I would bet money on the reason you keep breaking timing chains is that you do not have the correct balancer on your engine. Are you running some kind of "underdrive" crankshaft pulley that is not a harmonic balancer? Some of the aftermarkey pulleys REQUIRE you to use them WITH the stock balancer. I have heard of at least 3 people breaking timing chains because they just took the stock balancer off and installed an aftermarket pulley. In fact, I have never heard of anyone breaking a chain when this wasn't the reason. Check it out.

 

so you bought a cloyes chain, it broke, and theyreplaced it with a STOCK chain/gears? why didnt they put on another set of cloyes? I think thre's enough people out there using the cloyes to prove there worth. you might have just gotten a bad piece. then the stock ones could have broken for the exact reason you repl. them with an aftermarket chain to begin with. cause they are too weak to handle the load of all that power/rpms. what cam are you running? springs? pistons? valve to piston contactmight cause that I guess. def. check cam endplay too. does the cam spin freely? very odd. gotta be something goin on there. as someone mentioned, eng. vibration can cause this sort of thing too. good luck finding it.
chris

 

Wow, you broke 2 timing chains within 2k miles total, thats got ot be some kind of record.

Any wierd noises or anything out of hte motor? How free does it rev? did the power drop off b4 it broke the chain? maybe it floated the valves and banged them on teh pistons or something? I am at a loss.

I would look for stuff like, too much lift for the valve springs, too much lift for the pistion/valve clearence, wierd harmonics going on, lifter sticking in the bore, messed up valve geometry, and so on.

since aren't LT1 timing sets endless? they don't have a master link as a weekpoint right?

you have something making the cam drag and or stop that is making it break chains.

also might want to check the cam bearings, maybe one of them spun and is making the cam seize to the cam bearing?? But that would show up as an oil pressure problem.

could be hte oilpump drive has something making it work harder, but usually it just breaks the pump shaft or the teeth on the drive.

I would have hte machine shop take it ALL back apart, then put the cam in by itself and spin it ans see if it spins freely, then go from there.

 

I'm running the stock pulleys still. I'm thinking that valve/piston contact might be the problem. I'll know more soon though, motor should be out on Monday or Tuesday.

 

you might be floating the valves at a sertain point then hit the pistons and boom chain.

 

Is it possible that the crank snout isn't fully seated against the crank gear, causing lateral load on the chain?

 

Joe, its another thing for me to check, thanks.

 

You would be bending pushrods before the chain broke.

 

How about an oil pump where the relief valve is stuck causing extremely high oil pressure and drag on the cam?

Tom Piper

 

dId you take it apart yourself and see the broken chain ? or is the shop just showing you a broken chain , check the chain alignment yourself or have somebody that has done that work before ... other than the machine shop, too many crooked ones out there !

 

The machine shop took the motor back and (supposedly) fixed it the first time it broke so I don,t think they are crooked or they would not be going to all the trouble to take back the motor and redo it on their dime, but somethings goofy and they need to figure out what it is.
Good Luck Justin, hope it works out. I know your getting frustrated but don,t give up hope.
Besides you have done too many motor swaps now not to see what the combo can ultimately do.
If you need any help give me a call maybe I can swing by after work.

 

We pulled it apart and the chain was broke the first time. I haven't had time to pull this one apart/out yet, it should be out Tuesday night.

 

If you put a stock chain in then what do you expect to happen? An aftermarket one breaks so you think installing the weakest chain possible is the best idea.

 

A stock chain should support the power I'm at right now. My old motor had a stock chain and had about the same power(since this setup wasn't ever tuned to where it should be). Only issue is it will stretch over time(15k+ miles), but I knew that going in. By 15k miles I'll be ready to build something else.

 

People break stock chains on stock motors. I would never run one. The price it cost you to fix the damage the damage from this stock chain would equal several nice aftermarket ones. Its just not worth it to put a stock chain back in.