Upper Cam Chain facing failure

[LGAFF]

Opened my oil filler cap to find the upper cam chain face had broken; I think this happens on cold start due to so chain whip or slack; article from mark below


http://i134.photobucket.com/albums/q115/lgaff/IMG_0082.jpg (http://s134.photobucket.com/user/lgaff/media/IMG_0082.jpg.html)

http://www.zr1specialist.com/HAT%20Web/articles/Upper%20Camshaft%20Chain%20Guide%20Facing%20Failur es.pdf

[LGAFF]

I did get to check my cam regrinds look fine

http://i134.photobucket.com/albums/q115/lgaff/d246bd31-f48c-42b6-a080-443f6b315917.jpg (http://s134.photobucket.com/user/lgaff/media/d246bd31-f48c-42b6-a080-443f6b315917.jpg.html)


http://i134.photobucket.com/albums/q115/lgaff/33c6043f-2c1a-456b-bfa2-775b78b5ca9c.jpg (http://s134.photobucket.com/user/lgaff/media/33c6043f-2c1a-456b-bfa2-775b78b5ca9c.jpg.html)

[Dynomite]

That failure is a bit strange and I assume rare. You and Marc have not stated a cause or defect other than Chain slap on cold starts. That seems a bit scary and could happen to anyone. A failure you apparently cannot hear. Any more information on this type failure and possible contributing causes would be of interest.

I assume the top of the lifters showing what appears to be wear without the lifter rotating is actually a reflection of the Cam? The cams look in great shape. How many miles on the regrinds? Who did the regrinds?

The Lifters are rotating?

[LGAFF]

Yes thats a reflection......7-8K on the cams, they are my own regrinds.


As for the failure I am not sure what caused it other than chain slap....the engine was very cold and had sat for some time. I only caught it because I opened the oil cap.

[Dynomite]

Yes thats a reflection......7-8K on the cams, they are my own regrinds.


As for the failure I am not sure what caused it other than chain slap....the engine was very cold and had sat for some time. I only caught it because I opened the oil cap.

Very good regrinds there Lee :thumbsup:

You are scaring the Fast Boys from Ill on those COOOOLD Mornings wanting to fire up the ZR1 :p

I think you have a photo of what that broken chain guide looks like through the Oil Fill Port?

Good that ONLY the Right Facing is apparently failing (of 7 Marc Describes except one on the left) as all those top chain guide failures on right side can be see by removing the oil cap. Do I understand that correctly???

I also see that all those failures were discovered removing the cam covers for maintenance or rebuild and were not noticed by inspection through the Oil Cap??? Except one chain guide failure was only noticed after it resulted in broken timing chain.

Great Information on what I assume is a very rare but possible failure. And a failure very easily observed through the Oil Cap..

[XfireZ51]

Pete found something very similar when we pulled the cam covers to do the exhaust cams on my motor. The peg that holds the chain guide had broken along it to float. No damage but...
And yes mine was passenger side but I'll confirm w Pete.

[Dynomite]

Pete found something very similar when we pulled the cam covers to do the exhaust cams on my motor. The peg that holds the chain guide had broken along it to float. No damage but...
And yes mine was passenger side but I'll confirm w Pete.

Are you still talking about the top chain guide or one of these?


http://i287.photobucket.com/albums/ll142/dynomite007/B%20Engine%20LT5/SChainGuide_zps8052c04a.jpghttp://i287.photobucket.com/albums/ll142/dynomite007/B%20Engine%20LT5/SChainGuidesonly_zpsf0997ed4.jpg

If top chain guide you are talking about the lip that keep the guide in place on each end of the guide probably similar to what Lee experienced??

[XfireZ51]

Same as Lee's. It was floating loose at the front of the cam cover.

[Dynomite]

Same as Lee's. It was floating loose at the front of the cam cover.

This is what the upper Passenger Side (Right) upper chain guide should look like looking into the Oil Fill Port on Passenger Side Cam Cover. And like Marc suggests, it is the right side (Passenger Side) that is the issue (A very rare issue). Upper Camshaft Chain Guide Failures (http://www.zr1specialist.com/HAT%20Web/articles/Upper%20Camshaft%20Chain%20Guide%20Facing%20Failur es.pdf)

You can feel the black tab with your finger.

If the black tab is not gripping the holder or if the black tab cannot be seen.....oh well....you are experiencing a very rare issue :p

Upper Chain Guide Improved Facing by Marc Haibeck (http://www.zr1specialist.com/HAT%20Web/products/upper%20chain%20guide.htm)

http://i287.photobucket.com/albums/ll142/dynomite007/Dynomite12/Chain%20Guide%20Facing.jpg

Opened my oil filler cap to find the upper cam chain face had broken; I think this happens on cold start due to so chain whip or slack; article from Marc http://www.zr1specialist.com/HAT%20Web/articles/Upper%20Camshaft%20Chain%20Guide%20Facing%20Failur es.pdf

http://i134.photobucket.com/albums/q115/lgaff/IMG_0082.jpg

[Franke]

After reading Marcs article, I'm thinking this part is subject to failure easily since its just a plastic tab that holds it in place on the guide holder correct? As Marc says it just clips on. He also shows that he manufactures the part with a modification to help relieve stress at the tab attaching points. It should be easy to see according to Lee's pic and Marc's article. I looked at mine and I don't see the black plastic retainer tab as pictured in Lees post so that being said I wonder how many Z's have this problem? My car has 56K on it and I'll probably be contacting Jerry and Marc for some parts. Maybe a kit for replacing this plastic guide facing would be a good idea. :)

[Dynomite]

After reading Marcs article, I'm thinking this part is subject to failure easily since its just a plastic tab that holds it in place on the guide holder correct? As Marc says it just clips on. He also shows that he manufactures the part with a modification to help relieve stress at the tab attaching points. It should be easy to see according to Lee's pic and Marc's article. I looked at mine and I don't see the black plastic retainer tab as pictured in Lees post so that being said I wonder how many Z's have this problem? My car has 56K on it and I'll probably be contacting Jerry and Marc for some parts. Maybe a kit for replacing this plastic guide facing would be a good idea. :)

I checked two LT5s today (a 1991 and a 1990) and both look as shown in the photo below.

Are you saying you do not see this black tab at all in your
LT5? What do you see there? A slot where the tab should be?
Do you see the Chain Guide Facing Holder in your LT5?
Could you take a photo of what you see inside your LT5 Oil Fill Port?

http://i287.photobucket.com/albums/ll142/dynomite007/Dynomite12/Chain%20Guide%20Facing.jpg

[Franke]

I checked two LT5s today (a 1991 and a 1990) and both look as shown in the photo below.

Are you saying you do not see this black tab at all in your
LT5? What do you see there? A slot where the tab should be?
Do you see the Chain Guide Facing Holder in your LT5?
Could you take a photo of what you see inside your LT5 Oil Fill Port?

http://i287.photobucket.com/albums/ll142/dynomite007/Dynomite12/Chain%20Guide%20Facing.jpg

I see what looks like a tan piece of some sort not black plastic. Pictures are attached. I was able to move it just a bit with my finger so it maybe be just a tab color issue. I could use yours and others opinions as I would hate to pull that cam cover to find out it is ok.

[Dynomite]

I see what looks like a tan piece of some sort not black plastic. Pictures are attached. I was able to move it just a bit with my finger so it maybe be just a tab color issue. I could use yours and others opinions as I would hate to pull that cam cover to find out it is ok.

You are fine....your facing is intact and in good shape as we cannot determine Facing wear but you DID determine it was secure to the Facing Holder.

My tab is blacker than tan and yours is tan/black....that facing is normally tan. You scared me for a minute thinking this issue is Not so Rare after all. I still say the issue is very rare. :handshak:

http://www.zr1.net/forum/attachment.php?attachmentid=4387&stc=1&thumb=1&d=1434547680

Put your Oil Cap back on and take a drive ;)

[Franke]

Sorry to scare you Dyno as I was scared too. It seems that there may be somewhat different tab colors then. When I put my video scope in there it was definitely a tan piece that I saw so naturally I was a bit worried that the "black tab was gone". Looking at Marc's article I could see how the plastic piece attaches to the tan colored metallic holder so I thought that tan piece I saw was the holder rather than the plastic guide. Thanks for clearing this up for me. You are one of the LT5 guru's here. No worries now. :)