Tensioner fail

[4sd911]

Had a 930 tensioner fail, engine wasn't run for a while on start up engine made a lot of noise and would not run right. Removed left cam cover and found the tensioner fully collapsed. Removed the tensioner and left it out for a few hours when I came back to look it over the piston had popped back up.

I do have a pressure fed tensioner kit what was installed before in this same engine (see old thread on noisy chains https://forums.pelicanparts.com/911-engine-rebuilding-forum/547729-chain-sound.html )

Question, do the pressure fed tensioners have any internal parts that go bad over time like O rings?

Thinking of installing the pressure fed tensioners back or I could rebuild the 930 tensioner.

[wgirardot]

If you rebuild the 930 tensioner, like I did I would like to offer some advice:
Do your due diligence on wearing eye ( and face ) protection as there are lots of powerful springs and circlips to deal with. Parts can shoot off and never be found
so be careful on disassembly, and re-assembly. John Walker has a good thread here in pelican on the re-building and bleeding of these tensioners.

Bill

[Old H2S]

Throw in a set of Stomski chain tensioners and live in peace..100$

[Dpmulvan]

[dannobee]

The Carrera tensioners don't have any internal o-rings to fail. If you do the Jerry Woods Chain Tensioner Mod and add safety wire, they're pretty much bulletproof.

Jerry Woods Carrera Tensioner Chain Gaurds. What is proper tension for chains?

Once in a great while the bleed will come out of the top. The fix is drilling two holes and adding safety wire to keep it in place.

Carrera tensioner questions

[GG Allin]

Originally Posted by Old H2S

Throw in a set of Stomski chain tensioners and live in peace..100$

Are you referring to these:

https://www.stomskiracing.com/products/911-mechanical-chain-tensioners?_pos=1&_sid=f0b48d471&_ss=r

Those can stay in the engine?

[Old H2S]

Yes, never worry again, cold starts, backfires, no oil pressure, dead check valves. Just check them once a year when you do yearly valve clearance. Chains do not stretch, they wear out and tolerance stack more and more, change your oil more = less wear.

[PeteKz]

Those make sense for a race car, because you will frequently be going into the engine, but not for a street car, unless you like pulling off the cam chain covers frequently to check them. They are not even "tensioners." They are spacers that take up slack when first installed, but do not put tension on the chain to take up wear or changing clearances due to thermal exapansion.

[Steam Driver]

Some comments on solid tensioners; been there done that.

Back in the late seventies I began running solid tensioners in my 914-6. They were there until I rebuilt the engine in the mid-eighties. They caused no real problems with the rebuild, and at that point I installed Carrera tensioners. BUT. . .

First off, they were noisy. I didn’t install them with the chains tight on a cold engine. I used a clearance; I forget what that was but I suspect the Stomski units do the same. If this the clearance isn’t there I’m sure the tension would be excessively tight on a hot engine.

When first started up from cold you could hear the chains rattling across the ramps. This went away a lot more quickly than you would think, so engine expansion quickly. And the rattle got noticeably louder the colder the temperature so even a change of 30 degrees made a difference. I never pushed the engine above 3K until the rattle was gone. This engine always seemed to “sing” more than most anyway so I didn’t notice any difference in the chain noise when hot.

I didn’t embark on this on my own. I think the idea came from Porsche guru Chuck Stoddard. At that point lots of people were trying to solve the chain tensioner problem and Stoddard was one of them.

Now the kicker, and this would still work. At Stoddard’s suggestion (I think) I made my own solid tensioners out of the stock ones merely by removing the guts (except for the piston and spring). I then drilled and tapped the boss on the side (I forget its original purpose) for a bolt to jam the piston in position after the clearance was set. Worked great.

[Dpmulvan]

Originally Posted by PeteKz

Those make sense for a race car, because you will frequently be going into the engine, but not for a street car, unless you like pulling off the cam chain covers frequently to check them. They are not even "tensioners." They are spacers that take up slack when first installed, but do not put tension on the chain to take up wear or changing clearances due to thermal exapansion.

I agree, too tight or not balanced and your putting more stress on intermediate shaft, sprocket and bearings. Porsche didn’t design them for fun.

[Old H2S]

All true..Now my counter argument, all the stock types have problems or they would not have kept changing them. You do not know when they are bad or failed. They jam up with a side ways piston and do not go in or out and wreck the shafts, sprockets, rails, bearings anyway. Why are you replacing these parts during a rebuild? Ford Modular engines copied the Porsche design and added a ratchet to the piston to keep it tight under all circumstances and the pistons still went too far out and got cocked side ways and jammed taking out the rails, sprockets et.al, hr solution was to make longer pistons, easy for me.. But a pain to install and a tight chain until break in and more wear until.. Look at the threads here on failures and results from not looking in the chain boxes anyway, catastrophic.
I am not saying the solid ones are the end all be all, they do sing at a cross over harmony RPM for a second through the time the are at that RPM. The force multiplied by the oil pressure times the piston diameter is high when the check valves are working which is for miles on a new car but the new replacements and internal components have a bad rep.
The new OEM parts used when the car was built were the best, they are gone now.
Most of the rebuilt engine problems are valve train related.
The stock systems needed a pop off valve to stop valve train shock.
If you do not look at your chains once a year when you do the valve clearance adjustment are you lazy? My point is reliability, not boulevard quietness. Have you ever heard a cold 911S start?
Stomski wants .062" gap for cold setting, too much or too little? I got no answers for you but they do solve the problem.

[PeteKz]

Tom, I think all manufacturers have had problems with chain tensioners at some point. The Carrera tensioners work reliably by my observations. Lots of Carrara engines with original tensioners in them well past 100Kmi. Beyond that, I would consider them wear replacement items.

And puling the chain covers every year is another level of PITA beyond checking the valve clearances. You have to start by removing the rear engine tin, distributor, maybe the cross bar, etc. And you might as well check the cam timing "while you're in there"...

[Old H2S]

All true, and If I could get new ones that were as good as original I would and the problem is moot. But threads here show new ones from the dealer are junk prone to failure at new. Old ones the check valves don't. A new thread last week was chains so loose sprockets were chewing into the case, all unknown with out a look see. I have checked 3 times so far in 18 months since rebuild because I trust nothing with out verification. I set my valves at .005" so they will never bind and they are the loudest sound on this build.
I know of 2 other 3.2ss engines with M1 cams that are closing in on 300 RWHP both needing a fresh rebuild for crappy tensioners and stock chains, I fight with them too over weak parts and solid tensioners bringing peace of mind.
Mine is a low power 3.2ss like yours with a 2 BBL carb for reliability because I flog my Blue Mule 350 miles one way getting to my farm in Maryland. Now how long is my 123dizzy going to hold up?

[4sd911]

I decided to just install the pressure fed tensioners without any mods

When the engine was rebuilt I made sure to use enough spacer size under the barrels to make up for machining the case and heads, the tensioners have a short distance to travel the 930 tensioners did not have enough room for the collars and the free space below them.

I should be ready to start the car in a couple of days, I've spun the engine with a remote starter switch and all sounds good.

[Dpmulvan]

Originally Posted by 4sd911

I decided to just install the pressure fed tensioners without any mods

When the engine was rebuilt I made sure to use enough spacer size under the barrels to make up for machining the case and heads, the tensioners have a short distance to travel the 930 tensioners did not have enough room for the collars and the free space below them.

I should be ready to start the car in a couple of days, I've spun the engine with a remote starter switch and all sounds good.

Not sure if the new pressure fed come with oil or not, I had some nos ones and ended up using a trigger oiler to prime them, release the grenade pin and about 10 pumps. Then put them in a vise slowly compress, put the pin back in. Install, pull pin and then a few more pumps. I believe the cap and shim mods are still available as well wouldn’t hurt to add them either.

[Dpmulvan]

From an older thread:

[PeteKz]

Dpm: Thanks for reposting that and saving me having to search for it.

John W: Thanks for writing it up initially. So the C-clip does not fit back in? I don't have a tensioner laying around to inspect, but it seems that the C-clip should fit back in and retain the piston from coming all the way out. Maybe not.

[PeteKz]

Another question about the tensioners:

As an experiment, I have been running the Quaker State 5W-30 full synthetic for the past 3000 miles. Why? because my main and rod bearing clearances are fairly tight, at .002"/.05mm, so a 5W-30 oil should be fine for the journals. It's an SP rated oil with a current additive package that has more moly to replace zinc and phosphorus. And 540 RAT rates it very highly in his wear tests.

See: https://540ratblog.wordpress.com/

I acknowledge that he recommends sticking with the manufacturer recommended viscosities in air cooled engines, typically 50 to 60 weight, because they typically do not control oil temperature as well as water-cooled engines do. Nevertheless, I'm trying it and monitoring the results. I will do an oil sample analysis soon, which will tell me whether there are higher wear metals or contaminants than normal. And I will share those.

But I bring this up here because I'm contemplating what effects, if any, thinner oil will have on the oil-fed tensioners which I have. It should allow the tensioners to move more easily against oil pressure and thinner oil in the tensioners. That may or may not be a good thing, but I haven't yet experienced strange noises at RPM up to 6500; although an engine at high RPM is making enough noise that I doubt I could hear any subtle changes in the noise level.

Any other thoughts or experience about viscosity and the tensioners?

[Dpmulvan]

Originally Posted by PeteKz

Dpm: Thanks for reposting that and saving me having to search for it.

John W: Thanks for writing it up initially. So the C-clip does not fit back in? I don't have a tensioner laying around to inspect, but it seems that the C-clip should fit back in and retain the piston from coming all the way out. Maybe not.

Yeh I couldn’t figure this out either and didn’t feel like taking them apart. Seems you need that c clip to hold in the slug on the bottom.

[stownsen914]

I recently disassembled some pressure fed tensioners to do the Woods mod. Getting those clips out wasn't a picnic. I plan to put them back in to reassemble. It appears that their purpose is to keep the piston from falling out when the tensioner is out of the engine. Perhaps it's just a convenience, as I suppose the piston is held captive once the tensioner is installed.