need opinions - engine swallowed a nut

This happened last week, haven't driven it since I heard the noise...much.

I started it up and immediately heard a knocking. I shut it down and found the jam nut on the air cleaner was missing. Yeah, my fault for not securing the nut to the rod but lesson learned. I have no idea how long it was off but like I said, started it up and heard the knocking, nothing before that.

I had to get home a few miles away, less than 5 and the noise stopped and it ran fine. I thought the engine kicked it right out the exhaust. I turn the corner and start to go up hill and there is no power and I mean none. I couldn't drive up the slightest incline. I was close enough to get my truck to tow it home.

The odd thing is, when I was idling there, I could still hear a knock but the idle would run up and down. It wasn't running good at all.

So now after getting it home I narrowed down where the nut went, the number 6 hole (rear passenger). I pulled the spark plugs and that was the one with the bent electrode. I could see some marks on the piston too so I was positive this is where it was. I was able to fish out a small piece of what I assume is the nut.

Now, this is where I need the opinions. Do I keep fishing out material or should I bite the bullet and remove the head and check everything else. If I do remove the head, is there a problem with only doing one side?

I do have the 225 V6.

What would you do? Thanks in advance.

 

Dude, you need to pull the heads. Though I'm a little surprised the valve opening is enough to allow something as large as a nut to pass through. Maybe it wedged in the valve, holding it open and the beaing of the valve against the nut is what made the metal parts.

Whatever, you need to pull the head.

 

That is what I thought I should do. You think I should pull both heads?

 

Pull the heads. I had to rebuild the engine in the surburban three years ago for a similar reason.....

 

going against the grain
just pull the one

 

I pulled all of those spark plugs and found no sign of a loose object and the engine wasn't rebuilt all that long ago so I am leaning towards doing just the one side. I will see how the first one goes. The way I am though, I will probably pull the other one too. R)

Thanks for the advice.

 

Yeah, I hear you on that. I pulled the intake the other day. Shouldn't be too much of a job, just being lazy.

 

yank the one head and inspect.
fix whatever that problem evolves into.
even if it turns into a piston and rings, just do the one hole.
no biggy
not neccesary to o'haul the whole engine.

 

What you 'Fished Out' was probably part of a ring or valve.
Something like a nut will be hammered by the 'Quench' area inside the cylinder, and will break rings in a heartbeat.

Something like a nut will often get caught under valves between valve and valve seat, and bend valves,
Or keep the valve open enough for the piston to contact the valve...

That means ruined valve seats, ruined valves, broken pistons/ring, and if you try and drive the engine,
The nut will super heat and melt through the top of the piston if it doesn't knock a hole in the piston first.

Two things you might try,

One would be to do a compression test.
If there is no compression, you have wiped out a valve/valve seat.

Second would be to roll the engine over to the TOP of compressions stroke,
And apply air pressure to the cylinder.
Listening for the air leak will tell you what happened...

Air from carb/intake means the intake valve is wiped out.
Air from the exhaust manifold means the exhaust valve is wiped out.
Air from the PCV vent means the piston is wiped out.

This is one EXPENSIVE nut!

 

Had something similar happen to my M38A1. Screw fell out of the bottom plate on the Q-Jet and into one of the cylinders (don't remember which one). The intake valve was bent and the screw was embeded in the top of the piston and the piston was cracked nearly in half.
Replaced the one piston and the intake valve and it ran fine.

RSN

 

Thanks for all the help and the horror stories. I am all set to take the head off, might have to wait until tomorrow.

 

I removed the passenger side head tonight. Didn't take too long to do. The interesting thing is I found evidence of something rattling inside the combustion chamber on all 3 of the cylinders. All of the spark plug electrodes were bent. I didn't see any damage to the valves but I did see a piece of the first piston broken off. It doesn't look like there is any damage to the cylinder wall.

I will do a more thorough look when I get the other head off, figured I might as well do that one since I am already this far. I was hoping to see the nut in there somewhere but no luck.

On goes the search.

 

I had a similar problem (nut in the intake). The nut came out was powdered metal. It had pounded up the piston and valve pretty bad. Oh and it damaged the cylinder wall some. So since the engine had 250k on it... ...it got a complete rebuild including being bored out to take care of the cylinder wall problem...

 

Unless it embeds in the piston, you normally don't find it.
Goes out the exhaust valve and causes minor restrictions there.