Never ending problem for the 13th engine rebuild (very long post)......

[Alan L]

Tony, Is it worth fitting your mechanical tensioners (seen them in earlier pics) and try running the engine briefly. You would need to catch the oil feed in a couple of small containers. I would tension the crap out of the chain, lock it in place, bolt the housing cover on and give it a shot. If the problem goes away you know you are on the right track.
Or have I missed something? I am presuming you can run the engine with those tensioners.
Regards
Alan

[boyt911sc]

Originally Posted by Alan L

Tony, Is it worth fitting your mechanical tensioners (seen them in earlier pics) and try running the engine briefly. You would need to catch the oil feed in a couple of small containers. I would tension the crap out of the chain, lock it in place, bolt the housing cover on and give it a shot. If the problem goes away you know you are on the right track.
Or have I missed something? I am presuming you can run the engine with those tensioners.
Regards
Alan

Alan,

I did test the engine with the mechanical tensioners installed (left and right banks). With the ignition disabled, the engine turns very smoothly ang quiet. But once you connect the ignition (CDI), the knocking/rattling noise is quite scary.

I also performed disconnecting the spark for cylinder and run the engine. After doing cylinders 1-2-3, decided not to proceed to the other side. Too much noise and getting worse.

What I found out that you could run the engine without the chain covers but not too long because the oil is spilling out. If I have an extra chain housing covers, I would cut the upper section and the lower halves to run the engine (next project).

Tony

[Walt Fricke]

Unquestionably it is the best practice to replace the sprockets with the gears.

But I've skipped this several times with no obvious bad effects, at least in the short term.

Perhaps the simplest and most immediate thing to do is replacing the left side chain with the split link replacement to see if a) the tensioner piston and arm are more where they should be, and b) if the noise is gone. Could the noise be the piston hitting its stop repeatedly?

If this makes the noise go away, you can perhaps discuss with the owner - go with what you have got, since chain wear elongation is what caused the noise, or a complete teardown again to replace the IS sprockets? Or in between - replace the cam and idler sprockets. Hardly optimum, but I doubt anyone can quantify by how much this will shorten the reasonable street service life of this motor.

What if, even with a replacement chain, you still find the tensioner overextended and the idler arm too far up? First off, since it seems that only the left bank has this feature, that sort of rules out a narrowing of the case due to the mating surfaces having been shaved so that it could be line bored back to standard (plus that doesn't involve taking off enough to do this, does it?). If the case spigots were decked, or the heads decked, or both, that is going to increase the compression ratio. You could do a compression test to see of the left bank readings are higher than the right ones?

But bravo for being willing to take on this literal basket case. Lots of shops refuse to do this kind of thing because they don't have the knowledge gained by doing the tear down and the machine work etc.

My understanding of chain wear is that the pins wears a bit, as do the cylindrical pieces which pivot on the pins. Not much, but there are lots of them so it adds up. Of course, these chains lead a pampered life compared with motorcycle chains (and gears) out there exposed to dust and other abrasives. Or are MC chains nowadays encased and bathed continuously in oil?

And the wear I see on my sprockets is mostly on the sides and tips, and not down in the valley where the rollers go - although this is only from looking at them, not from careful measurement.

When my left side idler arm cracked, it was up even higher. But I found this when reassembling an engine which was apart for completely unrelated reasons. Lucky I caught it, but it hadn't been making the kind of racket you just can't ignore before I had the motor apart - a race motor, though, with a very noisy exhaust.

[Alan L]

So even with the chains fully tensioned, you till got knocking noise. I would suspect not the chains, altho they may have stretch. Hopefully some of the engine builders can confirm - but it sounds unlikely that chain slap would cause the noise with the mechanical tensioners tightened up. If it was chain slap you would expect to see some marks in the chain housing somewhere?
Regards
Alan

[Alan L]

FWIW, I replaced the chains on my SC when I split the case at around 220,000km. I am conscious of sprocket wear on motor cycles and usually replaced sprockets - but I did not replace the SC timing sprockets. I can only assume no discernable wear. Some 60,000km later I have no chain tension issues - I fitted the carrera tensioners at the time.
Alan

[boyt911sc]

I spent the day cleaning my work area and pushing the engine test stand aside in preparation for my travel to CA in a couple of days. But I kept thinking about the culprit all this time and getting back to this forum more often. My wife was getting annoyed why I am spending too much time in this forum. I still have a couple more days before my departure and will look closely look at the idler gear arm.

The best way to describe the abnormal noise is 'hammering'. I will remove the chain housing cover for the nth time and look for any sign of metal to metal contact or abrasion. Will keep you guys posted.

Tony

[Alan L]

If the chains are causing the hammering, there HAS to be a mark somewhere. Can you feel it - if you put your finger on the chain case? That is why I like the long screw driver over the stethescope, sometimes. While the stethescope is very sensitive to the noises, the screwdriver will transmit vibrations very well. The closer you get to the source, the more you feel it. And hear it. I would put the screwdriver on the chain cases and the cylinders - if that produces nothing, then the engine case.
Alan

[Sub8]

There is also potentially the issue with a worn woodruff key mentioned by another poster in this thread.

With engine firing you have a pulsed torque going into the system from the pistons. With a starter you have continual torque applied to flywheel. This is why you get different effects. I think it's probably time for a complete tear down! The only other thing I might do first is the cylinder by cylinder spark disconnect allready mentioned and maybe a complete bank disconnect and observe effects. Good luck!

[boyt911sc]

Originally Posted by Sub8

There is also potentially the issue with a worn woodruff key mentioned by another poster in this thread.

With engine firing you have a pulsed torque going into the system from the pistons. With a starter you have continual torque applied to flywheel. This is why you get different effects. I think it's probably time for a complete tear down! The only other thing I might do first is the cylinder by cylinder spark disconnect allready mentioned and maybe a complete bank disconnect and observe effects. Good luck!

James,

I did the splug plug wire disconnect test for cylinders 1-2-3 and decided not to continue for cylinders 4-5-6. The noise was getting noticeable and discouraging. It has been almost a month since I worked on this problematic rebuild and concluded to do another engine teardown after my return from vacation.

On the eve before I left (about 14 hours before my scheduled flight), I decided to do another quick test. With the chain housing cover removed and a known hydraulic tensioner installed, I ran the engine for a couple of seconds. The idler gear arm was not coming in contact at all with chain housing. I repeated the test several times with a wooden tongue depressor placed in between the chain idler gear arm and the housing during a brief run. No contact on the wooden tongue depressor but the loud noise still persisted.

Final verdict: Perform a complete engine disassembly and investigate the root cause of the problem. I am coming back home after 4 weeks being away and begin another adventure. Thanks to everyone.

Tony

[al lkosmal]

tony,
Greetings. I think you came to the right conclusion...it is tear down time.

regards,
al

[boyt911sc]

Al,

I was doing the engine teardown when I noticed something that caught my attention. The cam shafts nuts were not properly torqued and that could be the reason why the cam timing drastically changed (?). Re-did the cam timing @1.26 mm for both sides. Put everything back including the whole CIS unit. Removed the mechanical tensioners and installed the new hydraulic tensioners from Pelican parts.

To my surprise, the new tensioners were soft and spongy. I could compress the piston with my bare hands (?). These are the second set of hydraulic tensioners in three months span. Tests show that I have another set of defective tensioners that just out from th box.

The plan is to test run the engine after setting the cam timing for the 3rd. time and will be using a borrowed set tensioners from another engine sitting nearby. If the noise is still present during the next start up, complete teardown to follow right away. So I am keeping my fingers crossed and hope for a break. Will keep you guys posted.

Tony

[Mick_D]

I get the feeling I am going to need your patience when I go about building my motor. Tony. You're a saint.

[al lkosmal]

tony,
good to hear from you. I think that the camshaft nuts would have to be very loose for the timing to change. .....loose enough for the sprocket pin that locks the sprocket/timing in place to come loose.... but the looseness may have caused the noise.....it's worth a try. I'm not a fan of the Carrera, oil pressure fed tensioners. More stuff to fail in my opinion. If it is a rebuild and my customer already has them installed, I test them to verify they are good and leave them on....but I don't use them when I build an engine from scratch. My preference is to use 930 tensioners (old-school ) with hydro-stops to ensure that, if there is a collapse, they cannot cause the chain to jump. They are simple and straightforward and I've only seen one or two failed ones.............used ones, not new ones and the hydro-stops prevented total collapse. I noticed in a recent post by Henry Schmidt (Supertek), whose engine builds I admire, the he uses the same old-school tensioner setup...see link below.
68 soft window gets a new heart

regards,
al

[911pcars]

Originally Posted by boyt911sc

Al,

I was doing the engine teardown when I noticed something that caught my attention. The cam shafts nuts were not properly torqued and that could be the reason why the cam timing drastically changed (?). Re-did the cam timing @1.26 mm for both sides. Put everything back including the whole CIS unit. Removed the mechanical tensioners and installed the new hydraulic tensioners from Pelican parts.

To my surprise, the new tensioners were soft and spongy. I could compress the piston with my bare hands (?). These are the second set of hydraulic tensioners in three months span. Tests show that I have another set of defective tensioners that just out from th box.

The plan is to test run the engine after setting the cam timing for the 3rd. time and will be using a borrowed set tensioners from another engine sitting nearby. If the noise is still present during the next start up, complete teardown to follow right away. So I am keeping my fingers crossed and hope for a break. Will keep you guys posted.

Tony

Funny that both have failed to pressurize (both faulty out of the box?). Confirm they're both receiving engine oil by disconnecting an accessible feed line fitting, then crank the engine over until you see oil. If not, check for obstructions in the feed tube as well as at the banjo fitting outlet on the cam housings. In addition, inject a jolt of pressurized air into the tensioner oil inlet. This can sometimes dislodge a stubborn check ball to close as designed.

The archives contain more threads on pressurized chain tensioner issues.

Hope this helps,
Sherwood

[boyt911sc]

Originally Posted by 911pcars

Funny that both have failed to pressurize (both faulty out of the box?). Confirm they're both receiving engine oil by disconnecting an accessible feed line fitting, then crank the engine over until you see oil. If not, check for obstructions in the feed tube as well as at the banjo fitting outlet on the cam housings. In addition, inject a jolt of pressurized air into the tensioner oil inlet. This can sometimes dislodge a stubborn check ball to close as designed.

The archives contain more threads on pressurized chain tensioner issues.

Hope this helps,
Sherwood

Sherwood,

I had four (4) brand new hydraulic tensioners fresh from the box that were defective. See my other post in the Technical Forum. The batch of hydraulic tensioners Pelican Parts is selling has a very high percentage of failure in my experience. Four out of four were bad. I will try your suggestion to blast the inlet with pressurized air and retest. Stay tuned.

Tony

[boyt911sc]

After many months of ups and down, the engine is now running well without the annoying rattle and knocking noises that were observed earlier. I like to express my gratitude to the many people who assisted, directed, encouraged, etc. me to pursue and solve the problem/s.



The turning point started in the month of October 2016. After procrastinating and delaying corrective actions to solve the problem because of too many setbacks, I decided to go ahead and go for it. I started to do another engine teardown and investigate each part I removed. Half way through the teardown, something caught my attention and thought it could be the culprit(?). One way to find out was to re-assemble the engine again and do another start-up. Not worried or concerned about the result of another failed start-up, the result was what I have been waiting and expecting to see. To my surprise, it is running smoothly and no abnormal noises. Now, I could close this chapter and go on with my other rebuilds awaiting for their turn at engine test stand.

The moral of the story is to try your best and don't give up. Whether you succeed or not is measured by your 100% effort. End of story.

Tony

[Tippy]

So what was the problem?

[billybek]

Originally Posted by Tippy

So what was the problem?

It could have been this...

I was doing the engine teardown when I noticed something that caught my attention. The cam shafts nuts were not properly torqued and that could be the reason why the cam timing drastically changed (?). Re-did the cam timing @1.26 mm for both sides. Put everything back including the whole CIS unit. Removed the mechanical tensioners and installed the new hydraulic tensioners from Pelican parts.

[Tippy]

Originally Posted by billybek

It could have been this...

I was doing the engine teardown when I noticed something that caught my attention. The cam shafts nuts were not properly torqued and that could be the reason why the cam timing drastically changed (?). Re-did the cam timing @1.26 mm for both sides. Put everything back including the whole CIS unit. Removed the mechanical tensioners and installed the new hydraulic tensioners from Pelican parts.

That's not in the post above mine?

[Tippy]

Originally Posted by boyt911sc

The turning point started in the month of October 2016. After procrastinating and delaying corrective actions to solve the problem because of too many setbacks, I decided to go ahead and go for it. I started to do another engine teardown and investigate each part I removed. Half way through the teardown, something caught my attention and thought it could be the culprit(?). One way to find out was to re-assemble the engine again and do another start-up.

Tony

??