There's a common misconception that "930 tensioners" are the same as "pressure-fed tensioners". Not so.

So-called 930 tensioners (930.105.053.00 or 04) are an improved version of the original chain tensioners with a self-contained reservoir of oil. They are standalone, only receiving add'l oil as needed from oil splash as occurs in the chain box area.
http://forums.pelicanparts.com/uploa...1469860864.jpg


Pressure-fed tensioners (930.105.058.03) are fed engine oil under pressure from the engine's lubrication system. The kit contains two of these tensioners along with accompanying external oil lines and chain box covers.
http://forums.pelicanparts.com/uploa...1469860886.jpg

Either choice is expensive. Hope this helps.

Sherwood

You are correct.............
 

Bruce,

When I installed the newly purchased Carrera hydraulic tensioners, I thought it would be an easy cruise to victory lap. And I could almost smell the joy of success. But the euphoria was short lived. First, the newly installed tensioner at the right side bank exhibited failure or collapsed by just cranking the engine for oil lubrication. I was not even running the motor. Removed the tensioner and tested. Confirmed defective when I could compressed the piston by hand.

Replaced it with a used known good unit from another engine. Test cranking the engine produced no abnormal noise. Left side still has the newly purchased tensioner and right side has the a used tensioner. Repeated the cranking cycle several times and was satisfied with the result. Next is to run the engine and observe.

The first attempt was not good. Turned off the engine and took a deep breath. Why? Tried to start again the engine and the knocking and rattling noise was there again. Not another bad tensioner? Removed the chain housing cover and inspected the tensioner. It was not easy to tell if the tensioner was bad so I removed and tested it on the bench. The tensioner has also failed this time because I could compressed it by hand.

So I asked myself if it was really a bad tensioner that was causing this abnormally loud engine rattle (knock) noise generated when you start the engine? Cranking the engine with the FP and CDI disabled seemed to be OK but not when you run the engine.

Next, I installed a second good used tensioner at the left side. Both sides now have used tensioners which were tested and showed very hard resistance to compression. With two (2) good tensioners, everything should be OK (?). Turned the ignition switch and kept my ears close to the engine to hear anything. Result: loud engine noise or rattle.

Back to square one:
When you cranked the engine with the ignition disabled, no abnormal knocking sound. However, with the ignition ON and the engine starts running it produces this loud rattling noise.

As a side test, I installed a mechanical tensioner at the left side and left the used tensioner at the right side and run the engine for a couple of seconds. Same annoying loud noise. Maybe it was coincidental that the tensioner/s was bad and the root cause of the abnormal sound is still undetermined or unkown (?).

What do I do next? There is something evidently wrong in the engine and I do not know what to look for. So I am back again from the beginning of my search to diagnose the root cause of this problem.

Why does the engine sound normal when you crank the engine (ignition disabled)? The engine speed is much less without ignition compared to a running engine. What mechanical part/s of the engine is causing this noise? I need help and guidance to solve this nagging problem. Thanks to everyone.

Tony

Combustion can cause piston rattles if the bore is out of spec... it won't show while cranking. Same for rod bearings as they're in the stack beneath the combustion loads.

Are you certain it's not something like bendix from the starter not retracting?

Combustion pressure would tend to show wear in big and little ends that might not be evident just spinning the engine?

tony... if you are wanting to get this on the road sooner than later, no offense intended here, take the eng on its stand to mark and let him listen to it... he does have a lot more yrs of porsche engine sounds that are good and bad than you I believe...
I understand you wanting to conquer this yourself, but, if you want the car on the road soon, get more experienced input and let us know how it goes...
I am hoping it is nothing requiring a teardown, but prepare for the worst and hope for the best... good luck...!!

Making a list of probable culprit/s for the next tear down........
 

Things to test and verify:

---Connecting rods bearing (big & small ends).
---Cylinder bore (out of spec.)

Please continue to suggest and share your thoughts. I will consider each and everyone's suggestion without bias. I have plenty of time to digest these suggestions during my extended family vacation in Carmel, CA next week. After my return back home, the inevitable engine tear down has to be done. Thanks.

Tony

Begin diagnosis with a compression/leak down test. If the engine runs w/o endangering further damage, run engine while shorting (disconnecting each spark plug wire) while listening to the engine. If noise reduces on a disconnected cylinder, suspect the rod bearing on that cylinder. If not, could be a main bearing, that's about it for active engine diagnosis. Thereafter, engine parts must be removed for further inspection. Ok thus far?

Remove the distributor and inspect. Remove valve and chain box covers and take a look. Check tightness of threaded fasteners, rotate engine manually while observing all moving parts.

Remove drivetrain and inspect clutch/flywheel area. Inspect cooling fan and alternator Remove flywheel and inspect. If all appears ok up to this point, engine comes apart while inspecting pieces. Eventually, it'll be apparent. The slippery slope is yours.

Sherwood

Professional Porsche shops......
 

Tweaks,

I hear you and I know Mark B. personally for more than 20 years. His phone number and email are in my contact list. BTW, I don't want to conquer this problem by myself or I would not be in this forum seeking help and advise. There are several well respected shops near by and would consider them too. I will be leaving for CA in a few days and would be away for several weeks and will make some calls to these guys including Mark B. Thanks.

Tony

Over-stretched timing chain........
 

I just noticed tonight that the Carrera hydraulic tensioner in bank 1-2-3 (for my problematic engine) has the piston almost out all the way. Preliminary measurements (roughly) showed just about 1 or 2 mm for full extension. Will take pictures tomorrow.

In the picture (7-19) in Wayne's Rebuild book, you could see the 'step' about half "in". And mine is out a lot. I need to remove the muffler to get a good picture and I am too exhausted and ready to go to bed. See you tomorrow.

Tony

I once noticed that the top of the idler arm, against which the chain tensioner piston presses, was about hitting the chain housing. Why, I wondered?

Chain stretch? Not that much, I thought. Sprocket wear? Couldn't make that much difference.

Took the idler off. It was cracked! And it's a forging, I am pretty sure. But cracked, which distorted it.

Not likely to be the cause of your issues, but the left side idler (if my mental picture is still correct)is up close to the top of the housing, and the chain jumps around quite a bit, good tensioners or not.

Walt

Over stretched timing chain .........
 

Walt,

While I could not ignore the connecting rods (big and small ends), the stretched timing chain has caught my attention too. At this point, I am not certain if the jumping motion of the idler gear/s is producing the loud and heavy rattle/knocking sound from the engine or not because the abnormal noise is only observed when the engine is running (higher RPM) compared to cranking the engine using the starter. I am trying my best to sort and identify these likely culprits before the engine tear down.

It the culprit/s could be determined or diagnosed correctly before an engine tear down would be ideal. It would be pitiful to find out that I could have done and discovered the root cause of this nagging problem without a complete engine tear down. And an engine tear down is mostly to happen if I failed to identify it sooner.

I will bring the engine installed on the engine test stand to a couple of professional Porsche shops to take a final look before tearing it apart. Anyone have an idea or suggestion please post it or PM me. Thanks.

Tony

Can you run the engine with the timing covers removed?

I'm kind of loosing track of what you reused or replaced, so here is my input relative to your last post:

Pictures from my rebuild should help you assess chain and sprocket wear effects.

This is the gap between the idler and the chain housing after rebuild:
http://forums.pelicanparts.com/uploa...1469978714.jpg

New Cam chains
New Intermediate shaft sprockets
New idler sprockets
New Cam Sprockets
New chain ramps
REUSED LHS idler
REUSED LHS tensioner

This is what my 135,000 mile engine looked like at teardown:
http://forums.pelicanparts.com/uploa...1469978342.jpg

It doesn't take more than a few moments before you see just how much different the position of the idler arms and extension of the SAME tensioner between new and old.

For Completeness this is the RHS after rebuild:

http://forums.pelicanparts.com/uploa...1469979147.jpg

New Cam chains
New Intermediate shaft sprockets
New Idler sprockets
New Cam sprockets
New chain ramps
NEW RHS idler
NEW RHS Tensioner

I had to replace the RHS idler arm because the bushings were worn too much and no one makes replacement bushings. I also had to replace the RHS tensioner after only 38 miles due to knocking sound on start up. I'd go away after some seconds, but obviously a bad thing.

I now use a heavy tie wrap to hold the chain tight when I swap between the mechanical adjuster and hydraulic tensioner. It prevents the deadly chain jump if the idler arm is allowed to drop.

Here is the 135,000 mile teardown:

http://forums.pelicanparts.com/uploa...1469979418.jpg


Also note: My observation is the shaft that the idler arm rides on must be absolutely smooth. Over time the worn copper gets stuck on the shaft. It will cause binding.

It must be polished smooth so that all evidence of copper is gone. I used 3000 grit wet polishing paper.

I also think, IMHO, that idler shaft binding is one of the prime reasons for tensioners not working properly. There is a lot of load on that shaft, and any material deposits on that shaft will defeat the oil layers ability to let the idler rotate smoothly.

For completeness
Cases were not machined
Cylinders replaced, but same height class
.25mm base gasket
Heads resurfaced .008".
Original cam towers

So I can say my cams were .008" closer to the crankshaft

Chain housing removed.......
 

James,

I have been cranking the engine without the chain housing covers repeatedly with the ignition disabled. But once I turned the engine with the ignition connected, the knocking/rattling noise was very alarming. And quickly stopped the engine.

Tony

The pictures I needed.......
 

Mike,

Ignore my request in your other thread. I did not read this thread before reading your other post about cam timing. These are what I wanted to ask you. Thanks.

Tony

What would you do?????
 

Mike,

Take a look at the pictures below.

http://forums.pelicanparts.com/uploa...1469988642.jpg

http://forums.pelicanparts.com/uploa...1469988664.jpg

In the first picture, you will see how close the idler gear arm to the chain house and the amount of the piston protruding. In the second picture is a fully released tensioner. A rough measurement gave me about 2 mm for the installed tensioner to full extension. The piston in your engine showed a much less exposed piston length.

The engine was delivered to my house in several boxes by the owner (PP member) after two (2) auto shops failed to finish the job. I accepted the job because I like the challenge of getting this engine running again. I knew this would be more difficult and challenging but never expected it to be a nightmare.

Would it be prudent to replace the old timing chains and sprockets now or start the inevitable engine tear down? And start all over again? What would you do if you were in my shoes? Thanks.

Tony

I think the chains are stretched too much. More than mine.

As a former motorcycle rider, I would never use old sprockets with a new drive chain. So I would replace all of the sprockets.

If the noise is caused by an overextended tensioner (driver side), the idler arm might be too close to the chain box/housing. Look for signs of the idler arm hitting the housing.

Chains don't actually "stretch". However the interconnecting links and pins can wear which results in a longer chain. If this is the case, chain sprockets will also show abnormal wear. Remove, inspect, measure and replace as needed.

As for the other chain parts (sprockets, idlers, chain ramps, etc., inspect and compare with new and/or good components before shelling out more $$ for add'l good parts.

Do you have any engine history? Here's one possibility:
The builder could have machined the typical engine parts (including crankcase spigots, cylinders, cylinder heads) to a total amount that reduces the valve train "stack", the above parts between the camshaft and crankshaft encompassed by the chain. Remember that any machining of the above parts affects the stack as well as the position of the camshaft within the opening of the chain housing (it must remain centered). If significant material is removed, the chain housing mounting surface must also be machined an equivalent amount to re-center the cam, otherwise the cam seal will distort and leak at that location.

Back to the chain. In addition, since the stack is shorter due to removed material (narrower engine), the chain is now effectively longer, thus the extended stroke of the tensioner piston/rod to take up the slack. One strategy to mitigate this is to install a larger Idler gear to take up the excess. Bruce Anderson's Performance Handbook shows the opposite condition; a wider engine and thus the need to increase the effective chain length via a smaller idler sprocket (page 192).

During inspection, you or the builder will discover the issue and what is needed to correct it.

Hope this helps,
Sherwood

Tony

Since I did have to make the call on my engine, I new that splitting the case meant I'd do the chain. After looking at the sprockets I decided I would just spend the money and replace all the sprockets. They were worn.

Overall I spent 2x more than I expected on the rebuild. I found many more parts worn out than I first guessed. If it bothered me it was replaced or repaired. Some stuff I inspected and found within limits and I reused then. The left hand idler was good. But the right hand wasn't hence I only did the RHS.

i would imagine a nearly fully extended tensioner is not working within its normal range. And may not be able to damp out the pulsations.

Yes chains wear out with the sprockets and when you adjust the axel, it is as if the chain is longer. We call that a stretched chain.

Which supports the need to replace the sprockets with a new chain.