LS3 Timing Chain Failure :(
12-19-2008, 04:40 PM
#61
ATI is one of the best; used on C5R, C6R, and many other racing applications with the proper durometer elastomer tuned for their specific application. If you want an aftermarket balancer you can trust, ATI is it.
This is Kurt's comment from another post concerning a broken timing chain and dampers:
Check the links that are not broken for "tight" links. If you find tight links at the pivot point change the damper to the underdriven ATI with the low durometer rubber. This would happen in Motorola cup when the guys would drive to be "easy" on the engine. They would short shift and run the engine full throttle pulling up from lower rpm's and after about one hour doing this the timing chain would break for no reason. When I would inspect them, other links would be tightened up. ATI and GM worked with us on the repair, we added the timing chain damper and changed the ATI rubber to the low durometer and the problem went away.
Kurt
Kurt
Last edited by 405HP_Z06; 12-20-2008 at 12:14 PM.
12-19-2008, 08:21 PM
#62
I bought an ATI 10% under drive at Corvettes at Carlisle several years ago. One of their technicians was there and I spent some time talking with him. He told me they have not achieved the level of harmonic damping required with any under drive less than 10% and hence the reason they don't make it..….....
I was checking out the 2009 Fall/Winter ATI catalog and they now offer a 25% Accessory/10% A/C under drive balancer for the F and Y body. I guess they figured out how to make it work.
12-20-2008, 07:25 AM
#65
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Well, yesterday at the dragstrip my car had timing chain failure on the return road after making a pass. I put the car in second gear and pegged the throttle for a bit(this is a very long return road with nothing on either side but fields) and at ~3500rpm the timing chain broke.
Details on my setup. Vengeance Racing cam installed by them - 231/243 .617/.623 115 LSA, Comp 921 valvespring kit, hardened pushrods, ASP Underdrive Pulley, 160 t-stat, etc. Car made 483/435 to the wheels and my rev limiter is set to 6800rpm. My tune was dead on via my hardmounted wideband 02 sensor and my HP-Tuners logging software.
This setup has had exactly 8k miles on it with mostly highway miles and the car has never been road raced. Total miles on the vehicle is 15k miles. The rockers and valvesprings are in perfect order and show no failure. I will be having the valvesprings tested for pressure to determine if they were the culprit. I had plans to replace them once my combination hit 10k miles. My intake valves are not broken at the head, but merely bent.....which was surprising considering the nature of their design(2 piece welded hollow stems).
There was no indication prior to the break that anything was wrong. There was no sound preceding the break that indicated the valves made any contact at all with the pistons(I had the windows down). I think this is purely a timing chain failure and that being the case, I have absolutely 0 confidence in the car as of right now. How could I ever want to rebuild the car stronger or better when the only thing I can't make stronger is the damn timing chain. The Katech chain isn't stronger, but pre-stretched and heat treated I believe? Thats not enough to give me the confidence I am after and there is no double roller option available for this car(even though I am told people break those just the same)
Updates will follow as more details become available.
Pictures on Page 2.
Details on my setup. Vengeance Racing cam installed by them - 231/243 .617/.623 115 LSA, Comp 921 valvespring kit, hardened pushrods, ASP Underdrive Pulley, 160 t-stat, etc. Car made 483/435 to the wheels and my rev limiter is set to 6800rpm. My tune was dead on via my hardmounted wideband 02 sensor and my HP-Tuners logging software.
This setup has had exactly 8k miles on it with mostly highway miles and the car has never been road raced. Total miles on the vehicle is 15k miles. The rockers and valvesprings are in perfect order and show no failure. I will be having the valvesprings tested for pressure to determine if they were the culprit. I had plans to replace them once my combination hit 10k miles. My intake valves are not broken at the head, but merely bent.....which was surprising considering the nature of their design(2 piece welded hollow stems).
There was no indication prior to the break that anything was wrong. There was no sound preceding the break that indicated the valves made any contact at all with the pistons(I had the windows down). I think this is purely a timing chain failure and that being the case, I have absolutely 0 confidence in the car as of right now. How could I ever want to rebuild the car stronger or better when the only thing I can't make stronger is the damn timing chain. The Katech chain isn't stronger, but pre-stretched and heat treated I believe? Thats not enough to give me the confidence I am after and there is no double roller option available for this car(even though I am told people break those just the same)
Updates will follow as more details become available.
Pictures on Page 2.
Steve
12-20-2008, 09:14 AM
#67
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I'm guessing this is the root cause of the problem. It would be nice if the OP posted pics of the chain and damper. I've been running an ASP pulley with the LS2 chain and damper with zero problems for 3 years on this setup. It shifts at 7200 rpms and goes through the traps at 6400-6500 rpms.
12-20-2008, 09:41 AM
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12-20-2008, 09:42 AM
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I'm guessing this is the root cause of the problem. It would be nice if the OP posted pics of the chain and damper. I've been running an ASP pulley with the LS2 chain and damper with zero problems for 3 years on this setup. It shifts at 7200 rpms and goes through the traps at 6400-6500 rpms.
12-20-2008, 02:05 PM
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I am looking for comments on what people think of the chain failure and how my pistons look. The piston pictures are in order from 1 through 8.
I think my chain may have been defective. It failed at the master link and the pin was still intact. The link is what failed, which from what I have read, is rare in the fact that most of the time, the pin is what fails. Anyways, here they are:
I think my chain may have been defective. It failed at the master link and the pin was still intact. The link is what failed, which from what I have read, is rare in the fact that most of the time, the pin is what fails. Anyways, here they are:
Last edited by 1.8t; 12-20-2008 at 02:40 PM.
12-20-2008, 03:32 PM
#74
After several hours trying to research this at PRI last week, it seems that it is a harmonics issue and each step further from the stock Gen lV (late LS2) as supplied by Cloyes with a stock set, tensioner and stock damper is a move closer to potential failure.
Perhaps some single IWIS or JWIS chains are stronger but they still vibrate as a result of the specific LS induced harmonics. Maybe some chains such as doubles are stronger and heavier, but due to the harmonics seem to stretch more which is also potentially fatal. The stock GM damps are heavy and clunky (power robbing) but are optimally designed to work with the specific vibrations set up in LSs. It is acknowledged that the most stressful time for a chain is on throttle lift around torque peak ~5200rpm. Some aftermarket damp manufactures such as ATI have done more research into the issue but it is not prudent for them to produce a damp which has no power advantage over a stock damp. The softer rubber seems to improve the vibration characteristics but does not last as long and only approaches the total dampening of the stock setup.
The C5r,C6r and other race applications may use "proprietary singles" but they also use damps unlike those cited above due to the front dress incorporating an aftermarket dry sump and multiple single drive belts.
In the end opinions may vary, but I came away thinking anything other than a fresh, tight OEM spec single chain with stock damper is a compromise. The stock setup is not realistic where every hp counts but---
Perhaps some single IWIS or JWIS chains are stronger but they still vibrate as a result of the specific LS induced harmonics. Maybe some chains such as doubles are stronger and heavier, but due to the harmonics seem to stretch more which is also potentially fatal. The stock GM damps are heavy and clunky (power robbing) but are optimally designed to work with the specific vibrations set up in LSs. It is acknowledged that the most stressful time for a chain is on throttle lift around torque peak ~5200rpm. Some aftermarket damp manufactures such as ATI have done more research into the issue but it is not prudent for them to produce a damp which has no power advantage over a stock damp. The softer rubber seems to improve the vibration characteristics but does not last as long and only approaches the total dampening of the stock setup.
The C5r,C6r and other race applications may use "proprietary singles" but they also use damps unlike those cited above due to the front dress incorporating an aftermarket dry sump and multiple single drive belts.
In the end opinions may vary, but I came away thinking anything other than a fresh, tight OEM spec single chain with stock damper is a compromise. The stock setup is not realistic where every hp counts but---
12-20-2008, 03:50 PM
#75
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I fail to see how an aftermarket chain can induce crank harmonics into the equation. Afterall, if crank harmonics is what were are saying caused this failure(note, no other links were "tight" at all, it just looked like a fatigue failure), how is an aftermarket chain going to do anything but increase my odds against another failure. I am going to be keeping the stock damper, but I feel a stronger chain on the stock gears and the stock harmonic balancer will be my best defense against this kind of failure in the future.
12-20-2008, 04:02 PM
#76
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Actually, its the other edge that "looks' different. I will try to get some pictures.
12-20-2008, 04:05 PM
#77
I fail to see how an aftermarket chain can induce crank harmonics into the equation. Afterall, if crank harmonics is what were are saying caused this failure(note, no other links were "tight" at all, it just looked like a fatigue failure), how is an aftermarket chain going to do anything but increase my odds against another failure. I am going to be keeping the stock damper, but I feel a stronger chain on the stock gears and the stock harmonic balancer will be my best defense against this kind of failure in the future.
A OEM spec with stronger materials can't hurt. I understand the EWIS uses a stronger polished alloy for the side plates.
12-20-2008, 04:13 PM
#78
Some aftermarket damp manufactures such as ATI have done more research into the issue but it is not prudent for them to produce a damp which has no power advantage over a stock damp. The softer rubber seems to improve the vibration characteristics but does not last as long and only approaches the total dampening of the stock setup.
Here's a picture of a few of the race hubs offered by ATI for LS engines. Talk about serious underdrive!
Agree and disagree. I'm still convinced the ATI damper offers better harmonic dampening than the stock damper.
12-20-2008, 04:22 PM
#79
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Both my chains broke at the links and not the pins.
Now I'm confused on which TC dampner to use with the IRL chain.
I believe the Harmonic Balancer is the culprit in my situation. I ran the car hard at the track stock and with a Maggie sitting on top. Then I did the H/C swap and ASP underdrive (minus the maggie). Two days at the track and 2 months of street driving and the LS2 chain went. The stronger double just stood up the harmonic longer. I am hoping the ATI and the IRL chain will prevent this from happening again.
We need a camera inside there to watch what is going on. Maybe someone can make a clear cover.
Now I'm confused on which TC dampner to use with the IRL chain.
I believe the Harmonic Balancer is the culprit in my situation. I ran the car hard at the track stock and with a Maggie sitting on top. Then I did the H/C swap and ASP underdrive (minus the maggie). Two days at the track and 2 months of street driving and the LS2 chain went. The stronger double just stood up the harmonic longer. I am hoping the ATI and the IRL chain will prevent this from happening again.
We need a camera inside there to watch what is going on. Maybe someone can make a clear cover.
