Glad you fixed it.
I'm pretty sure the M110 is an interference engine, so you'd need to unbolt the cams to prevent valve contact while rotating the crank with the chain detached.
I did the chain tensioner on the M104, and I finally had success levering the cap on using a screwdriver as a pry bar and then turning with my other hand. It was still a bear and required multiple attempts.

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Prost!

Well, there is the magical 20 degree after position where the valve tension is claimed to be released. I did not scrutinize it but it is possible the valves would all be closed enough at that point to get away with moving the pistons.

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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra

How many miles did you have on yours when you performed this task? I just bought one with 164k. It runs quietly for what it is. These engines are a little coarse. But I have heard timing chain noise before on a Nissan. I imagine it is similar.

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Current stable......
17' Rogue SV 70k
11’ Saab 9-5 NG 94k
10’ e550 4matic 185k

sold
02' e320 210k
00' e430 167k
01' e320 171k (regret sale)
91' 300d 2.5t 300k (sold to ecoofidaho)
79' 240d 177k (old yellow my avatar)
87' 300d 169k (junk but fast)
85' 300tdt 261k (RBM parts delivery)
85' 300dt 68k (one owner cream puff)
82' 240d 250k
84' 300dt 198k (sold to diesel don)
91' 190e 2.3 61k
88' 260e 140k