A friend had a problem with his LT1 stock timing chain breaking twice. The engine has only cam and porting. His engine drove about 20 miles then had a broken timing chain. It happend twice.

Any idea of what would be the cause? What should he do before putting a new timing chain and going through the same problem again.

 

something may be out of balance throwing the chain off, the only other thing i can think of is the chain itself may not be lined up correctly

 

Stock chain with a bigger cam for one. Go with cloyes double roller or the LT4 EX duty.

 

Just a thought because I have heard of it happening before. Do you have an under-drive crankshaft pulley? If you do be aware that there are two kinds of pulleys. Some like the Fluidamper replace the stock harmonic balancer. Others, the cheaper ones, require you to use the stock crank pulley and the new smaller under-drive pulley. Basically you just put the new pulley between the stock crank pulley and the crank hub using longer bolts. Just make sure you have some sort of harmonic balancer pulley on there.

 

What he said.

 

Yeah most times a timing chain breaks is because the two gears are not lined up and the chain has a side loading.

Bret

 

No underdrive pulley. It has cc 306. Stiff springs and 1.6RR.

Could it be that the stiff springs cause strain on the timing chain.

 

Well, I think we found it. After double checking, the guy has put the underdrive pulley long time before the cam and porting and he didn't put back his stock crank pulley.

Because he had his rev limiter at 6000RPM, he had no problem. Now with porting and cc306, his rev limiter is at 6500RPM. and he is starting to break his chain. At least this is what we think maybe the cause.

He is going to remove the underdrive pulley and put back the stock pulley and see if it stops breaking the timing chain.

 

Make sure he puts the stock alternator pulley back on as well.

 

Sure. Thanks.