okay, so I'm new here but a slight basic mechanic, I have this ticking noise coming from the side of my engine bay right behind the A/C compressor by the engine wall just at the valve cover...its at 217,000+ miles....so here is what I've done so far.....first i was getting a Misfire at Cylinder 1, I've replace Ignition Coil, Spark Plugs (all 6), Spark Wires (all 6), Distributor Cap/Rotor, Head Cylinder Gasket, Head Bolts, Oil Sending Unit (pump), Alternator, Water Pump, Torqued everything back to factory specs, Serpentine Belt, took off and cleaned rockers and push rods, replaced Throttle Body Sensor, Valve Springs, changed the oil, cleaned and brushed out Throttle Body and ports (including Exhaust ports)....

Now the things i haven't done:
Timed the Jeep(but starts strong and no trouble idling), replaced rockers and push rods...about all i can think of right now.

What Happens when it runs:
I start it and it idle's fine, no ticking, i shift to drive then it ticks kinda loud...but when i shift to reverse, it doesn't tick....after awhile it kinda goes away when the engine warms up after a 1 to 2 hours drive.

What else can be done at this point?

 

It's a 4.0 inline six that was designed 50 or more years ago, they make noise.

 

x2 what Bustedback said. I've had a slight valvetrain tick for years.

Based on your described location, might be the evap purge solenoid.

 

Your post isn't clear whether this sound is from the engine or not.

Ticking behind the A/C canister at the firewall is indeed the evap purge solenoid. It vents vapours collected by the charcoal canister into the intake.

 

If it isn't the evap solenoid...your engine doesn't know whether you are in drive or reverse, but it does seem to matter with flexplate noise. Have you checked the flexplate bolts?