Hey guys, I’m new to forums so please bear with me. Im in a 1992 XJ with a 4.0, just about 163k miles. I’m asking for knowledge as I’m pretty new to motor stuff.

I was driving to work last week when I heard this light ticking sound out of my motor. Work is about 20 minutes away, mostly highway. My A/C is r12 so it doesn’t work, so I drive with windows down. It wasn’t making the sound before I got on the highway, but as soon as I got off the highway I could hear it, it sounded like ticking. It would speed up with RPMs as I gave it throttle. A couple hours later, I go back out to look at once it was cooled off, start it up and it is insanely loud knocking, as you can hopefully hear in the video lol. Needless to say I got it towed home. I pulled the valve cover off, all the rockers and push rods seemed perfectly fine. I ran the motor with the cover off and watched all of them, nothing seemed wrong with them.

So, I decided to pull the head. Everything went smooth until I saw the 6th piston was chipped pretty bad. On the top of the wall, where the chip is, there is a nice little gouge in it. This week I plan on pulling the oil pan to see what might have caused it because the under side of the head looks perfectly fine. I’m hoping someone on here can give me some insight on how I should go about this. If I pull the oil pan and there’s nothing crazy going on down there, would I be able to just replace the piston? Is the wall salvageable?





P.S. I had to cut the video down to a one second clip in order to add it to the post for some reason. But you can without a doubt hear the sound it was making.

 

I am working through a similar issue right now. I just tore mine down and it has a scored cylinder wall. If it wasn't for the cylinder wall issue I would have been looking for the why and if I could fix that I'd run it. In my case I suspect it is a moron at the shop rebuilt the engine and didn't check the piston clearances.
not that it's your issue obviously, but I'd be worried about why your piston started shedding and how that cylinder wall looks. Also how does your head and valves look? Also a cheap endoscope off eBay or wherever probably would have caught the chipped piston without a tear down. Not that it isn't needing to be tore down to fix anyway. Good luck.

 

Ouch! My bet is on a broken skirt. Supposedly a common problem on the 2000/01 4.0.
Oh, and you might be able to hone it. Piston can be removed while engine is still in the car and a new one inserted.

 

Okay so I have an update
i pulled the oil pan yesterday. Oil seemed metallicy but I didn’t see any chunks in there which I guess is good. The rod ends on all of them have a little bit axial movement, enough for me to move them and here them clunk or clink if that makes any sense. Is that kind of play normal?? In the picture you can see a small gap next to the rod end, that’s the kind of play I’m talking about.

 

ok, now remove the rod cap and pop the piston out the top for a good look.

 

okay I popped it out and got a few pictures.

 

It needs to be bored. A hone isnt going to fix the marks on the cylinder wall for sure.

 

it is down to the block. When oversizing, does that mean they oversize into the actual block? Or is the block toast as soon as it gets damaged? I’m learning here haha

 

Depending on how deep the scratches are, they can bore the block (remove material of the actual block where the piston goes) and then you just get over sized pistons to match the new bore size. No need for a new block if its not that bad and it doesnt look that bad from the pics.

Bad news - Engine is coming all the way out and getting torn all the way apart. Cant bore it with the engine in the vehicle and its just wrong to bore one cylinder. Rotating assembly will have to be rebalanced due to bigger heavier pistons. At this point, you would be doing a full rebuild.

 

Alright sweet I appreciate your responses 5-speed! I plan on pulling the block out anyway at this point and doing a rebuild. I’m thinking a 4.7 stroker rebuild, since I’ve already got it all torn apart I might as well go big or go home I gave Russ a call at Bishop-Buehl since I’ve heard so many bad things about 505 performance and he was super helpful.

 

Yup, I don't think honing it going to do it. Did you ever find out what might have been sucked in to the engine?

 

Brent, you are getting good advice from 5 speed. Take it to the bank. Don't listen to anyone who comes along and suggests shortcuts.

Now the challenge is to find a good engine rebuilder, or learn to do it yourself (not difficult) but you still need a good machine shop that will be willing to hold your hand a bit. Ask at your local NAPA - they may be able to recommend someone.

If you have a place to work on this, and can handle some down time, I encourage you to do this yourself. You will learn a TON.

 

I found a small chunk of metal on top of the piston when I pulled the head. My guess is the piston cracked some time ago and finally broke, maybe causing the jagged edges to scrape up the wall and piston skirt?? Idk that’s my best guess

Yes sir, I’m doing a lot of learning here! I’m thinking of buying a stroker kit from Russ, and I’m under the impression that the only thing I will really need to get machined is the block. Is that correct? I plan to just have a machine shop bore out the block and then assembling everything else myself, does that sound about right? Thanks for the help!!

 

Sounds reasonable. No way to know for sure. But then the question is, why did it crack? A flaw in the piston that finally let go? Or a problem with the way it was running? If there was a history of misfiring on that cylinder, that could have been the cause.

However, a complete engine rebuild should eliminate whatever problem was there before, IF you do a complete job. By that, I mean make it all new. New plugs, wires, rotor, cap, sensors.... Take this opportunity to make it ALL new.


I dunno. Never messed with the stroker world. I hope someone else can chime in here.


That's the basic idea, but.... a few more things to be considered (measured for tolerance) and done (if needed):

• Line boring the mains
• Line boring the cam
• Surfacing the deck

And then you need to consider the head. Do you want to put a marginal head on a new block? At the very least you should have it measured for twist. Yes, a big block of iron like that can get twisted. This can lead to premature head gasket failures or even a cracked head.


A good machine shop will know what needs to be done, which is why it would be good to find one that is willing to hold your hand a bit. and you'll need to be able to trust them.

Do yourself a favor - buy an engine stand. I just picked one up on Craigslist for 50 bucks. Old and ugly, but it would handle a big diesel. Worst case, buy one at Harbor Freight and sell it when you are done.



Here's how you use one (some random picture I found):

 

Stroke it! Why not? The only other thing you will need besides what Mark has said is bigger injectors. But then you open a can of worms. Maybe you should do a bigger cam? Maybe bump up the compression a little? Slight port on the head? You just need to decide if you want to go all out or keep it basic. Either way, take on the task and rebuild it yourself! I keep telling people that building an engine is simple as long as you can follow step by step instructions and do not skip on anything. You can rent most of the specialty tools from Autozone too.