Timing chain replacement

[DavidB]

What is the expected life of a 71' 240 timing chain? I have about 140,000 miles on the engine. Any other comments on this.

[ChrisA]

How's the car run? My L24 went about that many miles and the valve stem seals let go. The chain looked good but I replaced it anyway. I've heard about chain stretch and all but never seen it on an L series motor. I've run Z cars for 20 years and never had a failure. I have heard that if the oil fed tensioner inside the front cover fails then you'll have trouble.

Much luck,

Chris

[TomoHawk]

What keeps the tensioner from failing? To me, that's the biggest thing to worry about.

thx

[Bambikiller240]

Originally posted by DavidB

What is the expected life of a 71' 240 timing chain? I have about 140,000 miles on the engine. Any other comments on this.

I replaced mine at 155,000 miles. It was still working well, and not overly stretched, but I was replacing parts as preventative maintainance and it just made sense to me to replace the tensioner, gears and chain at the same time. Relatively minimal cost considering the damage that could be done if one of these items fails. Peace of Mind!

[MikeW]

Originally posted by ChrisA

I have heard that if the oil fed tensioner inside the front cover fails then you'll have trouble.

This kind of trouble ...

[TomoHawk]

My 280Z only has 108k miles. I should be Ok for a while...

[beandip]

David , at 140K you should be fine , in the future if and when you pull the head for a valve job or if you are going to rebuild the engine , I would then replace the chain and sprokets as well as the tensioner. To answer the question it should go to 200K miles. Alot depends on how hard the engine is pushed or has been pushed. If abused anything can happen. :classic:

[Zedrally]

Originally posted by MikeW

This kind of trouble ...

Was this attributable to chain strech, tensioner failure or did the cam sprocket slip?

MOM

[Bambikiller240]

Originally posted by Zedrally

Was this attributable to chain strech, tensioner failure or did the cam sprocket slip?

MOM

It wasn't my engine, but..........

From the looks of the VERY deep grooves in the tensioner "shoe", I'd say it's likely that the tensioner quit "tensioning".

[MikeW]

Originally posted by Zedrally

Was this attributable to chain strech, tensioner failure or did the cam sprocket slip?

I had to replace the head gasket and apparently failed to sufficiently wedge in the block of wood holding the tensioner in place. When putting things back together I had trouble getting the cam spocket back on and had to use a bit of leverage to coerce it. This apparently weakened the tensioner because a few days later while driving everything went bad in a hurry. It appears as though the tensioner broke which in turn caused the chain to slip.

Keep in mind that I was a dumb teenager at the time (before helpful intenet resources) and only figured what I had done wrong after the fact.

[MikeW]

Originally posted by Bambikiller240

From the looks of the VERY deep grooves in the tensioner "shoe", I'd say it's likely that the tensioner quit "tensioning".

Bingo. Here's a better shot.

[Zedrally]

So we could conclude that it was not the chain or tensioner or cam sproket that caused this directly.

In fact, it was in-correct assembly and no chain or tensioner replacement was neccesary.

In my opinion chain strech would cause mis-timing which could be adjusted on the cam sprocket, obviously there must be a factory life, and this is what the original question was.

Anyone with a FSM handy?

MOM