Camshaft Timing
 

I was doing a valve adjustment tonight and was curious to how much my chain has streched in 310, 000 miles. I have lined the mark on the cam tower and sprocket and it looks like it is between the first ten and the first line before the second ten this is all to the left of the metal post on the crank looking down from the front of the car is this 12.5 degrees and what should it be ? Thanks for any input.

that mark is just there for assembly purposes but some say it does give you a general idea

I know it is not a precise measurement I just wanted a rough idea how bad it has streched or if it is ok?

For positive confirmation, take a photo and post it. It's difficult to determine what you have from the description.

If you do have 12.5 degrees ATDC, you probably should consider a Woodruff offset key to reduce this value. That's quite late.

A proper check should be done using the 2mm intake valve lift on #1 before you make any firm decisions. The procedure is in the DIY section.

I would not chance anything with 8 or more degrees stretch. A chain job isn't that hard for a decent DIY-er. Just don't drop the chain...

I've got about 4* stretch on my engine. An offset cam key and injection timing adjusment got everything back to normal. (And gave me my favorite oil leak at the IP base...)

The last thread I want to here see is "My timing chain broke today"

I've never seen anyone post a thread regarding a broken timing chain without some peripheral component, such as a slide rail or a tensioning rail fail and take out the chain.

Chains don't fail due to elongation.

However, I might agree that changing it is preferable due to the heavy loading of the first two or three teeth on the sprockets.

Can someone tell me how to upload a picture for this topic and I will go take a pictur of the mark.

Just post a reply as usual.

Before submitting the reply, scroll down and hit the button that says "manage attachments."

You can then upload a photo that you have on your hard drive. The software will guide you through it. When finished, close the window and submit the reply. The photo will be in the post. Make sure the photo is smaller than 66K otherwise it won't display.

Here is the picture thanks for the help guys.

Now, that's why we needed a photo.

You've got the cam timing at 2.5° ATDC. Nothing to concern yourself about and nothing needs to be done.

That is great news to here I bought this car at 62,000 at a dallas mercedes dealer and I have done all the maintenance and changed the oil every 2500 miles I was a little concerned my engine might explode because I am driving it 100 miles a day now to work. Thanks for the help

At 302K, my concern is twofold:

1) The condition of the tensioning rail and slide rails

2) The condition of the tensioning spring for the oil pump and the oil pump chain drive.


Both of these items are in questionable condition at that mileage. A failure of either will likely take out the engine unless you are on top of it within seconds.......and.........even then the loss of the chain would take out all the valves and cam towers.

Naturally, there are engines that go 400K on the original hardware. But, some do not.

Brian are these items replaceable without major work?

Well, the tensioning rails and slide rails definitely require some serious work to remove. It's not a Saturday project.

I have not done the oil pump chain drive or the tensioning spring, but, I don't believe that it's too bad a job. The work is done from underneath, however.......not a lot of fun.

Jim Ellington (engatwork) has done a bunch of them, so, ask him for the tips if you decide to do the oil pump.

For the timing chain guides, you'll need the FSM for the proper step by step approach.

Is there any way to check these items with out major disassembly?