Chain guides

[ZRXMAX]

How many pieces need to be removed before all 4 chain guides can be removed and replaced?
1. Do either cam covers need to be removed?
2. Does the idler sprocket need to removed?

Is their a procedure for the chain tensioners to be handled in a certain manner? Do you have to remove them? Pin them?

I am looking at pages 6A2-73, 74, 75 in the 91 GM manual.

[A26B]

How many pieces need to be removed before all 4 chain guides can be removed and replaced?
1. Do either cam covers need to be removed?
2. Does the idler sprocket need to removed?

Is their a procedure for the chain tensioners to be handled in a certain manner? Do you have to remove them? Pin them?

I am looking at pages 6A2-73, 74, 75 in the 91 GM manual.

The engine needs to be removed, primarily because the harmonic damper needs to come off in order to remove the front cover, BUT also makes the rest of the job much easier.

Yes, the cam cover need to be removed as well as the camshafts. There is not enough room to pull the guides up & out with the cam chains in place on the camshafts & the cams in place.

I have always removed the cylinder heads before removing the chain guides, having never tried to R&R the guides with heads in place, but I think you can.

Yes, Idler sprocket has to be removed to access guide bolts.

Tensioners require no special handling to remove them, but must be re-set (cocked before installation & release(fired) before engine start. The tensioner housing & tensioner are specific LH & RH & must be properly oriented. Resetting the tensioners is a tad tricky. You can send them to Marc or Corey to be reset. If you need new ones (not too likely) they come already cocked.

New Cam Sprocket Bolts are required. DO NOT reuse them.

[A26B]

Here's a better photo of what it looks like behind the front cover.
https://store-nkg90o.mybigcommerce.com/product_images/uploaded_images/chain-guides-smallsize.jpg

[ZRXMAX]

Thank you for that good information Jerry! My motor made it about 175K before this issue came to my attention. It was running as good as it ever has and this came as a surprise.

It looks like I have some work to do. :)

[Dynomite]

What made you decide you need new chain guide facings? What were the issues?

Just wondering what to look for ;)


Sent from my iPhone using ZR-1 Net Registry (http://r.tapatalk.com/byo?rid=90383)

[ZRXMAX]

Wasn't a good diagnosis on my part. The chain sound was on the passenger side was not particularly bad to begin with. Then, it went away. Then about 2 weeks later it came back at a level that was 3 times as noticeable.

My best guess now is that the tensioner has failed. I will be removing that first for inspection to determine if that is the problem. If it is, how do I do I reset ( **** ) the next tensioner before installing it?

[Dynomite]

My best guess now is that the tensioner has failed. I will be removing that first for inspection to determine if that is the problem. If it is, how do I do I reset ( **** ) the next tensioner before installing it?

Post 26 - Setting/Installing the Chain Tensioners Tricks (http://forums.corvetteforum.com/c4-zr-1-discussion/3005470-tech-info-lt5-modifications-rebuild-tricks-500-hp-2.html#post1581302489)

Pay particular attention on releasing the Chain Tensioner once installed.

g. Insert a small punch positioned through the hole (removed allen head plug) on the top of the tensioner locator housing. Tilt the punch to the side making sure you are not punching the check valve on top of the barrel of the tensioner plunger. Give the punch a sharp tap with a small hammer.


Here is an original from Ben
I remembered seeing a really good write up over at the "other" forum quite awhile ago (which we again can't link to, I thought that was fixed? :rolleyes: ) on how to reset a timing chain tensioner with some good instructional pictures. It was done by someone with a forum name of ZR1 at that "other" forum. I decided to go looking for it since I need to reset my tensioners. Resetting timing chain tensioner TIPS (http://www.zr1.net/forum/showthread.php?t=14693)

The Other Trick is to use a Chain Tensioner Unloader that Phil Machined which is large enough such that it barely fits in the Chain Tensioner hole and does not damage the check valve.

Let us know what you find :handshak:

[ZRXMAX]

I have the passenger side tensioner out and can't see anything out of the ordinary in so far as wear goes. However, in an attempt to reset it... it won't reset. I tried it twice and neither time would it hold at the full reset setting.

Is this a clue to what determines if it has lost tolerance and is no longer usable?

Do you think this might be what was causing the loud chain sound up until around 3000 rpm before it would go quiet?

[Dynomite]

I have the passenger side tensioner out and can't see anything out of the ordinary in so far as wear goes. However, in an attempt to reset it... it won't reset. I tried it twice and neither time would it hold at the full reset setting.

Is this a clue to what determines if it has lost tolerance and is no longer usable?

Do you think this might be what was causing the loud chain sound up until around 3000 rpm before it would go quiet?

I think you just have to keep trying to reset as it sometimes takes several tries.

Marc suggests the following:

"I believe that GM recommends a new tensioner, rather than compressing the tensioner because the process might be too difficult for some people to implement. It's a delicate process that if done incorrectly can permanently damage the tensioner or cause major engine damage."

Chain Tensioner Compression (http://www.zr1specialist.com/HAT%20Web/services/tensioner%20compression.htm)

Marc will reset the Tensioner for $25 and tell you if anything wrong with Tensioner......but with 175K miles......
maybe time for new Chain Guide Facings from Jerry.