Timing Chain chain Guides PM

[lakemeadzmonster]

What is the normal mileage and are their signs a timing chain tune-up is due.

So many parts to the system including nylon guides/gear sprockets/ tensioners/ gaskets and I'm probably forgetting other items.

Mine seem fine at the moment but I notice a lot of parts seem almost unavailable and very expensive. What is the best approach to maintaining or monitoring this critical area of the LT5?

[A26B]

The facings for the chain guides are about to get "un-scarce," (2,000 of each guide facing expected soon), and I have a good inventory of gears/sprockets, tensioners & gaskets. I am still working on a supply of chains and expect to have them soon.

The guides themselves never wear out, the sprockets & gears and even chains have a very long life. I've not kept a log, but I think the majority of chain failures I know of were secondary to the primary cause. In other words, something else failed first that in turn damaged the chains.

[Dynomite]

What is the normal mileage and are their signs a timing chain tune-up is due.

So many parts to the system including nylon guides/gear sprockets/ tensioners/ gaskets and I'm probably forgetting other items.

Mine seem fine at the moment but I notice a lot of parts seem almost unavailable and very expensive. What is the best approach to maintaining or monitoring this critical area of the LT5?

I refer questions related to long term wear and potential failures to Marc Haibeck (http://www.zr1specialist.com) or Jerry (http://jerrysgaskets.com/store2/root/)

Marc as much as anyone has seen many degrees of mileage and use and change periods of various engine oils that have a direct effect on wear on the LT5 engine including Timing Chain Guides. Marc did mention to me one time (as I recall) that the timing chain guides will initially wear the two grooves before the rollers actually ride on the guides which would be normal wear in operation. From that point on the guide wear slows down appreciably. Marc did mention also recently that the there is much more concern related to brittleness of the Timing Chain Guide and from that brittleness they will sometimes break off the end clips (This includes the top chain guide facing mounted in the Cam Cover).

At least that was my understanding. I do know 50K miles you will be at the normal operation wear point on the guides. I would guess here....I am not concerned about 75K miles and I would expect 100K miles the guides to still be in serviceable wear condition.

On the other hand......SAM/CH ZR-1 suggests Chain Guides worn out at 90K miles (http://www.zr1.net/forum/showthread.php?p=104206#post104206) It is unclear what engine oil SAM/CH ZR-1 used (or how often engine oil was changed). It is unknown what oil pressure SAM/CH ZR-1 was running which effects the chain tensioner pressure on the Timing Chain Guides.

http://i287.photobucket.com/albums/ll142/dynomite007/Dynomite5/1dd5b6d2-000b-4b7c-b9aa-378c0ddb8fcf.jpg (http://s287.photobucket.com/user/dynomite007/media/Dynomite5/1dd5b6d2-000b-4b7c-b9aa-378c0ddb8fcf.jpg.html)

I would be very interested in what Marc has to say from his considerable experience viewing Timing Chain Guides and Timing Chains/sprockets with a variety of engne hours.

I once asked Marc if forgetting which way the chains ran would effect wear if you installed the Timing Chains backward from initial installation. Again..as I recall Marc did not see issues with that error :D

I am sure others who have removed the front convers on LT5s having over 100K miles will have the best observations for you in this regard. That observation should be coupled with engine oil type/weight as well as engine oil change period and filter used (as well as high oil pressure issues noted).

I did replace the Timing Chain Guides when I had the engine out of the car (50K miles) including the Primary Chain Tensioner Facing (re-setting the Tension for that new Facing). The guides I removed where in great condition but since I had the front cover off and since the guides are really not that expensive given the work of removing the engine :p

I am thinking/guessing that the Timing Chain Guide Facings can be visually inspected with cam covers removed inserting a wireless camera probe down between the camshaft sprockets (using the same camera by which I can inspect the pistons/cylinder walls by removing a spark plug). See Wireless Bore Scope TIPS (http://www.zr1.net/forum/showthread.php?p=191453)

[pantera1683]

The facings for the chain guides are about to get "un-scarce," (2,000 of each guide facing expected soon), and I have a good inventory of gears/sprockets, tensioners & gaskets. I am still working on a supply of chains and expect to have them soon.

This is why you are "the man", Jerry!

[Dynomite]

The facings for the chain guides are about to get "un-scarce," (2,000 of each guide facing expected soon), and I have a good inventory of gears/sprockets, tensioners & gaskets. I am still working on a supply of chains and expect to have them soon.

The guides themselves never wear out, the sprockets & gears and even chains have a very long life. I've not kept a log, but I think the majority of chain failures I know of were secondary to the primary cause. In other words, something else failed first that in turn damaged the chains.

How often do you get a request for Timing Chains (primary or secondary)?
While the wear on a Timing Chain Guide Facing is obvious by direct inspection, how would one determine you have a worn out Timing Chain?

bdw18_123 had a broken Timing Chain on one of his "high Mile Restorations" with an undertermined cause as I recall. That and one other Timing Chain failure are the only Timing Chain failures I could find in the archives so far.

[USAZR1]

The facings for the chain guides are about to get "un-scarce," (2,000 of each guide facing expected soon), and I have a good inventory of gears/sprockets, tensioners & gaskets. I am still working on a supply of chains and expect to have them soon.


Thank you for stepping up and doing this,Jerry. All of us appreciate what you're doing more than you can imagine.

Is there a certain mileage that the guides need to be replaced at? 100K? 150K?

[A26B]

How often do you get a request for Timing Chains (primary or secondary)?
While the wear on a Timing Chain Guide Facing is obvious by direct inspection, how would one determine you have a worn out Timing Chain?

Not keeping track of requests, I would guess 4 to 6 a year on guides & about half that on chains.

HOWEVER, since we haven't had new replacements available & listed in the web store, I would expect that number to double once they are in stock.

The builder tuners are nearly out of guide facings and have been re-using facings that are still useable. Once we have them in stock, word is new engine builds will receive all new guides & chains.

Summary; I think we will probably move 20~25 sets a year.

The LT5 builders can answer this better than me, but I would expect a worn chain to make more noise than usual, due to loose link pins.

Worn out guide facings would accelerate chain wear and make more noise when metal to metal contact occurs, i.e. facing worn through (primarily on the pivot guides. Look for magnetic metal particulate when changing oil. A magnetic drain plug would be ideal to monitor high mileage engines. A magnet on the oil filter would hide it and not give a visible sign.

Preventative Maintenance:
My WAG is by 100,000 miles if no abnormal chain noise is noted before. A better reference would be from the professional LT5 builders who have seen a lot more high mileage LT5's and cam drive system failures than I ever will.

What Inspection/Replacement Entails:
Pull the engine, remove cam covers & front cover. Replace all chains & guide facings, both primary & secondary. Examine sprockets, replace if wear is evident. Replace Cam Sprocket Retainer bolts (4).

Of course, the next question is always "What else should I do while I'm there?" If the compression check you did before removing the engine is good, I would probably replace the rod bearings.

Main bearings are a different story and open up a whole 'nother discussion. Normally, virtually everything has to come apart to visually check the mains. The crank thrust can be easily checked, but bearing surfaces are a different story. The lower crankcase (main girdle) could be removed while the piston/rods are left in the cylinder, then mark the location of the crank before removing so it can be put back at the correct position. If compression & oil consumption were good, the pistons should not be removed or turned in the cylinders.

I think getting LT5 builders involved on this aspect of the discussion would be crucial. I have my opinion, but it's based on old school methods which was before the LT5 era. What I can do is talk to 3 or 4 of them & return with the results.