I've stated it before and I'll state it again. It's not the imbalance of the balancer that is the issue. It's the total spring-mass system. I'm obviously doing a completely terrible job of trying to explain torsional vibration. Think of it this way. If I have a rope with a weight on the end of it and let it swing, it will swing at it's natural frequency. Now if I put a lighter weight on the end of the rope, it will swing faster (this is how grandfather clocks are adjusted for fast or slow time). That's all I am saying. You would have to check with the GM Engineers that designed the LS3. They sized the front balancer to keep the torsional natural frequency out of the operating range of the engine. A lighter front balancer will change the torsional resonance. Maybe not enough to be a problem, but it's a possibility.

 

Here is the same discussion on LS1tech for those that want to see some other opinions being offered. http://www.ls1tech.com/forums/genera...n-failure.html

 

My opinion: The OEM chain is marginal. Chevy timing chains in both the small block and the big block have been marginal since the first Chevy V8 in 1955.
When we install aftermarket cams we also install higher rate valve springs. These new springs apply far greater force to the cam (this is multiplied by 16 valves) and this greatly increases the demands on the chain. We should expect failures in these applications.

Another enemy of timing chains is down shifting as it snaps the chain from loading in one direction to the opposite direction.

A Jesel belt drive with the new white Rino belt would be the ultimate setup as it isolates crank harmonics from the camshaft.
A great alternative would be a good quality double roller like the Cloyes. They use a Reynolds chain that is virtually unbreakable. We should all call Cloyes and express our needs. If they perceive a market, they will make a product.

 

Some excellent points! I have been trying to explain the problems with aftermarket dampeners and even though there are differences, I agree with Spin that they are most likely not the cause. However, there is a difference which will keep me from ever using one. I also agree that the stiffer springs is the main reason for higher chain loading. A higher power engine only loads the chain more from the standpoint that it can accelerate more quickly (and thus the T=I*alpha is higher, where T is torque, I is the rotating inertia of the camshaft/valvetrain, and alpha is the acceleration rate). But the accel loads are most likely much lower than the spring loading.

I have the stock valvetrain on my 06 C6 and will most likely keep it this way for several reasons. But I (yes, I did my own install) did install a 224R cam in my 01 Z28 and I used the Rollmaster double chain set-up on that LS1. I've since sold the car to a very good friend and I'm sure glad I didn't leave the stock chain. The funny thing is that a few years ago the LS1 guys were raving about the LS2 chain saying it was much better than the LS1 chain. I guess they were wrong.

Thanks,
Glenn

 

Interesting. So you're saying it's not necessarily a HP to strength condition but rather the load pressure from the upgraded valvetrain. Something that almost always accompanies a cam swap. Do cam specs have anything to do with it or do you feel it based more on spring pressure?

 

I think its me that is having the trouble with the message: The LS1 and LS6 have the exact same crank and UD pulley and they didnt have this chain breaking problem.

Since its the same UD pulley and crank, it isnt the issue since it wasnt until the chain/timing sensor relocation came into effect.

 

All springs have 100% countered spring pressures from the opposing cylinders. The sum net force is zero unless you have a weak out of spec spring. Opening ramps on a cam have the closing ramps of the opposing cylinders to counter the force. The sum net is the same for any strength spring pressure.

 

And they are running the exact same UD pullies with no failures.

 

LS1/6's rarely make north of 450rwhp.

 

Spin, just a couple of points. First off the rotating group includes the rods and pistons and the LS3 is different than the LS1, LS2, and LS6. Plus, I'm not sure of your statement that LS1's do not break chains, because they do. They've been known to snap stock chains, LS2 chains, and dual row chains (according to postings over on LS1Tech.com). I'm not sure if all of these failures included an UD pulley.

Spin, this is a complicated problem and I'm not saying you are not correct. But to make the statement that the LS1, LS6, and LS3 have the same crank may be correct, but they do not have the same rotating group. Even though the rods and pistons do not contribute to the torsional spring rate, it does affect both the mass and the dampening. Also to make the blanket statement that the LS1 and LS6 do not break chains is not correct.

 

100% CORRECT! Absolutely correct....However, I would add if not stated before, The more power you make and the higher you rev it (Cameron, Are you listening???) the stronger these harmonics can get and eventually lead to a failure such as this.

I believe that a "harmonic" balancer can have a positive or negative effect on the valvetrain depending on the application. Realize that the underdrive pulleys we use MIGHT NOT be "HARMONIC" ballancers engineered for the HP/CAM/RPM's/etc. the way we are using them and that HARMONIC BALLANCERS or pulleys should be engineered or calibrated for the intended application.

The ones we are all using have been designed for the AVERAGE application.....but, after you mess with *EVERYTHYING* in a motor and REV IT UP a few times....you're likely not using a balancer that was designed for the way you're using it.

Purchasing an application specific balancer is likely extremely expensive and more likely not available for our purposes....Face it...We've all used MANY different cams, springs, lifters, and combinations and it's not likely that the available BALLANCERS/UD PULLEYS are appropriate for all applications.

ALSO, Keep in mind...There are "HARMONIC BALLANCERS" and there are just simply "underdrive pulleys". Sure they can be the same thing....but likely, they are not.

The engineering that goes into a "HARMONIC BALLANCER" is much more complicated than just simply machining a smaller diameter pulley with smaller groves.

Also, I believe that because an underdrive pulley is SMALLER than a full size ballancer there is likely LESS HARMONIC damping.

A BALLANCER is designed to absorb or cancel harmonics from primarily 2 events.

1) firing events of cylinders

2) flexing or twisting (and obviously UN-TWISTING) harmonics of the crank...Forget that the crank is steel....Think of it as being made of rubber twisting back and forth.

I believe that VALVETRAIN harmonics effect (or are effected by) the HARMONIC BALLANCER, but there is more to consider.

While some of you have mentioned this only happening to STICKS...You're onto something.

Most of you that have ventured to monster cams, have likely went the clutch replacement route.

While these crank pulleys and flywheel/clutch assemblies are considered "ZERO BALLANCED" on these motors, adding and subtracting weight front and rear most absolutely changes the mass of the rotating assembly and thus effects the engines overall harmonics.

I saw someone mention abrupt RPM changes. Yes, most likely with a stick....and Hmmmmmm... Maybe more likely with a BRONZE or PUCK type clutch where engagement is a bit too harsh....

Don't think that your amazingly quick (insert Cameron's name here) "Look what a QUICK shifter I am..." speed shifting without the clutch manuver dosen't have an effect here...

There's more than one thing happening here.....Look at the big picture.

I tell all of my customers...If you drive AGGRESSIVELY, just do this one thing for me.

Put a big jar of M&M's or (Reice's Pieces if you prefer...) on the dashboard.

Make it a rule that EVERY TIME you stab the throttle...You take and eat 1 M&M.

Depending on how often and how hard you beat your car....EVENTUALLY, YOU WILL HAVE NO M&Ms LEFT.

And that's a fact.
Chuck CoW

 

OK, so with differing cranks on stock motors vs strokers, and varying piston weights for different bores and subsequent varying harmonics on rotating assemblies, we have come to the conclusion that the epidemic of chains breaking is on all LS engines including the LS1,2,3,6 and all stroker sizes (with and without UD pullies) so we can now conclude.....? Nothing.

I'm not sure what the statements were meant to prove or disprove other than there is a possibility that any part including the stock pulley can contribute to chain failure. My only contribution to this thread was to point out that the UD pulley can and has been at home on many motors with high HP and havent killed the chain. This thread most certainly started out trying to show the UD pulley contributed to the chain failure then at the end it is simply reduced to a statemtn that it can contribute to chain failure. Since the stock pulley has been on FI motors with a failed chain and the stock motor has also had failures with the LS2 motor with all stock parts so nothing has been proven here.

Use the stongest chain you can get and dont cry if it gives out since the formula for what is better isnt here in this thread.

I would like to point out one thing we can all agree on. People such as my opinionated self can hop in a thread and be forcefully debated by others without people getting personal or rude. I was actually trying at one point to 'push it' as a test to myself and still none of you went there. This is the best forum of its type and I'm really happy we get along enough without mud slinging and name calling when we dont get the other guy to agree. It says something about vette owners here and I'm proud to be part of it. This is how all the opinions get out and we all learn.

 

Like I said in a previous post, you were most likely correct. Thanks for all your knowledge and input and I totally agree with you that you should use the strongest chain that you can! I also appreciated your comments on the springs canceling each other out, I ALWAYS forget that. That's why my forehead is flat, I'm always slapping it when I read things like that.

Thanks,
Glenn

 

So can we compile a list of the best possible route to prevent timing chain breaks? Stronger chain, new timing set, an appropriate chain damper, etc...

 

This is true, if you sum the forces from a full two revolutions (720 degrees) turning of the crank. I have turned over enough LS engines with breaker bars on engine stands with the spark plugs removed to feel the uneven torsional resistance due the the valve springs loading and unloading. The forces aren't simultaneously balancing themselves out. The vibrational dynamics of crank engines is a very complex subject, LS1/LS6 engines can have a markedly different vibration signature from the larger bore LS3. My choice for a stressed engine build would be an ATI damper, JWIS chain and a rebalanced rotating assembly.

 

I'm not in the camp that is blaming it on the UD pulley. I was just noting that it was and still is considered an "upgrade' for the LS1/6 guys. I realize H/C LS1/6s aren't averaging much over 450rwhp but when going FI/N02 they are. So my question is, is it strictly power related or is it power from a bigger cam that is causing the issue? Since a cam inherently changes the operating manners of the entire engine is this what is effecting the chains integrity? Just trying to learn.




If people didn't have differing opinions no one would ever learn anything new. There's a lot of information out there and I know it gets frustrating when it's so clear to you (you meaning in general) but someone else doesn't grasp it. Insults and personal attacks doesn't help anyone. I'm always open to learning things but I wont always just take someone's word for it. I like to see evidence backing up the info. I don't mean any disrespect by not immediately believeing it, it's just how I am.



you stubborn sob

 

Yes, I did. I would say it was pretty bad at times, but everytime the car would hop, I would get out of it and get back in it. It was bad enough that if the car had kept hopping, something probably would have broken.

Does this have a role in the break?

 

Katech lists their C5-R chain for $139.94 at http://www.katechengines.com/street_...tail.php?id=24

Lingenfelter used to show an IWIS chain as part no. KAT-G68V-2 for $168.95 at http://www.lingenfelter.com/store/kat-g68v-2.html

but now LPE shows a chain from IWIS at a NEW LOWER PRICE of $49.95 at http://www.lingenfelter.com/store/hme-g68v-2.html

SO . . . . . is the $49.95 LPE version what we need ? ? ?

 

I think the reason is the underpants you are wearing. Breaks occur when wearing anything other than a boxer-brief. That's what I wear and have not had a failure yet.

Having said that, in my crap opinion I think its due to slop and hard forces. The chains have lots of play or slop in them, both factory and even some aftermarket. The harder forces can be any force you put on the motor that might be outside factory intentions. So, no mods and drag or track use, heavier springs, different cams, harmonics in a new balancer. It all adds up. My point is that we've proved that outside factory intentions the chains fail. I know they flog them at GM, but they don't flog every motor and it seems its a crap shoot as to what you get. So, what can you do?

Really all we can do right now is to try and mitigate the slop and hard forces on the motor. I'm not going to change my driving so that's out.

What I did, and I have no failure... yet, is

I installed the tightest chain I could find. Which happens to be a Katech on JP gears. The JP gears come in whatever timing set Texas Speed sells. Its marketed as many different names.

I actually used a feeler gauge and pushrod checkers to determine the right length for my set up. It was hard to find rods, but I got real close. Hyd lifter or not, I wanted to reduce any forces on the cam and chain.

Checked, double checked my installs.

I compression brake my car all the time. That probably equates to some squirrly track driving. No failures yet. Maybe I got a good motor, maybe its going to break tomorrow. But, I have done what I can think of to reduce my chances of failure. What else can we do? The double roller install is more than I want to do.

As another data point, I had a lifter break adn jam up the cam. Completely stopped it. Stock chain did not break, it actually tore off the timing gear. Chain still intact. So, I guess some of the stock chains can take some intense force.

In the end I agree there is something wrong in the design somewhere. I don't know if we'll ever figure it out. It would take collecting all the broken motors and looking for a common thread. I'll do it if you ship me all your broke engines

As for the discussion about zero net gain and harmonics and all that stuff, I get it enough to get it. I can't however go on to say one of these things are causing the failures. Again, I just try to mitigate outside forces on the motors with proper parts and set ups. We might do everything in our power and still experience a break.

 

I just got off the phone with some of the boys over at Cloyes. He said they had tested the Katech chain and it offered little more snap strength than the stocker. He gave me a part number for their strongest chain, which is now listed as obsolete due to almost 0 demand because of expense and the advent of double rollers. The timing chain part number is 9-194 and the cheapest price I have found is $360 just for the chain. According to Mike Sinnea @ Cloyes, it is prestretched, media blasted, hand selected pins and links to ensure proper gaps, the alloy of the steels used are better, the pins are a chrome style alloy, and it has been heat treated.

They have made this chain for a while and it will work with stock gears according to him, but the double rollers and the LS2 chain have pretty much taken over this chains place in the market. You should still be able to get it through Summit Racing though.