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check out the hole in my piston

Never seen that happen before. Of course, I've never seen a piston completely disappear either (in my friend's 97 with 97k on the clock)

Cylinder2.jpg
 
the hole in the piston is called pre-detonation. it happens when air leaks in and leans out the mixture causing early detonation and holing in the piston. ive had it happen on my 2-stroke dirt bikes but ive never seen it on a car engine
 
i could see where the gasket was leaking. for a while it was running rough for a few minutes after a cold start. once the four-oh warmed up it would be fine.

i think the fact that i was running the fire power ignition kit with plugs gapped to .065 didnt help any. i was running stock injectors.

i thought i had a vacuum leak some where but i couldnt find the problem until it was too late.
 
Blaine B. said:
Never seen that happen before. Of course, I've never seen a piston completely disappear either (in my friend's 97 with 97k on the clock)

Cylinder2.jpg

how in the hell did that happen?
 
Blaine B. said:
Never seen that happen before. Of course, I've never seen a piston completely disappear either (in my friend's 97 with 97k on the clock)

Cylinder2.jpg

had a 4banger in here recently that threw me a curveball like that. LOL same reaction......."where the hell is the piston".

after finding the pieces of the piston in the oil pan and blown out of the side of the block, i noticed that the piston had started to wobble on the pin causing the bottom of it to crack, and then (here's were i can only assume) allowing it to shatter and fall straight through and start getting chewed up.

sure made for a good laugh though.
 
Its a 4.0. If you fix right, with a bright shiney new piston it'll run like crap, now on the other hand if you were to slap some JB Weld on it, shove it back in there it'll probably run like a champ.....lol
 
dizzymac said:
Its a 4.0. If you fix right, with a bright shiney new piston it'll run like crap, now on the other hand if you were to slap some JB Weld on it, shove it back in there it'll probably run like a champ.....lol
lol, yeah JB weld was exactly what i was thinking. i was hoping i might be able to get away with using a piston from another 4.0 block i have. i would use new rings of course.

actually, i compiled a parts list to fix this. maybe you guys can let me know if i left something out or if anything is unnecessary.

1. piston(i wanna use a piston from my '95 block. this one is a '96)
2. piston rings
3. rod bearings(in case some peices of the piston got in there)
4. new head bolts (i already used this set twice)
5. head gasket
6. intake/exhaust gasket(i obviously have the intake/exhaust off. can i use the gasket more than once?)
7. oil pan gasket(same issue as intake/exhaust gasket. can i use this more than once?)

anything else?
 
Maybe a timing chain cover gasket?

I dunno, my friend's Jeep was ticking for awhile, then he said he suddenly lost power on the highway. Then started it back up and babied it off of the highway to a gas station for a tow.

We did find have of a ring when st stuck a magnet down the cylinder :)
 
Since you're replacing all of the other gaskets, why not?

Maybe do the rear + front mains while you're at it as well since the pan will be down.

Then you'd have a leak free motor for sure.
 
tigerShark said:
7. oil pan gasket(same issue as intake/exhaust gasket. can i use this more than once?)
I put a one piece pan gasket on the Jeep about a year ago, and I just reused it on my rebuilt engine (I had to swap over the old pan). I had heard of others reusing them so I figured I'd give it a try. No leaks after 400+ miles so far...
 
scca28 said:
I put a one piece pan gasket on the Jeep about a year ago, and I just reused it on my rebuilt engine (I had to swap over the old pan). I had heard of others reusing them so I figured I'd give it a try. No leaks after 400+ miles so far...

the gasket seemed to be in good shape. maybe ill give it a try reusing it. thanks for the positive reenforcement. it is a one piece btw.
 
scorpio_vette said:
BUT..........there is. i don't know if i would risk it. if there is any kind of sidewall damage, it might/will be enough to make you loose compression.......
im not saying that there isnt any sidewall damage. im just saying that for that amount of damage to the piston, i would expect to see more damage to the sidewall in the picture.

so much for advice on my issue. now were talking semantics about this picture that isnt directly related to my problem. im not trying to be selfish here. i was just looking for some pointers.
 
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