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timing chain
can anyone please explain something to me?
I have a double timing chain in my 1982 380 SEC I had it checked by a Mercedes Benz mechanic and they told me I need to have my timing chain checked in about 15,000 more miles. I have a 5 degree stretch in the chain. what is a 5 degree stretch? benzat |
#2
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they told me that 10 degrees is the max
benzat |
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"Stretch" is a description of wear -- as the pins and links of the chain wear, it gets longer, and since it still has the same number of links, the angular relationship between the gears changes -- the chain path is the same but the links are further apart. This makes the cam timing late, and eventually the chain tensioner cannot keep the chain tight -- deadly in these cars, as it will "slap" and break the chain guide on the right head, get the broken part fouled in the slack, and bend the valves on the right head. Costs $5000-$7000 to fix.
The amount of stretch, measured in degrees of rotation "lag",depends upon where you measure it, cam or crank -- the cam goes half the distance of the crank per revolution, so 4 on the cam is 8 on the crank - the limit my indy mechanic uses. The double roller chain is a retofit, and vastly preferable to the original single chain (unless yours is a late version, when the factory did the change). Getting the chain replaced is vastly perferable to letting it get long enought to break! Peter
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1972 220D ?? miles 1988 300E 200,012 1987 300D Turbo killed 9/25/07, 275,000 miles 1985 Volvo 740 GLE Turobodiesel 218,000 1972 280 SE 4.5 165, 000 - It runs! |
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Peter - I'd guess it's a retrofit if it's an 1982. Somewhere in 1983 380 engines were built with a double row chain.
If the chain has play like is described, I'd change it immediately.
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2003 S500 Black/Charcoal 1990 560SEL 61k Arctic White/Grey SOLD: 1988 420SEL Black/Palomino Sold @ 85k 1987 420SEL Midnight Blue/Grey 1986 420SEL Diamond Blue/Grey 1983 380SEL Champagne/Palomino |
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