 2.4 most likely has had the tensioners replaced once upon a time. Does he have any paperwork? If they're original (highly unlikely) or replacements with high mileage, they're candidates for replacement now. I wouldn't turn down an otherwise nice car just because it doesn't have the PF tensioners. Good tensioners are an issue for all 911 engines; it's not really a displacement issue.

Sherwood Lee
http://members.rennlist.org/911pcars

[Wayne 962]

It's dumb-ass talk from a guy who's trying to sell you a car. The smart answer would have been 'I don't know' instead of making up an untrue answer.

If he doesn't know what he's talking about here, then who knows what else he's done with the car, thinking that he knew best.

I typically avoid cars with owners who are clueless, yet spout incorrect information. It shows that they think they know how to care for the car, when they actually don't.

-Wayne

[Zendalar]

"question/statement (don't think it was answered) that the '72 2.4L T engine was actually the only non-interference Porsche engine made!?!? "


Hmmh, so you are saying that 72 2.4T is the only engine where the pistons won't hit valves in case of a broken or misplaced chain, or collapsed tensioner??

[Jim Richards]

Yeah, what's that about?

[Jim Richards]

A second-best option, perhaps perfectly adequate for many, is the following:

- Latest version hydraulic tensioner (so-called "Turbo" tensioners)
- Mechanical stop kit in case of seal failure on the above
- '81 double bushing idler arms

I believe Roland Kunz suggested the above tensioners be replaced every 60,000 mi. or so. Probably a good idea just to be sure. In addition, all 911s should have the proper hard plastic chain guides (black and brown) installed.

Anyone have the part numbers for the parts Sherwood mentioned above? I'm hoping the seller has records showing a prior tensioner replacement. I imagine the records may only show the part mumbers.

If there's nothing to show that the tensioners have been replaced, I suppose I need to factor this into the negotiations.

Also, I'm very curious about the comment about the 2.4L engine being a "non-interference engine". Any ideas about what that means and the implications, if any, to my tensioner concerns? Thanks!

[rvanderpyl]

A non interference engine is one in which the valve lift and piston configuration is such that if a timing chain broke there is no chance that a piston will come into contact with a valve even if the valve happens to be wide open at the time. As far as I know all 911 engines are all interference designs, I think that the early 928 engines were not. It's really a function of how radical the cam is, and how much cut-out may exist in the piston top.

If it was a necessity it wouldn't run. I run mechanical tensioners with the stops.

[dtw]

Jim,
There is a visual dead giveaway if the car does have pressure-fed tensioners. Look at the cam tower oil lines which run horizontally from the case (center) out to the cam towers (to the left and right sides of the engine). If there are feeder lines on each cam tower line, running vertically from around the center of the cam tower line down to the chain case covers, then the car is equipped with pressure-fed tensioners. Look at the left side of this pic:
http://www.pelicanparts.com/MotorCity/WintersRS/garage/Photos/DSC00202.jpg
(I'd already removed the line on the right side so disregard that).

Are you comfortable doing a bit of wrenching? This is an easy-to-moderate difficulty project that will save you quite a bit of money if you do it yourself.

Dave

[Jim Richards]

Hi Dave,

The seller says it doesn't have pressure fed tensioners and that they aren't necessary on the 2.4L (obviously some debate on that). If I do buy the car, I will probably DiY this upgrade unless the seller's records indicate that the tensioners have been recently replaced with the 930 style hydraulic tensioners. There's some other details that I'm trying to get a handle on (e.g. ramps, stops).

[barlowdo]

Why are the pressure fed tensioners considered so much an improvent over the mechanical stop tensioners ?

It just seems that if you compare apples with apples. How can one expect a mechanism of increased complexity to be more reliable ?

Have pressure fed tensioners actually got enough miles/hours/years on them to prove that they are infact more reliable than the mechanical stop tensioners ?

This is a question I have been wondering for awhile now.

-Don

[Jim Richards]

I have heard (or believe I heard) that the mechanical tensioners are harder on the chains and maybe also the top end. They also need to be periodically adjusted.

[911pcars]

Perhaps some explanation so these terms don't become synonymous:

"Mechanical stop tensioner"
These are factory hydraulic tensioners (self-contained, not pressure-fed) with an aftermarket clamp/collar around the piston rod to prevent total collapse in case of a seal failure. This maintains some tension on the chain to prevent a tooth from skipping a sprocket which results in you know what. A somewhat louder chain slapping noise is an indication you'd better fix something. The somewhat fragile mech. stop has a limited life span in the collapsed mode. You don't want to know what happens when it becomes pounded by the chain.

"Mechanical tensioner"
This is a tensioner that uses purely mechanical methods (thread and lock nut, etc.) to remove chain slack. Many argue an engine w/mech. tensioners has no provision for heat expansion or wear after initial adjustment. However, some race engine builders have used them to simplify the mechanicals. Many use them to initially adjust the camshaft timing before installing the proper tensioners.

Sherwood Lee
http://members.rennlist.org/911pcars

[Sunroof]

I have oil-fed tensioners in my 2.4 for my 1973.5T. And you know what? Takes Wayne's advise.....................walk away from this nut.



regards
Bob

[Bob Spindel]

This is a rant, because the subject has always bugged me...

I don't think anyone will argue that the updated pressure fed tensioners are not better than the older (in this case 30-year older) self-contained tensioners. Most (not always all) updates tend to be improvements. But to me the endless discussuion about the pressure fed tensioners has always seemed overkill. The old ones aren't that bad. There are many, many thousands of 911's working perfectly with the old tensioners. If you add the mechanical safety stops (not mechanical tensioners as has been pointed out) you've pretty much got a bullet proof system. Indeed, it's more robust than the pressure fed tensioners without the stops. The pressure fed tensioners can fail too, you know. The stops, by the way, cost about $25 and can be installed in a few hours with simple tools. The tensioners cost $500, and goodness knows what shops charge these days to install them.`

I've rebuilt a (small) number of early 911 engines with the old tensioners, and in every case the ones I've removed have been in good shape. For the sake of a complete rebuild I've always rebuilt these too--a few o-rings, a spring, and perhaps a new ball-bearing--and I've installed the safety stops. But in every case, and some of these cars have had over 200K miles on them, the interior parts of the tensioner were okay. The o-rings after 30 years were hard, and stood replacing, but in no case had the seals lost integrity.

I think there's a lot of hype about the pressure fed tensioners, probably fostered by the add-on industry (along with pop-off valves).

On the issue of whether or not to buy the car because the seller doesn't know what he's talking about, well that's another subject. If you know, and he doesn't, you can often do very well. If you don't know, and he does, you can get into trouble. If neither of you know, well, then it's anybody's guess. In that case, I'd go along with Wayne's advice.

[Vipergrün]

Originally posted by Bob Spindel

I think there's a lot of hype about the pressure fed tensioners, probably fostered by the add-on industry (along with pop-off valves).

Bob, it not like these are parts are made by the doods who make the aftermarket stuff for the ricer Hondas, etc. There is actually a valid reason behind installing both of these, just ask anyone who has blown a CIS airbox, or had tensioners fail. Some folks are not at all mechanically inclined and cannot detect an iminant failure of a tensioner. These provide forms of insurance.

Here is the service bulletin info on the tensioner issue;

158401 MAY 84 Hydraulic Chain Tensioner - Installation For Retrofit


cheers
-Brad
80SC with aforementioned upgrades