So, I was taking the long way home last Tuesday night after work. After about 15 minuets I got on the interstate and got up to around 75 when all of a sudden a loud knocking started.
I thought at the time that it sounded like a nut or bold fell into the combustion chamber somehow.
It sounded like a piston beating something up.
After a few seconds the sound quieted down a bit. By this time I knew the damage was already done. So, I "limped" it home.
I was finally able to pull the engine today and this is what I found...
Now, I am not missing any nuts or bolts from my ventures, or studs from my intake.
I had my air cleaners on with the rain hat covers on my 40 idf webers.
And spark plugs are damaged, but complete.
It looks like a stud or bold.
Any ideas where this could have come from?

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Definitely looks like the remnants of a stud or several... about the right size for the studs to hold your rainhats on?

I checked all studs, nuts, and bolts. All are accounted for.

Can you see if the piston is missing a chunk? That looks like aluminum to me.

Please explain how those pieces got "munched" and then spit out THE INTAKE valve....
If you had found them in the headers, then that's expected... (Have you looked in the header yet?)

You say you pulled the engine, but have you pulled the head yet?

The pieces are metal.
I used a magnet to get them out.

That's what I'm wondering too.
I didn't find anything in the header.

Man... Being ferrous and in the intake like that I can't see how it couldn't come from ABOVE the valve. Really look over all the intake parts again.

See anything I may have missed?

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Nothing looks out of place there...

I think you need to look above that. Were you running carbs or the stock FI?

Those got ingested thru the carbs. No way they were spit out of the valve.

I have 40 idf webers, with air cleaners and rain hats on top.
I would think it is impossible for something like this to get past the air cleaners.
All of the retaining bolts that hold the air cleaner and velocity stacks on are accounted for.

I would inspect the carbs and intake manifolds carefully. I'd be pretty surprised if you didn't find something missing.

Bummer....

Time for a boroscope from Home Depot...

Shanghai Tool Supply. http://www.harborfreight.com/Digital-Inspe...iNzc0NyJ9%0D%0A

I personally don't see the need for a borescope. That has to come off and the valve seats redone anyway. You'll get a good look at the piston then.

How about the screws that hold the butterfly valve in place?
Looks like too much material, but worth a shot.

Other explanation could be some piece that had been left inside somewhere and just now got knocked loose.

It's a perfectly good reason to go to the tool store and buy a new tool.

WTF is wrong with you?

I checked the butterfly screws too.

I have 3500+ miles since rebuild. Odd it waiting so long to come loose.

When did you put the rain hats on? Did it require a stud change?

I put the rain hats on when I built the engine 3500+ miles ago.
It did not require a stud change.

What the hell was I thinking? You're right. We all need an excuse to buy tools!

I guess all we have left is sabotage....

Inspect all the soft seals of the air filters for possible impressions of hardware that was caught during assembly. And eventually got loose.

Comparing them to the size of the thread stitching makes me believe this was very small
threaded part. . . Next logical thing is the best bet is it was once all one part. . doesn't malke sense
that multiple items all similar fell in the carb at the same time. . . .. . The next puzzling thing to me is that for this to make it past the throttle plates, I'd think you would have have a previous issue with the butterflys being held open and an extremely high idle. . unless the part came loose while the throttle was open, which was what you described. .
But for something to have come thru the air filters, or around them, and then to have made it up over the velocity stacks doesn't seem likely. . . I'd look more closely at the carb. .
Maybe lay all the parts out and try to reconstruct what it looked like before getting smashed, next to a ruler so we can get an idea of what it's size was. .

Here is a better picture of the pieces I found in the intake and the damage done to the head, piston, and cylinder.
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Show us the spark plug.

Can't get a Pic of that at the moment (at work) but the Spark Plug is intact aside from being beat to heck and back. I'll try to get one later this evening.

That will buff right out.

OUCH... that looked painful. I bet your heart sank.

any updates what it was ??

No, I have no idea what it was.
I've looked all over the carb for anything missing. And the engine looking for missing tin screws or anything else that looks out of place.
I did a few tests seeing if any of the tin screws or bolts would even fit down the carb. Unless the stars were just aligned perfectly, they will not. I couldn't get anything to drop through the carb.
I'm at a loss. Very very weird.

What kind of air filters were you using? If foam, it's possible that somehow a bolt was wedged in between the foam and the screen but you never saw it. Then eventually it worked its way loose. I'm sorry to see the damage, but rest assured that you're certainly not the first or last person to have it happen to them.

Done it! Sucks but I got the t-shirt.

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I have these filters with rain hats on top.

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