timing chain

[nissan720]

why did nissan go from a double roller timing chain found in the z24 to a single roller found in the ka?and the guide on the ka is plastic,the side next to the manifold.on the z24 iis some type of hard urethane bonded to the metal guide?And did the lb20 have a acess hole for the chain tensioner? i would think that nissan would have stuck with the double roller chain and the bonded urethane in the ka motor? i guess that they were making them to good and not selling enough parts or theying to do it cheaper

 

[datzenmike]

They were over engineered to begin with. Never seen a broken one or one worn out for that matter. In fact there is a provision for removing 4 degrees of wear induces slack. 

 

I've pulled an '89 KA apart to find the timing chain guides pristine.... until the pan come off and almost all the plastic guide was in there. It all comes down to making a part that wears out with the engine. If the part outlasts the engine you're loosing money.  A good idea would be to replace the timing chain and guide every 100K