It's got 155k miles. Some bad piston slap when warming up but otherwise seems to be running fine.

Seemed to get worse after I had the oil changed recently.

Any thoughts?

It'll run for decades the jeep 4.0 is not known as a quiet engine.

What oil did you put in it? If it wasn't 15-40 rotella it needs to be.

Get rid of the Fram or Fram made filter too and most of your noise will go away

you could put heavier oil in it like 2nd poster said. i wouldnt worry about it though.

Keep driving it.

After the OP replaces the "quick lube" filter with a quality one (wix mopar ect)

I6 engines especially the 4.0 and ford 300 are extremely sensitive to shitty oil filters. The OP comment of "after an oil change" is a red flag for this

how does an oil filter cause/stop/affect piston slap?

My 98 Cherokee has 200k on it I usually change oil well past the service limit (say 6000 miles) and change the filter. It's a noisy engine, but seems to be built like a tank.
I wouldn't worry too much about the noise.

People think every noise an engine makes is piston slap these days.

Riddle me this. How does a fresh oil change cause it to start?

different weight oil may hide the sound some.  old dino oil is thicker than new dino oil of the same weight.  

I still don't see how changing a filter would do anything though

Well for starters you don't end up repriming the entire oiling system each time the engine sits for a few minutes.  A functioning anti drain back valve in the filter is critical for these and other engines where the filter isn't mounted top skyward. Something you simply don't have in a Fram or made by Fram oil change joint filters

I've been here and done this. These engines like no other will teach a person the importance of a quality (read not orange) oil filter

What's the arfcom of the jeep world?

Jeepforums.

They'll tell you the same thing I did

Not at all questioning you guys. I was just wondering if jeepforums was better than the other 4x4 places. Like m4carbine.net is a pale imitation of arfcom :)

ETA: I happen to have 10gal of rotellaT for my truck that I'll put some into my jeep next oil change.

I am pretty happy at wranglerforum.com lots of traffic and lots of help, links and stickies. Not a lot of trolling.... jeepforum is ok but I am not a member there.

Pirate4x4

Ask all of your questions in Hardcore Tech. Really smart and friendly guys over there.

and make your username Charlie Wenzel

Been running synthetic with ZDDP for most of its life in my 1993 XJ 4.0.

No leaks, no issues. Don't even have piston slap and its pushing 300K.

I think the only thing I've ever replaced on it was starters and the instrument cluster.

Been a hell of a rig.

4 engines that just don't know when to die…

AMC 4.0
Cummins 5.9 (unless its a common rail with the factory injectors around 150k miles)
Ford 4.9
Vortec 4.2

Just let it run. My XJ is pretty close to yours in milage. Keep driving it until it refuses to run. Then you rebuild and stroke it to a 4.2.

My '95 Cherokee with that same 4.0l engine had 230,000 miles and still going strong, other than a rear main seal leak. I sold it for a Wrangler. 2000, 120k now.

Has anyone ever seen one of these engines die?

Amc 4.2 (258) even carbed are pretty good runners. Even as a carbed motor they can last a LOOOOOOOOONG time.

If you stroke a 4.0 with the 258 crank, its typically a 4.6L.

Yes

INTERESTING

http://www.rockcrawler.com/techreports/stroker40/index.asp

do tell.....

If your lucky you'll get 20,000 miles out of one before it's puking oil out all over the place from blow by caused by excessive cylinder wear resulting from the really bad rod angles involved

Does .25" of extra stroke really matter that much? Wouldn't the original 258 have had the same problem?

Exactly. People with no knowledge on the subject, especially about vehicles, should just not post. Wrong information is worse than no information.

OP, as mentioned, they're noisy motors. But beasts nonetheless. Oil won't help piston slap, if it truly is piston slap. Thicker oil will help with rod knock and noise lifters. If you noticed something different after you changed your oil then that should tell you right there.
I suggest the Rotella and grabbing a quality filter like Wix.

I'm not sure there's many internal combustion motors on the planet that can suck a few quarts of water through the intake and survive.

When you're sitting in a mudhole and watch an oil slick float by your door... Yeah the motor is FUBAR no matter how tough.

Well, did you try it afterward ?

yeah, i'd call that dead.

Here's what I found:

There are two roads to building the 4.0L stroker. The budget method uses a 258 crank, 258 rods (5.875-inch long), and pistons with the stock 4.0L piston pin height (around 1.60 inches.). This is called the "short-rod" engine. The more expensive "long-rod" method uses the 258 crank, the longer 4.0L rods (6.125-inch) and a shorter piston pin height dimension (slightly variable but around 1.38 inches).

While the differences in a long- and short-rod motor can be huge in a high-revving', mega-power V-8 engine, the performance differences between the long- and short-rod Jeep engines is small. That's partly the inherent design limitations of an inline-six with a long stroke, and partly the way the engines will be used. The long-rod Jeep strokers offer a somewhat broader rpm range and, in theory, the short-rod setup is subject to more wear. Frankly, we doubt the wear differences will amount to much for most of you. The rod ratio (the ratio of rod length and stroke length) of the short-rod engine is identical to the stock 258, and they were known for a long life. Because we wanted to make this an "every man's" budget stroker, offering mainly a big boost in torque in the ranges where most 'wheelers work, we stuck with the short-rod option and off-the shelf parts.



From: http://www.fourwheeler.com/how-to/engine/129-0711-1987-2006-jeep-40l-inline-six/#ixzz38tOAkrzX

Sounds like the Titan 4.6L kit, most homebrew strokers last as long as a regular 4.0 block. Titan and Golan's stroker kits have been known for shit build quality and general high failure rates. Most stroker folks know this.

Friend of mine has been running a 4.6L that he threw together in 1995 as his daily driver for awhile now. I think he runs roller rockers and a HV oil pump and a 258 4 barrel carb intake, but the rest is pretty much stock.