So, say ya stick a new chain on, what's the distance between the chain headed up & the chain headed down? I would want to line the chain up so the peaks on the inside of the links are opposite each other & measure the closest point. On my chain it was close to 1/2 ". It has just over 14,000 miles on it.

And you don't think that the pressure of the cam chain will cause the rear guide to straighten back out as the engine is running?

You have both the pressure of the chain and the non-reversing movement of the tensioner involved here.  If the guide flexes back toward its original shape the tensioner will click into a new ratchet position and stay there.  I would guess that when that happens the curve cannot return.

I hope that it is a quick fix that works, but I still believe the chain will always try to follow the path in this illustration.

Well it fired right up and all seems well!  Chain noise is gone and it runs smooth.

Now its time to tune...

I would be reluctant to drill & tap a hole in that casting. I wonder about a different mount for the cam chain tensioner. If it had an offset post instead of straight, seems a bit more of the plunger could be inside it, allowing for more extension before the hole started getting oblonged or risk falling apart. As long as the post was stopped so that the pressure from the tensioner was tightening it sould hold I would think. Since every set of threads can't be the same, the male end would need a set of some sort. I don't know how much faith I would have in a jam nut in a hot oily place with vibration applied.

Aeres wrote on 12/31/69 at 16:00:03:

Well, as long as you've considered all the options, what can I say?

We all take calculated guesses from time to time...just as I'm doing in the other topic.  I suppose the thing to do will be to put a few thousand on it an open it up for inspection before it would have failed anyway.

Savage_Greg wrote on 12/31/69 at 16:00:03:


Thanks Greg.  Given that I had to put that guide on my knee and really put some force on it (75-100 lbs?) to bend it tells me its not going to go any where.  So from where I sit today I am about 99% sure I have this problem licked for my engine.  The shape is now more like other chain guides I have seen for other engines.  In its original shape, the chain doesn't come in contact with the guide except at the bottom 'knee', which seems to me an unusual design.  And I think that it is a flaw.

However, my curiosity may get the better of me.  I'm considering opening it up again just to see how the tensioner ratchet settled in after having run the engine for a bit.  I can try to take some measurements of the separation between the up and down sides of the chain as was previously suggested.  This will tell me if there were any quick changes from the config where I left it.

For me, the thought of drilling and tapping the case to add another component to this timing system is really unnecessary.  I recommend trying this bent guide technique, and only if that fails, then consider something more radical.

If I decide to open it up I'll take a pic of the tensioner with the used chain and post it.  And I'll let you know what I find.

So I couldn't resist looking at it after it ran a bit.  As you can see in the pic below, the tensioner has settled in to a good position, even though the chain is a used one and a bit stretched but still well within wear limits (has about 17k miles on it).



The measurement now is exactly 12.0mm from the plunger shoulder to the face of the tensioner body.  The space between the two chains is in the neighborhood of 18mm or about 0.7 inches.

In the photo below I am comparing the old plunger with the new one to illustrate how much of the plunger is still inside.  It looks like over half the rack is still available to the ratchet.  



This plunger won't come out unless the chain lets go completely.

So this is great from my perspective.  I feel confident this will last so I will button it up and run it for several thousand miles and check it again.

I'll keep you posted...

So far so good then.  I did notice that my guide still has a small curve to it.  Maybe you found a good quick fix.

Put a couple thousand on it and check again?