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How to check timing chain stretch on a V12?

2153 Views 5 Replies 3 Participants Last post by  pcmaher
I'm looking for some "easy" ways to check timing chain stretch on my 95 S600 (140,000 miles). I do not know if the timing chain was changed on the car, and have no way of finding out. I was having trouble with my beater, a 1987 Olds wagon with a 307 V8. I suspected timing chain problems. So I removed the distributor cap, and hand-turned the crank the opposite direction while watching the distributor rotor. The rotor should rotate almost immediately if the timing chain is in good shape. On the beater, it didn't. There had to be at least 20 degrees of crank rotation before the rotor began turning. Disassembly confirmed an incredibly stretched chain and worn cam sprocket. Can this method be used on the V12? Are there any other methods I can use? I'm trying to avoid as much disassembly as possible. I'd sure appreciate a good tech's advice / opinions.
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Approved MB method is by electronic diagnostic tool which detects difference between camshaft and crankshaft position. Can also be checked mechanically by removing valve covers and using two pieces of 4mm drill stock to rough check or with a dial indicator for more precision. My rough rule for the V-8 engines has been 5 degrees on the crank which I imagine would be appropriate for the V-12.

Caution: If the camshaft timing has been previously adjusted to compensate for chain wear, you will get a false (optomistic) reading.

Be safe - if the history is unknown, replace at 125K or so.
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