Seems it has come down to the higher stress to the chain comes when coming OFF throttle in the mid range (higher torque). It is at this time that load on the chain is reversed abruptly.

 

Okay, Please forgive me as i did not read the entire thread, but from what i have read is that the ASP is possibly the culprit to these broken timing chains? Ive got quite a bit of vibration coming from either the (Stock) harmonic balancer, something internal, or the flexplate, as i have already ruled out everything from the converter back. I was actually considering getting a ASP until i came across this thread..... What's one of the best Harmonic Balancers? ATI, powerbond, or how about the fluiddampnr?? I just need something that will soak up as much vibration as possible.

(Sorry for the thread Hijack....)

 

In my opinion, ATI and no more under drive than 10%.

 

^^^

 

This is just an anecdote on its own... But this thread seems to be compiling some results sooo....

I road race my 99 TA... It has seen three track events (1 MAM, 2 BIR) events and about 10k of street miles over the last two years. I have the March damper/pulley on mine and the TC was stock up until late last year. When I did the heads/cam upgrade, I put an LS2 chain on it but the stock chain looked fine. The engine did have to come out again after the heads/cam upgrade as I had an oil starvation issue, but the TC was reused and looked fine. I tend to take it a little bit easy on upshifts to save on the trans/clutch, and I also match RPMs as well as I can on decel - on the street too... I suppose I will cross my fingers from now on then ...

 

Ya know the more I think about this the more I wonder on application. I kicked the living **** out of my LS1 with the wimpy stock LS1 chain on there for 20K miles and hundreds of track passes. God knows how many times that motor saw 6500+ it Has had an ASP pulley on it for 16 of those 20K miles. I could see a road race application really being rough on a TC. Drag racing dont see nearly the amount of rpm transitions. I'm set on using a C5R chain from Katech and an LS3 tensioner but i'll be damned on this ASP balancer. It's never easy is it? LOL

 

I finally had the last piece of the puzzle tested. All of my valvesprings measured at 140lbs on the seat and 360lbs @ 1.220". Comp's specs for these valvesprings is 135lbs at the seat and 400lbs at 1.220" with a spring rate of 408lbs/in. What I don't understand is, if you take the difference between the installed height of 1.770" and Comp's open load height of 1.220", you get a difference of .55". Using the spring rate of 408lbs/in multiplied by the height difference of .55", you get 224.4lbs. Add this to your seat load and your right at 360lbs @ 1.220". Why does this method not sync up with what Comp has listed?

Aside from that, all of my valvesprings were fine. That is more than enough pressure to keep things in check with my cam reving to ~6700rpm.

 

With great respect to all whom posted (and there are some notable, knowledgeable posters in this thread), and no, I have ZERO affiliation with ASP (would be good to have them chime in actually), I think it may be "fuzzy logic" to suddenly condemn ASP pulleys, claiming they are the "smoking gun" to cam chain failures..

Point #1 - I would put money on this - for every 100 ASP pulley sold, 3 Powerbond's and 2 ATI's are sold. Just on sheer volume, and considering ASP is by far the most popular aftermarket pulley (or was until very recently), it makes sense that *most* motors suffering cam chain failures will occur with an ASP pulley installed because *most* cars running aftermarket cams used in a performance situation have an ASP pulley installed.

Point #2 - I am not discounting the importance of a properly designed dampener, however.. The stock dampener has an aluminum hub / center, and is around as light as one of the lightest aftermarket pullies (ASP). Yes, I understand there is much more to this than shear weight, I am sure ATI can explain the complexities in great detail, and I know they are vast. Still, just look at racing motors that basically eliminate any sort of crank-mounted dampener. Yes, race motors have parts swapped all the time, and that brings me to the next point.

Point #3 - Making the logic jump that employing race-bred parts (whether it be a timing chain, dampener, valve springs or anything else for that matter) results in a "bullet-proof" build when subjecting said parts to the same conditions experienced by a racing team (say, road race track car (like the 04 Z06 mentioned in this thread) but without the aggressive (impractical for most of us) component replacement schedule.. Think about it - I have no proof (Jason does), but do you really think the GM team manager saves a few bucks by leaving in that super expensive - heavy duty "bullet proof" TC between rebuilds (which happen in hundreds of miles, not tens of thousands)? Its apples to oranges folks.. Saying "GM racing has never had a failure with XYZ TC" is like saying "my African Elephant repellant works great; haven't seen one in my back yard yet"..

Bottom line IMHO..

When it comes to timing chain reliability / survivability, I would think the order of importance is as follows;

1. Use - driving style and type - road racing / constant wrapping up to redline / downshifting for hours at a time is certainly harder on components than 1/4 mile runs and street driving.

2. Valve springs - if they float and valve meets piston, that creates way more load than a timing chain was designed to handle.

3. TC quality - obviously of major importance.

4. TC dampener - I am kicking myself for not installing one when I did my cam swap, but to be fair I would have had to tap the block.. And now it appears GM stopped making them, so 2 strikes for me. I have a background / understanding of chain harmonics / dynamics, and I can say with some confidence that a TC dampener is a GREAT idea, hence they are on newer GM designs from the factory, and we all know they do only what is absolutely necessary ($$).

5. Crank dampener - I am sure the size, type and design does play a factor in ALL aspects of bottom end reliability, but it is my understanding an improperly designed dampener has greater impact on crank / bearing longevity than being the likely cause of TC failures.

 

I would agree the lower priced units do sell more than the higher priced units, but not at the ratios you state above. I can only assume your using the numbers to illustrate the point that lower priced dampers sell x:1 units as compared to higher priced dampers. This is a common phenomenon seen across any market, any product. It does beg the question, Why so many timing chain failures with ASP damper with no reported failures with the ATI damper? Going by some assumed market penetration ratio, if it wasn't the damper I would expect to see reports of timing chain failures with the ATI damper, albeit with a much lower occurrence.

The stock C5 damper has an iron center and steel outer ring isolated by rubber. It is not the lightest damper on the market and neither is the ASP. The ATI is the lightest damper that I know of for the LSx engine. See weight chart below. As you state, weight is not a single determining factor for damper effectiveness.



Good feedback!

 

Aaron - to clarify.. My handy super-strong magnet indicates the inner hub of a stock GM Y-body dampener is not steel - but the outer ring / drive hub is.. So either the inner hub is aluminum or something different from common steel.

On the weights - Maybe I should have stated "the ASP is lighter than the stock dampener".. You've educated me on the ATI - I had no idea the ATI was lighter (and by a significant margin) than the ASP.. I guess you can't tell a book by its cover (the ATI certainly looks like it would be heavier!).

 

The inner hub is cast iron.

 

I am the guy that broke two chains while running an ASP. It may not be the ASP pulley's fault alone. My stock balancer had weights added to it. I know many say the LS1/6/3/7 are internally balanced but the service manual says otherwise. I cut and pasted below. I assume the ASP is zero balanced and my factory pulley was not.


The 1997-2004 5.7L LS1/LS6 engine with crankshaft balancer is a balanced assembly. On manual transmission applications, the flywheel, clutch, and pressure plate is also a balanced assembly. During the powertrain build process, balance weights may be added to the crankshaft balancer and/or flywheel as required.

In order to maintain engine/clutch assembly balance, it may be necessary to install or remove balance weights as detailed below:

Crankshaft Balancer
Existing balancer onto existing engine: The balancer position must be marked prior to removal and installed to the original position. Refer to Crankshaft Balancer Removal .
New balancer onto an existing engine: Install the same size balance weights into the new balancer in the same location as the old component. Refer to Crankshaft Balancer Cleaning and Inspection .

 

Are most of these failures on Corvette balancers?

 

That's not how you calculate spring force...

F = -k*x where x is the displacement from the springs unloaded free length, not the difference in installed seated length minus loaded length...

So you first have to find your spring's unloaded free length z...

You said you measured:
(a) 140 lb at 1.770" (seated height): x = z - 1.770
(b) 360 lb at 1.220" (loaded height): x = z - 1.220

So now you have to solve (a) and (b) for z (unloaded free length):

(z - 1.770)/140 = (z - 1.220)/360
(z - 1.770)*360 = (z - 1.220)*140
(360 -140)*z = 1.770*360 - 1.220*140
220*z = 637.2 - 170.8
220*z = 466.4
z = 466.4/220
z = 2.120"

so now, calculating x (the displacement from unloaded free length) and multiplying by spring rate:
(a) x = z - 1.770 = 2.120 - 1.770 = 0.35" --> 0.35" * 408 lb/" = 142.8 lb
(b) x = z - 1.220 = 2.120 - 1.220 = 0.90" --> 0.90" * 408 lb/" = 367.2 lb

This agrees with what you measured.

Edit: I didn't see this part, so please ignore my post.

 

Thanks Joecar! We can always count on the engineers!

 

I reread your post and I now see this part...

I am sorry I didn't see it before, please ignore my post.