i used to some years ago for a lil street action.
i may come to mobile dragway couple times a year.

 

I would have to agree with the crank endplay advice as well. That seems to be a VERY logical answer.

Also this is a little off subject, but a buddy of mine had a problem similar to endplay issues in his T-Type Buick.... and turns out his vigilante stall (when installed) was pushing his crank too far forward and causing it to chew up the bearings. He said he noticed it mainly at wot... He heard a ticking noise, and discovered it was coming from the trans/engine area. He pulled the stall and went with another 1 he had laying around and the noise went away. Unfortionentely he had to build another engine!!!
I'm not saying that this is even remotely close to your issue, But who knows. This is the first time I have EVER heard of a situation like his, but he said that after researching it more, there were many other people who said this was a common problem as well. At least on the GN's and T-Type Buicks!

GL with finding out this problem man! Thats pretty shitty to spend all that money and then have to deal with the SAME issue twice! I feel sorry for you having to deal with this! Hope you solve it soon!

James

 

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

 

^ I thought all corvettes had a TC damper from the factory? Would going back to the stock balancer be a good move?

 

I broke my second chain as well. It's a H/C 03 Z06 without the TC damper. I was running an ASP underdrive pulley. I use the car for HPDEs and the two breaks were on different Cams. I planned on using an ATI balancer/pulley on the next engine. Both beaks were while in the 5K rpm range. The redline on the motor is 6500 rpm. I took a look at the stock balancer and it does have two pins tapped into holes and marked with blue paint. I now assume the my factory balancer is not zero balanced. Maybe I caused a new vibration on the front of the crank by changing to a zero balance underdrive pulley.


When I get the motor out I will check for tight links and crank endlplay.

 

The TC damper was on the LS in development although it was a stamped steel part with small plastic inserts that clipped on at the chain contact point. By the time the engine was released in the 97 Vette it was not installed although the early engines still had the tapped holes in the block. I don't remember what year the factory started using them in production, but it was when the black dampers came out, the original service part was tan and used a different (narrower) bolt pattern.


Kurt

 

The ASP pulley is about the cheapest crank damper you can buy - certainly not up to track-day duty at sustained mid/upper rpms. We have an ASP at the shop now off of a customers engine and the rubber has completely hardened through and cracking, probably very near separating from the shells entirely - a real piece of junk I wouldn't even put on my street car.

The crank damper does just what it's name says, it dampens crankshaft torsional harmonics. Without a good damper on the crank nose, those harmonics WILL be hitting the chain like a hammer in the mid-rpms like Kurt said, and chain failure is only a matter of time. If you're having timing chain problems, the crank damper is the second place you should look after verifying chain alignment.

 

I ordered the ATI damper for my new build. The ASP will be a paper weight. This last time when the chain (double) broke it busted the oil pump right at the pick up. I'm sure it sent metal through the engine. I was on the track at the time and had to use the motor to help slow the car down (I exhausted the brake boost). I was able to get the car stopped from over 100 mph right before turn one at Summit Point. Never the less, I am sure I kept pumping metal fragments.

I got the chain out of the engine today and there are many links that don't pivot as freely as others. On the link that broke the pin is bent. The pins didn't break. The links did.

I am going to use the JWIS single chain (supposed to be the same as the C5R chain) the latest chain damper.

Reading posts about lifter failures, I upgraded the lifters to Morels as well.

 

get a double roller

 

Mad props to you road race guys. The stress you put on these motors is simply nuts. Best of luck on getting this problem taken care of.

 

ya its strange but i would just not over think it and replace the chain with a gm chain. as long as your sure there is enough spring to valve hight clearance during valve open.

 

Interesting side bar. Someone on CF has an early 97 and when they opened it up to replace the cam there was a metal bracket with a nylon coating used for a TC damper. Not sure if he kept the original parts but I told him to hold on to them as I think this was likely a very early motor with some rare parts.

 

Anybody have a part # for the low durometer ati balancer? thanks in advance!

 

I saved one for a novelty, but I can't remember what I did with it! Its not suprising that a few might have hit production as they did say they worked, but that it was not needed for normal driving. Wonder how many dollars they spent on warranty versus not installing them?

Kurt

 

I have a freind with a ls2 vette with 22,000 miles stock with a 76 @6lbs, his bolts sheared right off the crank. It happened just cruising around. Has anyone heard of this?

 

DING DING DING- +WINNER+ Stroked motor, aftermarket balancer, I bet my left nut and lock washer u got a balance problem. U don't by any chance have a dyno sheet showing the power dropping a couple hundred rpms b4 it should, do u?

 

What is the connection between the power dropping early and having a harmonics issue. My timing chain recently broke and I was running a ASP underdrive pulley. The cam is a comp grind, 236/240 610/605 lift on 112+2 LSA and was making peak power between 5950 and 6000 rpms and then dropping off. With the LS6 shortblock, TFS heads, ported 92mm fast, ported 90mm throttlebody and Kooks longtubes and offroad xpipe, I thought my power was dropping off too early also. I would have thought with my parts it should have easily pulled to 6200 to 6400 range, but dropped pretty quick after 6000 rpm. Let me know what you are talking about? My case looks textbook to what you are describing

 

I have a n00bish question...

has anyone invented a security device for breaking timing chains...

Like suppose lets say...

..Isnt there a safety cable or something that can be used on or attached to a timing chain, that IF the chain were to break, that cable or whatever will still keep it in place and at least there wont be severe PTV contact?? (the chain will break and you will definitely know, but the cable or whatever has a larger clearance area and it will prevent engine damage, if the chain breaks)..

 

how the hell are you going to get a "safety cable" in front cover? how would you attach it if you could? would it be a chain/belt drive system? is that what your talking about?

 

hi guys i think that i is the front pulley, i cant remember what make it was but at the back it is going metal to metal as there is not enough clearence for the rubber to work, you can see the metal has burred out at the back where it has been touching,i have replaced it with a new different type so time will tell.!!!!!!