220/8 W115 Timing Chain
 

Hi All,

I'm looking for your opinions on changing the timing chain on a 1970 220 with approximately 100k miles. There is no chain noise on startup, and oil pressure always goes up very fast, but I still wonder about eventual chain failure.

I asked my local shop that specializes in vintage MB, they told me unless I'm getting noise they wouldn't recommend changing out the chain. They reported that the chains on these models are very reliable, and don't necessary need to be replaced. They did suggest that the tension rail could/should be inspected, probably at the same time as a valve adjustment.

So I wonder, is he right, is the chain reliable even at 100k? What should I look for in a worn tension rail? And should I also look at the straight guides?

What are the indicators that would indicate it's time to replace the timing chain?

All thoughts much appreciated. Cheers!

Typically, the longer V-8 chains require frequent changing. The shorter chains don't. To check, align your timing marks on the crank and the camshaft front bearing. Check for the offset due to wear, commonly called stretch, and note the difference. The guides may need to be replaced. The pins need to be removed, the guides replaced and new pins inserted. If the offset is still excessive, the chain will need to be replaced.

Check it out, post some pictures and we can help you.

I agree with your local shop. Worry about the chain after another 100K miles. The guides are going to wear much faster than the chain. And as long as the chain groove is not down to the metal part of the guides and rails, you´re OK. On most MBZ motors, up to 4 degrees of chain stretch is acceptable before chain replacement or woodruff-key installation on the cam sprocket.

Thanks for your replies--I will post some pictures of guide wear for reference. Cheers!

How difficult is it to replace the w115 pins/guides? Is it a very tricky job? Do you need special tools?

It's been a few years since I replaced the guides on the M115 but I seem to recall you need to split the chain to replace the top guide. The pins are simple slide pins and can easily be removed using a bolt and slide hammer although I've heard many people removed them using a stack of over sized washers instead of a slide hammer.

To access the lower rail pin you need to pull the dampener I believe. It's easiest to pull the radiator for access.

Why are you replacing the rails? If you don't have chain stretch there's no need.

If you're bored and looking for something to do then c'mon over to my place and you can help me sand down my 250C for paint prep. Maybe give alabasi a ring and help him with one of his 50 projects.:D

Thanks Mike - curious more than anything. I still have that nagging clatter sound at times that seems to stop if I turn the car off, then turn it back on. I can't see to be able to isolate it. My chain does not seem to be stretched, I did take note comparing the crank position to the mark on the cam and it seems ok. Wonder if my chain tensioner is not functioning correctly/sticking - could my chain be loose, then when I stop/start the tensioner does it's job?

Anyway, I have more projects than I know what to do with, so I will pass on sanding!