Or not? How much stretch is acceptable and if you had the valve cover off on your 1983 300 TDT and a new chain ready to go, would you replace it now or is 5 degrees of stretch no real big deal?

I would and eliminate worry.

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1999 w140, quit voting to old, and to old to fight, a god damned veteran, deutschland deutschland uber alles uber alles in der welt

That's kinda where I've been leaning! I had the head at a machine shop less than 1000 miles ago and didn't bother to replace the chain then because it looked OK to just drive carefully around town close to home to let everything "settle in."

I'd worry more about the guides, rails & tensioner than I would about the chain.

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1984 300SD Turbo Diesel 150,000 miles

OBK member #23

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I did replace the tensioner spring and the slipper foot when I had the head off. The upper guide rails have been replaced as well.

Have you got an offset key in the cam sprocket or the "normal" one. I have a 2.5 degree offset key here which would fix your problem if you want it...

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz

How are you measuring it?

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1995 E420 Schwarz
1995 E300 Weiss
#1987 300D Sturmmachine
#1991 300D Nearly Perfect
#1994 E320 Cabriolet
#1995 E320 Touring
#1985 300D Sedan
OBK #42

I'm looking at the timing mark on the Camshaft and lining it up with the matchmark on the cam tower while rotating the engine in the normal direction of rotation by turning it at the crank pully. When the Camshaft mark lines up at the cam tower, the harmonic balancer marks are 5* degress late, maybe a slight bit less.

First this not an indication of stretch, this is cam timing. There is like a 4* or more error margin the way you have measured it. Measure it with 2mm lift method. There is no need to replace the chain, bad crimps (common enough) lead to short lifespans. They make offset keys for this purpose and there is no need to crack the chain. There is no specified replacement interval in the FSM, I think they expect the chain to last all the way to the last offset key. Not that I would go that far but I believe 6* is the first offset, you are in spec but if you have the time its probably worth it.

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1995 E420 Schwarz
1995 E300 Weiss
#1987 300D Sturmmachine
#1991 300D Nearly Perfect
#1994 E320 Cabriolet
#1995 E320 Touring
#1985 300D Sedan
OBK #42

Can you explain a little more how the cam tower mark method is not an indication of chain stretch? I mean, it SEEMS like it would be a quick way to check, albeit not very accurate, but I'm still pretty new to engine timing and whatnot.

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1985 300TD-euro 352,000 mi
1974 240D (1?)52,000 mi - has a new home now

The cam tower marks are used when first installing the cam to the engine, nothing more. It was never intended to be used to measure chain stretch.
Mercedes gave a precise way to measure it. That way is 2mm valve lift on intake #1.

That said. If you had 10* of stretch and it was running fine then your IP was timed to 10* stretch. With a new chain you now have to retime your IP.

Danny

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1984 300SD Turbo Diesel 150,000 miles

OBK member #23

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The reading you got with the Camshaft Bearing Tower alignment method is a good indication you should check further and use the 2mm method to do so. This would also give you the spec you need to pick an offset key; if you want to use on.

To answer the question I think I would replace the Chain if it goes up to 6 degrees stretch as measured by the 2mm method.
If not replacing the Chain I would insert an offset key to return the Camshaft Timing to normal and re-time the IP.

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84 300D, 82 Volvo 244Gl Diesel

I've often wondered about my car, which has 128k on it, or so says the odometer. What if a prior owner disconnected the cable for 100k? I would never know. I guess the only thing I could do to sort of check, would be to do a CarFax report. Might help me locate anything suspicious, like 159k service, then the next one is at 89k, you know what I mean?

But the long and short of it is, if it has more miles on it than the odometer says, then I'm missing doing needed maintenence. The timing chain is supposed to be checked at 200k, I think.

Well, I replaced the timing chain and now it won't start. I do have the timing marks on the cam lined up and the marks on the crank at zero. Then turned the engine over by hand a few times to make sure it was all ok. Must be building good compression because it was harder with a new timing chain. The old one was stretched by more than 10*!

Funny thing though, it didn't feel very powerful before, rather sluggish in fact compared to my 300D and the fuel Injection Pump doesn't give me a shower in fuel like my 300D does. I would think even if the IP was timed wrong, it would still spray large amounts of fuel with the lines cracked. Could my IP have puked?

The marks have to be lined up at TDC on the compression stroke. Take out the #1 Glow Plug and crank the Engine by hand and see if you feel compression as you are approaching the Camshaft alignment marks. When it is aligned take a look at the Damper degree marks and see if it is at "0".

It is unlikely that the IP puked; but very likely that it needs to be timed again; after you are sure the Camshaft timing is OK.

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84 300D, 82 Volvo 244Gl Diesel