High wear on timing chain sprockets 350zHR (cam gears)

[pgs]

Hi mates,

 

My mechanic is changing the oil gallery gasket due the well know low oil pressure problem on HR engines. As the front cover is removed and the engine has 230.000 km, he check the primary chain. It is stretched. So he remove the camshaft sprockets in order to change all 3 chains plus guides plus tensioners.

Then he realizes a very high wear on timing sprockets (4 cam gears plus crank gear). I didn’t make photos yet, but the wear are similar to the photographs attached at the botom of the post found on the net

 

The wear mark are simetrical on both sides of every teeth (if due to chain tension, it should be not simetrical), the 3 central plates of the chain seems to make wearing marks on the sprockets with a depth something between 0.1 and 0.3 mm. The marks are smooth without metal burrs.

 

Surprisingly, if search in google images the part nº of the sprockets (13025-JK20B, 13025-JK21A and 13021-AL51A) you can see many of the new sprockets sold also have this marks from factory (but is difficult to see if are only brightness differences or the marks are really deep).

This 4 sprockets are very expensive (2000€) and the Workshop manual said that if you change the exhaust sprocket you have to change also the Variable Valve Timing Cover (because the magnet retarder brake/friction pad I suppose), this is 1000€ more

 

So, the questions are: have the OEM sprockets this marks on the teeth when new?

Is usual have to change the timing sprockets in this engines?

 

Thank you very much for the help

 

Edited October 28, 2018 by pgs

[ZMANALEX]

If this was mine I would not replace the sprockets as it is not cost effective to do it as per the book.

The answer to your question is that these marks are on new sprockets.

I would however definitely replace the crank sprocket.

These are the main components  that I would replace:

 

 

 

[pgs]

Thanks, the front timing case gasket kit is already bought and timing kit is in process including crank sprocket.

8 hours ago, ZMANALEX said:

The answer to your question is that these marks are on new sprockets.

Are you completely sure about it?

In the image you post, the crank sprocket does not have the marks…

[ZMANALEX]

1 hour ago, pgs said:

Thanks, the front timing case gasket kit is already bought and timing kit is in process including crank sprocket.

Are you completely sure about it?  YES

In the image you post, the crank sprocket does not have the marks… CORRECT

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