Checking Timing Chain Stretch

[Jetaway]

A couple of probably obvious questions for many, but not for me.

I've looked in Autocar, Chilton's, the FSM, and other assorted manuals but cannot determine the answer to what seems to be a simple question:

1) To check for timing chain stretch is it necessary to remove the front cover, or can it be done by removing the valve cover?

2) If the above is yes and the chain is stretched, is it necessary to remove the front cover to adjust for stretch?

Chris

[siteunseen]

Here's what I've read about that, never done it though but there's info in the archives about it. You can pull the valve cover and shine a flashlight down the passengers side of the chain to see how far your tensioner is pushed out. You're not supposed to see any of the metal on the plunger or very little. A 1/4 inch would be the max I'd think, 1/2 inch and you need to move the sprocket to the next number. here's something to look at, http://atlanticz.ca/zclub/techtips/timing/mechtime.html

[Zed Head]

There's a procedure in the Engine Mechanical chapter of the FSM also, showing an illustration of the notch and groove at the camshaft that atlanticz pictures show. Those two resources together should allow you to check, without removing the front cover. You can also adjust for stretch without removing the front cover as long as you wedge the timing chain and tensioner before you remove the sprocket.

[djwarner]

I think what Jetaway is asking is "How do you decide which setting to use, 1,2,3 or is it time to buy a new chain?"

From what I can tell, you set the crank at TDC; set the Cam with the alignment pin at 12:00 o'clock; and figure out setting is closest to right.

Since we are talking about a few degrees here or there, is there a more precise method?

[siteunseen]

I think what Jetaway is asking is "How do you decide which setting to use, 1,2,3 or is it time to buy a new chain?"

Where did you get that quote from? I didn't read that in his post.

[djwarner]

Sorry, my post was not intended to be a direct quote, but rather my interpretation of his first post. If he wasn't asking, then I guess I will.

[Jetaway]

Where did you get that quote from? I didn't read that in his post.

Prophecy. While it is true that I didn't ask specifically about how to tell if the chain needed replacement, I probably would have on a follow-up.

I asked about it because if adjusting the timing required pulling the front cover I would just go ahead and install a new chain et al. as I've put 60,000 miles on it since buying it six years ago. With a likely 140,000 on it at the time, the timing chain, had it ever been replaced, was likely replaced many miles earlier. But since I can check it, and if needed and not already on the 3rd peg, adjust it, while adjusting the valve gaps, I've already paid for part of the labor, so to speak, so might as well make the adjustment then.

Thanks for the responses.

Chris

[Zed Head]

Make sure that you turn the engine in the normal rotation direction when setting the pointer on zero, or put a wrench on the sprocket bolt and back it up to tighten the "tight side" of the chain (the left/driver side). There's enough play in it with no oil pressure on the tensioner, to get your marks misaligned if there's slack on the wrong side.

[siteunseen]

Sorry, my post was not intended to be a direct quote, but rather my interpretation of his first post. If he wasn't asking, then I guess I will.

No sir! No need to say that. I apologize for my comment, it was totally uncalled for. I was trying to be funny and failed miserably, I regret it. Dad-gum Bud Lites. Again, I'm sorry.

[Jetaway]

Make sure that you turn the engine in the normal rotation direction when setting the pointer on zero, or put a wrench on the sprocket bolt and back it up to tighten the "tight side" of the chain (the left/driver side). There's enough play in it with no oil pressure on the tensioner, to get your marks misaligned if there's slack on the wrong side.

This is a good thing to know. Thanks!

Chris

[Jetaway]

It is done.

Being a tad bit nervous about the process, I grabbed a friend of mine, "The World's Best Mechanic" -- my title, not his -- for consultation. Good thing too, because while I had the basics down -- marking the timing chain, finding the marks, securing the chain, it took one hell of a lot of torque to get the camshaft gear bolt off. We ended up using a 2 and a half foot long pry bar, laid across the bolt of the cam bearing shell through the gear and a two-foot long socket wrench on the bolt to get it off. I pressed down on the pry bar and was damn near lifted off the ground before it finally broke loose. The spec's on it are 40 ft./lbs +- 10% and a guess, and believe me, Greg would have a very good guess, is it took a good 200 ft./lbs to break that sucker loose.

As I suspected the chain was loose. Boy Howdy was it loose. The gear was in the "1" position and I moved it to the "3" which put the notch on the cam gear right in line with the oblong mark, not to the right of it as it should be after adjustment. So, we're talking 10 degrees of stretch in the chain. Figure its good for another 10,000 miles and then time to replace the whole assembly. Not surprisingly, after driving around to warm it up, every valve was "tight," and they really felt tight by the same amount. After adjusting the valves, and what the hell, as long as I adjusted the valves, the carbs, a very different feel to the car. It could hold a smooth idle at 550 -- 600 rpm while before it would need 700 -- 800 rpm to be somewhat smooth and trying to go any lower risked a downward spiral to stall.

About the only tip I can add is that the FSM is much clearer on where to locate the oblong mark. Maybe if I didn't have to clean off decades of engine build up that was pretty much indistinguishable from a metal finish, I could have found it using the diagram in Chilton's, but even then I have my doubts.

I'm still a little amazed at how much force it took to break loose the gear nut. If it had any effect, the engine's rotation would serve to loosen it, not tighten it. Either it had been replaced at some point by an over-enthusastic mechanic, or more likely, 42 years of close company and likely 1000s of heat / cool cycles melded the two together.

Thanks for the tips!

Chris