06 4.0 Rebuild Advice (Noob but have read a lot)

[Trouble]

Hi everyone, looking for some advice here on what to do during a rebuild/motor freshen job. I have a 4.0L with 84k on the clock that I feel is going to give up the ghost soon. On startup I get a horrific clacking noise until it warms it, it’s definitely not a tick, but more of a CLACK CLACK CLACK, which leads me to think bearing failure. I put the Jeep on its side last April but quickly cut the motor after only a few seconds. The noise used to go away at idle, but now it is there ever so softly and is gradually getting worse over time.

I also have an exhaust flutter. Kind of feels like a miss from inside the vehicle but no codes, I can see the RPM drop 50-75 and the timing advance 2-3 degrees for a split second watching my scan tool. Headlights and interior lights also dim a little.

Here is a video of the exhaust noise:

https://www.youtube.com/watch?v=eLB5IvtjCfo

Despite all of this it runs fine, drives fine, and doesn’t feel like there is power loss. I’m just thinking its time to get moving on heading off complete failure when spring gets here.

I’ve looked into stroker, talked to a close friend who had one, and also talked to the owner of a machine shop who is friends with my buddy and did his stroker. My friend has known the owner for a long time and I feel good about pulling the engine and letting him do the work.

I talked to him about the stroker thing, and his advice was to just go .030 over, freshen the block with new bearings, and to just leave it stock minus the bore. His reasoning being you’re sacrificing reliability and such for a stroker, and if I’m looking for power just go with a supercharger kit.

I took a look at this “recipe” and tried to hunt down and price what I’ll need…

My current engine is a 4.0L in an 06 LJ.

Jeep 4.2L 3.895" stroke crank $200 (Won’t have a core to return)
Jeep 4.0L 6.125" rods (My factory rods are this spec, I think)
Keith Black UEM-IC944-030 pistons $565
9.6:1 CR
CompCams 68-231-4 206/214 degree camshaft $136
Ported HO 1.91"/1.50" cylinder head (Valve specs for my current head match this if my research is right)
Mill block deck 0.020"
Mopar/Victor 0.043" head gasket
0.050" quench height
Ford 24lb/hr injectors with adjustable FPR or MAP adjuster for '87-'95 engines, Ford 24lb/hr injectors for '96-'04 engines, '99-'00 Chevy LS1 26.2lb/hr injectors for '05-'06 engines
264hp @ 4900rpm, 324lbft @ 3500rpm

So I’m looking at:
Pistons – 565
Cam – 136
Crank – 200
Lifters – 65
Gaskets - ??? (Haven’t looked into a main gasket set price)

What else am I missing? My 4.0L has that funky OPDA assembly. Do I need to also get new valve springs and rockers? Do I need a different than factory timing set? I’ve been trying to learn as much as I can on my own but I am feeling a little frustrated.

I would like to hear anyones opinions on if I should go for the stroker, or just refresh the motor with a .030 over. I really don’t want to pull my engine and do this all over again for a long time. Having a 4.0 with issues like this at 84k is already frustrating enough…


The way I see it:

Pros –
Buying new pistons anyways
Will be buying new cam/lifters anyways
Will probably do the timing set anyways
Engine will be apart for the rebuild anyways
Extra cost of parts not that much greater than I what was going to buy anyways
DA POWAH

Cons –
Reliability
Drivability
Cost of extra machine work
Cost of supporting mods like injectors, TB Bore, etc

[ruffy01]

The noise you're describing, does it go away under acceleration?
It may be the timing chain if it does.
A failing big end or main bearing shouldn't affect your idle or RPM & a loose timing chain will make a "clack, clack" noise.
Alot cheaper than a rebuild if that's the problem.

[FlyinRyan]

Email me if you want to tune your new setup for some real power....I have several known good calibrations for various strokers.

[Trouble]

The noise does not go away under acceleration, but only once the engine gets warm. It used to go away completely but now its still faintly there at idle. I have a couple of different funny noise issues going on. This morning I had a loud sharp ticking, almost like an exhaust leak but it didn't taper off like one, it just abruptly stopped, so probably lifters or other in the top end. It seemed to be coming from the valve cover.

This whole engine trouble is really unfortunate, I have not abused this motor other than putting the Jeep on its side for a few seconds. It's always had close to 3k mile oil changes with high quality oil and a Purolator or Mopar filter...

[clarkkent]

Trouble
I'm in the same boat. 04 LJ 80k clacking main bearing. So I am also going the stroker route. I just started looking into them and want to get started before mine gives up the ghost.

[Retlaw01XJ]

My '01 had a loud knock. Sounded like a rod knock (bad bearing), but I was a little perplexed as it still had great oil pressure. Turned out it had a broken piston skirt on #2. It's a somewhat common problem. I bought mine this way, so I can't say if there were any early warning signs.... I don't know if there was mild piston slap that eventually resulted in a broken piston, or if the piston just broke.
Only way to check for a broken piston is to drop the pan and take a look.

If you suspect a bad bearing, the oil will have a metalflake or metallic sheen to it due to the bearing particles.

Another cause of a knocking noise is a cracked flexplate or loose converter bolts.

The comp cam will require valve springs and retainers that can take the extra lift. It also uses the early timing chain set that uses a cam bolt/pin arrangement to keep the cam moving forward/backward. The later engines had a more desirable cam retaining plate.... tough to find non-stock cams that work with the plate.

Forged KB pistons can be found on eBay for a much better price, oldyeller204 (Titan) has them for $325.
http://www.ebay.com/itm/Jeep-Stroker-Fo ... cc&vxp=mtr

[Jim K in PA]

Trouble - have you addressed the OPDA issue yet? At 84k it may be time to deal with it if you have not. Mine did not make the ticking noise, but it did exhibit the "laughing monkey" symptom. Look into it, and do not regard the VIN cutoff numbers relative to the recall as gospel. Just about any of the later ('05-'06) OPDA/CPS units are likely to be suffering from lack of proper lubrication to the upper shaft section. Fix is relatively easy, and worth checking before you throw $$ at the engine. Lifter noise is obviously a separate issue.