Any thoughts on what caused this?

[TorchRed_4.0]

Only piston that looks like this is #8. Been smoking super bad and burning tons and tons of oil for months. Finally pulled the motor and doing a total rebuild starting with taking the block to a machine shop. What do you guys think caused this in the first place?

 

[nickyb]

That is what's called F.O.D.
Some object got into the cylinder that shouldn't have.
It caused damage to piston and bore.
Possibly a screw .

 

[HemiRick]

some little piece of metal got in there

 

[7991LXnSHO]

I expected to see a dropped valve seat, but this is the wrong group to see that very often. It was an Unidentified Freaky Foreign Object - a UFFO.

 

[CarMichael Angelo]

What is in the spark plug hole in the end chamber?

 

[7991LXnSHO]

Serious answer -
Is the spark plug as bad as the cylinder, and did the electrode or more cause it?

 

[v8stang289]

What is in the spark plug hole in the end chamber?

Looks like a spark plug non-fouler

 

[CarMichael Angelo]

Looks like a spark plug non-fouler

didn’t work…parts of the plug fouler fouled the cylinder.

 

[revhead347]

Looks like a spark plug non-fouler

It sure does. Probably the Dorman one in the "Help" section of the Autoparts store. Now for the real question, was it the chicken or the egg? Did someone put an anti-fouler in that hole because something had already damaged the cylinder, or did someone put an anti-fouler in there causing damage to the cylinder?

Kurt

 

[HemiRick]

The anti fowler is nothing but a spacer to move the plug out, nothing to break off. It was no doubt put in after the damage occurred.

 

[KRUISR]

The oil in the cylinder/chamber I would guess is due to oil being sucked up through PCV system. In stock set up, the hose connects to intake right at cylinder 8. If the system is pulling excessive oil vapour or oil, it will pool in the #8 runner of the intake. The engine will then suck it into the combustion chamber, fouling the plug. I had a period of time without the screen in the lower intake (below the PCV valve) and I would oil soak a plug to the point of misfire in 2 hours of driving (I was daily driving at the time).

I agree whatever is in or blocking the plug hole looks strange and there is definitely damage from something bouncing around in the combustion chamber.

 

[TorchRed_4.0]

The anti fowler is nothing but a spacer to move the plug out, nothing to break off. It was no doubt put in after the damage occurred.

I added the anti fowler because if you drove the car more than a few miles the spark plug become soaked in oil and would cause a misfire in cylinder #8. The anti fowler would make it last a few more miles but the spark plug would still get soaked in oil.

 

[TorchRed_4.0]

The oil in the cylinder/chamber I would guess is due to oil being sucked up through PCV system. In stock set up, the hose connects to intake right at cylinder 8. If the system is pulling excessive oil vapour or oil, it will pool in the #8 runner of the intake. The engine will then suck it into the combustion chamber, fouling the plug. I had a period of time without the screen in the lower intake (below the PCV valve) and I would oil soak a plug to the point of misfire in 2 hours of driving (I was daily driving at the time).

I agree whatever is in or blocking the plug hole looks strange and there is definitely damage from something bouncing around in the combustion chamber.

I added a defouler but that’s exactly what was happening, the spark plug would foul out and be soaked in oil after a few miles of driving.

 

[KRUISR]

There is a rubber grommet at the back of the intake. The PCV valve fits in. If you pull out the grommet, there should be a mesh insert below it.



This captures some of the oil vapour and lets it drip back into the lifter valley.

If you don't have one, they are pretty cheap. I got mine at rockauto.

Looking at your pic of the cylinder head, you can see some of the oil residue on the next cylinder/combustion chamber, not as bad, but its there.

 

[General karthief]

I think that thing was smoking a fair amount too.

 

[TorchRed_4.0]

There is a rubber grommet at the back of the intake. The PCV valve fits in. If you pull out the grommet, there should be a mesh insert below it.



This captures some of the oil vapour and lets it drip back into the lifter valley.

If you don't have one, they are pretty cheap. I got mine at rockauto.

Looking at your pic of the cylinder head, you can see some of the oil residue on the next cylinder/combustion chamber, not as bad, but its there.

I’ve checked that it definitely isn’t that. The smoking was so bad it was probably illegal to drive on public roads. It was burning atleadt a quart a day. Oil was just pouring into the cylinder and making the spark plug literally wet with oil.

 

[TorchRed_4.0]

I think that thing was smoking a fair amount too.

An insane amount.

 

[JD1964]

Whatever got in there and caused that damage was probably spit out the exhaust valve and could still be trapped somewhere in the exhaust system. If you ever take the exhaust off, maybe you could find it. Could be laying in the pipe somewhere or dancing around in the muffler. Theres always a slim chance it made it all the way out

 

[91TwighlightGT]

This reminds me of working on my brother's '94 Explorer. He had the 4.0L OHV V6, and he would occasionally drive back and forth from Kansas City to St. Louis to come back home from College. The Explorer always had a bit of a spark knock to it, but generally was okay if you drove it like a normal human.

He made it back from KC one day with a significant misfire. No big deal, probably just a bad plug or wire, right? Pulled the plug and the end of the electrode was long gone - the spark plug had exploded in the cylinder. Putting a new plug in didn't fix it, and a compression test revealed a whopping 40 lbs. of pressure.

So, as a relative car noob at the time and wanting to take on a big project, my parents let him borrow their Explorer and my dad and I tore the head off over my winter break from high school. When we got the head off, there was a triangular chip in the exhaust valve. Never did find the piece of spark plug, and the piston wasn't hammered, so we had the head redone and put it back together. It ran for another 7 years before it developed a rod knock and got cash for clunker'd.

Foreign objects in the combustion chamber can make a fun mess.

 

[CarMichael Angelo]

This reminds me of working on my brother's '94 Explorer. He had the 4.0L OHV V6, and he would occasionally drive back and forth from Kansas City to St. Louis to come back home from College. The Explorer always had a bit of a spark knock to it, but generally was okay if you drove it like a normal human.

He made it back from KC one day with a significant misfire. No big deal, probably just a bad plug or wire, right? Pulled the plug and the end of the electrode was long gone - the spark plug had exploded in the cylinder. Putting a new plug in didn't fix it, and a compression test revealed a whopping 40 lbs. of pressure.

So, as a relative car noob at the time and wanting to take on a big project, my parents let him borrow their Explorer and my dad and I tore the head off over my winter break from high school. When we got the head off, there was a triangular chip in the exhaust valve. Never did find the piece of spark plug, and the piston wasn't hammered, so we had the head redone and put it back together. It ran for another 7 years before it developed a rod knock and got cash for clunker'd.

Foreign objects in the combustion chamber can make a fun mess.

i think a triangular chink out of an exhaust valve is just a sign of a burnt exhaust valve, w/o any other influence.