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://www.zr1specialist.com/HAT%20W...20Failures.pdf

[LGAFF]

I did get to check my cam regrinds look fine

[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]

Originally Posted by 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.

Very good regrinds there Lee

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

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]

Originally Posted by 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.

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




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??

[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]

Originally Posted by 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.

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?

[Franke]

Originally Posted by Dynomite

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?

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.