Chain Guide Wear

[Dynomite]

There is a lot of discussion related to Chain Guide Wear. The longevity of Chain Guide Facings have ranged from 100K miles to well over 150K miles. One case is of interest with Chain Guide breaking up after only 60K miles and that engine is being offered with broken guide at that 60K miles on CF broken guide at 60K miles

1. Background.

The Wear Points on the Camshaft Chain Guides (not the top chain guide in each Cam Cover) are the Top Chain Guide on Drivers Side and Bottom Chain Guide on Passenger Side (inside the Front Cover). Both of these two Chain Guides are Associated with the Drivers Side and Passenger Side Chain Tensioners.



2. How long do Chain Guides Last without Replacing?

Mark has suggested to me that a chain guide should go for 150K miles assuming proper engine oil and engine oil changes are made.

Several have suggested a 100K miles Chain Guide Replacement. Others have said they will go much longer. Others (only three that I am aware of) have broken Camshaft Timing Chains with no particular cause identified. The Timing Chain Failures are Not necessarily associated with failed Chain Guide Facings.

3. Chain Guide Wear can be inspected on the Passenger Side without removing the Engine or Cam Covers.
The Passenger Side Lower Chain Guide Wear can be inspected through the Oil Fill Cap. The two primary Chain Guides wear is the most (associated with the right and left Chain Tensioner - Bottom Right and Top Left). The Bottom Right seems to wear the greatest associated with the Right Chain Tensioner.

The Top Chain Guide attached to the Valve Cover can be seen making sure it is not broken and the Tab is intact.

The Camshaft Chain (passenger side) can be seen resting on the Lower Chain Guide and the Wear on that Chain Guide observed through the Oil Fill Cap. This inspection and verification of Chain Guide Wear (Somewhat inexact but one can get a general sense of the wear by this observation) on the Passenger Side is indicative of Chain Guide Wear on the Drivers Side also as I have observed equal Chain Guide Wear on both sides of the engine (Chain Tensioner associated Chain Guides as the other two Chain Guides usually have hardly any wear at all).



4. Lower Chain Guide Wear Passenger Side.
The Lower Chain Guide on Passenger Side associated with the Chain Tensioner on that side can be seen and with a flashlight and the general condition verified (no broken tip or sides). Using a Bore Scope, the Chain Guide Wear can be observed noting the depth of the wear on each side of the links as noted. Also the center portion of the Chain Guide on which the rollers roll can also be seen. In general, Chain guide wears relatively fast until the rollers come in contact with the Chain Guide. At this point in the Chain Guide Wear, the Wear is extremely slow. One looks for less than a 1/32 inch depth of grooves in Chain Guide Facings where the links ride on the facings. At approximately 1/32 inch depth of the grooves on the Facings the rollers are in contact with the Chain Guide Facing with very minimal wear rate from then on.

[A26B]

As always, good info Cliff.

I take no exception to the longevity of the guide facing in and of themselves, there is another point worthy of consideration.

I would not recommend going into the engine for no other reason than to change the chain guide facings at 60,000, 100,000 or more miles.

However, if I were that deep into the engine for other reasons, I wouldn't hesitate to replace all of the facings at that time. Heat cycles, age and wear all considered, do have an effect on how much usable life is left. The LT5 is not an inexpensive endeavor to work on, especially when it's dismantled to the point where the chain guides can be accessed. Why take a chance on 25 year old consumable parts when the replacement cost for new is only $259.00 fo the entire set?