First off I would never have one. I have a 2003 Rubicon with 4" lift a set MT 33 and a 4.0. My younger son has a XJ with 6" lift AT 33. However my oldest son screwed up an bought a KJ with a 3.7L V6. Well the exhaust rocker on #4 keeps falling off. The engine has 153K on it. The first time it happen he took it to a local garage and he put it back on and told him to trade it. Well it lasted a week, and he brought it to old dad. I looked at it and it was so sludged up . I tore the entire engine down had it cleaned, the heads redone with a spring pressure check. Put it back together with new lash adjusters and rockers, rings main, rod and counterbalance berarings. Well it ran a month and the damn thing fell off again. The machine shop saw nothing wrong with the springs or valves. I just figured the sludge was not allowing the adjuster to pump up right.I guess that was not it! It always happens on a startup either cold or after sitting a couple hours. Any ideas short of taking it to the crusher?  

weak spring,  or the valve is hanging up.  

springs were pressure checked by the machine shop and the heads had a valve job.  

those are the only 2 things i know of that will make a rocker pop off.  you didnt replace the springs when you had the motor rebuilt?  

Update, It was a bent valve stem, Apparently the machine shop that did the heads did not catch it which is hard to believe. I won't be using them again and will tear the heads down myself next time. I also found another one on the left side.  

No, it fell off again, now 1,2,3,and 4 exhaust have fallen off at one time or the other. New valves, springs, keeper,valve lash adjuster and cam followers. Heads were gone over by a engine machine shop. I ran the engine with the valve cover off and there is plenty of oil going to the valve train.
this really has me baffled!!!  

How is the cam?Has the engine ever ran hot?  

my guess would be rocker studs or pushrods (provided it is pushrod engine).  

The cam was checked with micrometers and has very little wear. The 3.7 has no studs or push rods. It is an OHC and the cam followers are held on by valve spring pressure only.(followers not installed yet in the photo) The hydralic valve lash adjuster are on one end of the cam follower and the spring on the other. The cam lobe pushes on a roller in the middle of the follower. I just ordered a new set of heads[ from a Chrysler dealer. List is $800 each but found a site on line that sells wholesale for $600 each. I also ordered 2 new cams at $100 each. This is one expensive engine to buy parts for. There are very few after market parts. If this don't fix it it is going to the junk Yard!!!  

The right side cam has a 2 thousands runout. The specs call for a max of 1 thousands. Unfortunatly Chrysler is out of cams and do not know when they will be available. Think that could cause the issue? The valve guides and lash adjuster bores are with in spec.  

Hello
I also have a kj 2003 model 74,000klm
the inlet rocker on the right bank next to the fire wall
has come off from just starting the car.
The dealer had it for a week, put it back on tested for 2 day gave me the car back. Cost me $420

2 weeks later i started the car rolled it out of my garage 3 meters, later that day i started the car to place it back in the garage, notice engine running on 5 cylinders, stop the car, restarted it got the same metallic noise from the head, Must be the valve hitting the piston.

I suspect the KJ V6 3.7L has a issues with sticky valves. The dealers blame poor maintenance which is not the case with mine.

They gave a an example of a guy who never changes the oil for 25,000 klm , he drove the car in fault and screwed the whole engine driving in it.

Apart from that they indicated jeep head office have not had any reports or issues with valve rockers.

Did you get any further with your kj

regards
srecko  

I prefer to err in caution. Everytime I look at specs I use this rule. If its normal runout max is one thousands runout and you have two you have double the maximum allowable. Forget the amounts and just say that phrase DOUBLE THE MAXIMUM ALLOWABLE RUNOUT. I could be wrong it is a small amount. With the over head cam engine I wouldnt push it. You could be looking for another head soon as well as followers. Followers arn't cheap as well. The engine made it to 157 thousand. It's not young anymore. I would be looking to find ways of getting more oil up to the top at around a 100,000. Don't forget to run break in additive with new valve train parts. 157000 is far from warranty. Well not now with the new "lifetime powertrain". We'll see though. Good luck  

Head has been removed they have found a bent valve.
new valve and spring to be installed
jeep Head office are supplying the Valve and spring only free of charge, as i'm the original onwer.
i need to cover the head gasket plus labour,

jeep dealer support still advise they have never had any reports of head issues on The 3.7L V6.  

just got may KJ back, Next day started it moved it out of the garage onto the driveway for a clean and wash.
4 hours later started it ,engin running on 5 cylinders again. Back to the dealer.
This time it rocker number #2 on the right hand side (opposite head), below the air filer has come off.

where does it end, another head rebuild?  

After doing research WWW.jeepengines.com.au
An Australian engine Re manufacturer, is fully aware of it and indicated all new head parts have fixed the issue, It appears only on a small amount of engines.
But its enough to keep them busy.

They even has a document from the American Re Manufacturers Engine Association,
and a part number Ref 3242661.

How ever they are unable to provide me the document.

They also advised me when it happen you need to rebuild booth heads not just the one that failed.

Has anyone been able to get any dealer or jeep engine rebuiler in the united states to admit to this fault?

Think Based on the number of engine in the us they should know something about it.

It appears there have only been about a dozen cases of this in the whole world, which is why Chrysler can keep pretending it doent exist.