It all started with a tick...
 

Last year I decided to tackle the ticking in my 2002 Montero Sport 3.0. It has about 285,000 miles so I'm not surprised it needed some work. I know these engines have a history head issues and the ticking sounded like a lifter so my first idea was to replace/rebuild the heads.

I pulled the heads to be sure nothing was catastrophic, everything looked pretty good considering the mileage. I tore the head down and reassembled it with new lifters. While I was in there I also replaced the timing belt, water pump, cam sensor, plugs/wires, and coils. I wanted to do the front main seal, but I was unable to get the pully bolt off (even with a large impact driver).

After getting it back together, I was disappointed to find the ticking was still there (although much quieter). I drove it to work for a couple days, but it felt like it would go into a 'safe mode' if I pushed it even a little. The only codes it gave were random misfires and lean fuel system.

At the end the ticking got worse and power dropped until it just quick running.

My first idea was to just replace the engine. I quickly found that the 3.0 is a hard engine to find; the only place that listed one was JEGS (from ATK, who said they aren't building those right now). They pushed the delivery date out a few months, so I thing that engine isn't going to happen. I don't have the time/space/willingness to rebuild it myself (don't even know what parts would be available) and there are no shops in the area willing to work on it.

My second idea was to pull the heads back off again to check for damage below. If not, then replace the heads. ...and on the way out replace the fuel injectors and check anything else suspicious. The problem now might be finding a new set of heads.

Should I continue looking for replacement heads, find someone to rebuild mine, or wait to see if the new engine materializes? ...or something else?
Suggestions???

You say it started with a "ticking" but didn't mention any other symptoms. I'm assuming the "safe mode" behavior was not present until [after] you replaced the group of parts.
If I got it right, it's likely you have two separate issues now. The "ticking" and a "new" one.

Were you able to isolate where the ticking was coming from originally? [ top or bottom of engine, left or right side ]

The reason I ask is the hydraulic tensioner as it begins to fail will make a "ticking" sound in the front of the engine.
My 3.5 Sport is ticking first start in the morning. I have the timing belt kit sitting in the dining room near the door to the garage.

You may want to replace any O-rings under the hood that are related to the fuel system(injector O-rings, fuel pressure regulator O-ring etc). Check for vac leaks, unless you replaced all the hoses on the plenum, they are likely to be extremely brittle by now and you may have cracked one when removing the plenum to pull the heads. That lean code makes me wonder if un-metered air is being introduced somewhere. If all else fails, re-check your timing marks and make sure the cam and crank sensors are in good shape(including the wiring). All it takes is to be off a tooth and it will run like crap and throw those codes. Ask me how I know.

There is a strong possibility the HB bolt has red loctite on it, if you need to get it off again, there a few options. (1): A really long breaker bar and a friend to add weight to the end. (2): The ole' starter bump trick. Place breaker bar against frame, bump the starter a couple times and it should pop loose(pull fuel pump relay first) (3): Blow torch that bolt, get it real hot. The crankshaft in our montys are forged steel, a little heat from a blow torch will not damage it for the short amount of time it'll take to make that loctite liquid again. (Also for the love of all things holy, clean the bolt and threads when you get it out. Re-apply red thread locker when re-assembling I learned my lesson when mine fell off last year)

On a curiosity note, how'd you get the lower timing cover off to replace the belt with the harmonic balancer still in place? I'm betting either it was already gone or you cut it off. Just genuinely curious.

How in the world did you replace the timing belt if you were not able to remove the harmonic balancer? Don't you need to remove a lower timing belt cover which is UNDER the HB pulley? Leaving HB pulley on, also prevents you from seeing the timing mark on the lower timing pulley... How did you time the engine without taking it off?

I would describe a failing timing belt tensioner noise as angry growling and crushing gravel under the hood, rather than ticking... It scared the daylights out of me when that happened. Ticking noise is more a failed or leaking hydraulic valve lifter

I totally agree. Just trying to get a little more "useful" info.

The ticking was definitely in the upper end, on the driver side. That's why my first though was a sticking hydraulic lifter, especially since if first started doing it when just after starting the engine, after a minute it would quit. But after replacing them all, I could still hear the sound a little, so it could be a valve guide... I figured with the mileage on the engine, it was just time for fresh/rebuilt heads. That's why my question was should I try to find new ones, have mine rebuilt, or just wait to see if the ATK replacement engine arrives.

I figured the fuel issue would be an easy fix. I'm not too worried about that. I will defiantly change out all of the o-rings while putting everything back together.

...getting the timing belt cover off...without removing the pulley, that was a small challenge. I ended up cutting/breaking the bottom of the cover so it could be slipped off and then back on again. It's actually not that bad. I did replace the timing belt tensioner with the timing belt, so I know it's all fine.

That explains how you got the belt off but how on earth were you even able to accurately see the timing mark on the timing sprocket and block? I know in the past I had to remove the HB because it was in the way of the timing mark. Not saying it's impossible, I just didn't fiddle with trying long enough. Not trying to sound like I don't believe you but I'm genuinely concerned that your timing is off. You really have to look at those marks dead on to get it right.

This was not the first time I changed the timing belt, it was the third time. I am confident that the timing was set correctly, but I am asking for assistance so I will check it. It may be a while before I can tear into it, it's pretty cold in my garage... I usually take a lot of pictures, so I will check them also.

Since you have experience doing this, until it's checked I'm going to assume it was done correctly. Check the plenum mounting bolts, make sure they are all tightened. Also did you re-use the plenum gasket?