On a more serious note: timing chain talk

[73MB280SEL]

Howdy,

While under the hood I decided to pop the valve cover and inspect the timing chain. I have measured the stretch twice and it comes up 4 - 5 degrees, which is pretty stretched. I have no idea when it was last replaced, but visually it is somewhat worn (polished links, rollers starting to show polish). The upper guides that I can see look black. Today, I scratched them and they don't look at all white underneath. Is it really that stained or did they make some that were not white.

Sure does look like the one going from the right hand camshaft to the valley has got a couple of cracks in it.

What's required (tools, parts) to do this? Do I need to do more than just the upper guides? My car could use a valve job and a right side cam. I've got the clearence adjusted, but it smokes a little. Is it time or should I roll another chain in and do the heads when they really need it?

I know this has been discussed to death, but some input would be helpful.

Sholin

[MikeTangas]

Sholin,

To the best of my knowledge the guides on the 4.5 should be aluminum, perhaps that is why they don't look white when you scratch them.

I just did chain and guides on the 560, I'm sure the 4.5 will be about the same. If you do the guides, you will have to remove the steering pump and attachment plate as well as the alternator and bracket and the distributor too, just to access the guide pins. If the guides are in fact aluminum, you shouldn't have to replace them for hundreds of thousands of miles.

As far as rolling in a chain it's and easy job. Pull the fan so you can access the crank nut from the top side, pop the valve covers and all spark plugs. Roll her around to TDC and check the timing marks at crank and both cams. A chain guide is handy for rolling in a new one, but can be done without. Without the guide, you have to tie wrap the inflow of new chain and the out flow of old chain to the cam at the alternator side of the block. Stuff a rag in the chain box of the head, grind off the pins for one link, separate and attach the new chain. Be sure to remove the rag before rolling in the chain.

Roll the chain in, keeping both infeed and outflow in contact with the cam. When you come to the end, you'll find the new chain appears to be at least one link short, don't worry. Now remove the old tensioner, you'll gain the link back attach the chain ends and install the new tensioner. Note: the new tensioner will have much more tension than the old one and will be difficult to press in close enough to the block to install the bolts. Eat your Wheaties, you'll need them .

Once the chain is in and the ends are attached, roll the engine by hand through at least two complete cycles to be sure everything is right, every time #1 comes to TDC on a compression stroke all the marks should line up. I noted that the crank makes 6 revolutions for one complete turn of the chain.

Hope this helps.
Forgot tools/parts:

Chain, tensioner and valve cover seals are the only parts you need to just do the chain.

No fancy tools other than the chain guide if you need to use it, and the pin puller if you do the guides, but you can make your own pin puller out of a 14mm deepwell socket, a long 6x50 (??) bolt and a stack of washers. I used a dremel with a grind stone to grind the link pins.

If you replace the cam, remember you need to replace the other so you have matched set.

[73MB280SEL]

Mike,

Thanks for the writup.

I just looked at is and: The curved guide (tensioner side) is the original steel one. The M116/M117 book shows an updated aluminum version. Both shown have plastic soles, but the aluminum one is replaceable.

I swear the upper guide rail is aluminum with a black plastic sole. The sole may be cracked, but looking closer it may also just be scored. I really think these are old, so I'd better dive in.

Both soles appear to be black plastic.

I guess I've got a question: Where do you break the old chain at? On the tensioner side or the other side of the cam? There is quite a bit of tension on the tensioner side. If I break the chain, isn't this going to rotate the cam quite a bit?

Tell me more about attaching the new chain to itself once it's rolled in. Do I need to peen the end of the link? How much?

As far as camshafts, the right side looks pretty scored. I can tell that some of the valves had not been adjusted for a while as they were polished all the way around the lobe. One lobe is scored enough to (I guess) wear through the hardened layer. It creates a ridge at the trail edge of the lobe which affects running and idle vacuum. The left site looks much better but you are right, replacing both would be the smart thing to do. I guess then I have to worry about cam tower bearings and cracks. I also wonder about exchanging them for rebuilt heads (providing these would come with cams). I'd hate to buy heads, though, just because of a little smoke on startup. My car really doesn't burn enough oil to matter between changes.

Thanks for the info.

Sholin

[MikeTangas]

If it smokes just a little at start-up, that sounds more like valve stem seals.

Any way, I broke the chain on the tensioner side (right head) a little left of 12 o'clock. Once you grind off the pin ends, nothing will happen, you will have to pry off the link plate then push the pins toward the rear, lift the front links, pull the center plate, basically work the link pin out. The chain will be pretty much locked in the sprockets. If you feel better, you can tie wrap the chain on both sides of the cut link prior to working out the pin.

Attach the new chain to the old with the provided link (might be a clip type - was on the 560). If you don't use a guide or the tie wraps, there is a very real chance you'll jump time. What seems to happen is as you come rounfd to TDC, if the out feed of old chain isn't pulling on the sprocket, the cam will jump clockwise, about one tooth. If that happens you have to very carefully lift the new chain off the sprocket, maintaining tension and back the cam CCW one tooth. Sounds scarier than it is trust me I know.

Don't know what the replacement master link is like for the 4.5, for the 560 I got a dual "C" clip master. I called two dealers and talked with the local Indie, trying to find a crimpable type. Apparently the dual "C" clip is acceptable now a days. Just be sure to mount the clips with the open end of the C trailing, and that they audibly click when you press them on.

The curved guide is the tensioner guide. I don't think you want to replace that one, requires the front timing cover be removed. You want the upper guides (3), one in the right head and two in the left. I don't know if the steel or aluminum guides are still available, you might end up with the all plastic ones. If that is the case you might also have to change guide pins, not sure on that though, check with the pros.