Suggest a leak down test before disassembly to identify any problems such as rings. Valve seals, definitely replace if disassembling the head. Use new bolts or measure the old as per factory specs. Replace the timing chain.

Read up on how the chain tensioner gets disassembled and reset unless you already understand how it works.

Use an inch pound torque wench on the rocker arm to head bolts, the threads in the head pull out easily.

Good luck!!!

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer