Technical Engine forensics/ catastrophic failure

So guys, help me out here.
How many different scenarios can explain debris on top of the 1/2 pistons with intact cylinder walls and debris in the intake.
Debris on 5,2&8 #3 is destroyed. #1,7, 4&6 clean.
Dual plain intake and debris on right/upper plane.



Is it possible the #3 cylinder scattered debris back thru the intake valve and distributed it thru the intake and then into the other cylinders. #3 intake valve had broken pushrod and closed intake valve.

Please Give me some more ideas other than the one I’ve got.

 

Do you know where it came from? Or what it is/isn’t? Or is it all from the bad piston?

 

In my racing days, my 455 Pontiac dropped a screw out of the bottom of a Quadrajet at 5700 rpm. I modified the intake so the base screws were exposed. The screw was a standard Rochester screw just over 1" long. It went threw 5 different cylinders before busting the block in #3 hole. There were thread marks in the quench area of both heads where the screw bounced around. I found the threaded portion of the screw stuck in the piston, never found the head of the screw. It sure is possible to cross back through the intake, I have seen it what it can do!

 

That is probably what happened. I busted a piston top on one cylinder. Pieces of it ended up closing the spark plug gap on two other cylinders.
Late model engines with plastic intakes need the intake replaced after such a failure because you don't know what may be lurking in them.

 

I asked you before did this engine flatten a cam?

 

No

 

If my thinking is correct, those are the cylinders that are common to one side of your dual plane manifold. Once #3 let loose, as it would appear in your photos, debris from #3 was pulled into the other cylinders mentioned during their intake strokes through the shared passage of the intake. My guess would be that the broken pushrod might have occurred after the initial piston failure.

Now, what caused #3 to let loose in the first place is another matter.

Maybe you've already had thoughts that were similar to what I described, or feel I'm way off base. Either way, that's what it sounds and looks like to me.

Lynn

 

Lost a valve or hung one up. Busted piston and parts up the intake where a valve once was.. sleeve it. bore it. Run it.

 

yeah, stuff goes everywhere! I dropped a valve in a 454, only broke off part of a valve guide, but there was damage on the tops of every piston.

 

I’m having a hard time seeing all of that fine debris (and there’s ALOT) coming back up thru the intake. I don’t know exactly when the pushrod for #3 intake broke leaving the valve closed either.

 

Was that a intake valve ? And leaving it open?

#3 blew up, pushrod broken and valve closed.

 

yeah, it was an intake, and it was stuck open.

But under conditions like that, things work in strange and mysterious ways

 

little different angle to show the amount of debris that’s traveling thru #3 valve back thru the intake and threw the other intake valves.
4 cylinders are clean, one destroyed and three are full of shit.

 

I see the cylinder with a whole in it has no piston left. where is it? Back in the 90's my dad built a 383 Chevy with a set of Keith Black hypereutectic pistons, one broke around the skirt and the rod beat a hole in the cylinder wall and their was trash up in the lifter valley.

 

Does #5 show detonation on the bottom edge under the trash from the broken piston? Maybe show the cylinder heads. Did the valve drop or was it just bent? Debris will quickly travel between cylinders through manifold.

 

Oh yeah there’s Plenty of trash in the lifter valley.

 

I don’t see anything that looks problematic or out of sorts with combustion or timing. Valves all look good too except #8 intake has some debris holding it open.

#8

% 5


#3

 

What does the #3 intake valve look like? Any evidence of debris trapped between the valve and seat? The #3 intake is the only path for the debris to take and end up in the other three cylinders that share that intake manifold plane. With a holed piston the manifold vacuum created by those other three cylinders could well pull the debris through the #3 intake valve and back into the manifold, assisted by crankcase pressure.

 

It looks like the piston broke either in the ring lands or at the wrist pin and the rod beat it to death.
With all that destruction to the cylinder wall and piston parts in the other cylinders I'd think that there was way more damage to the head and valves but the head of the piston must have taken the beating for the head.

 

#3 valves posted a pic above

 

Did this engine have a big overbore? Cylinder wall sure looks thin but that probably has nothing to do with the initial failure.

 

.

Just 0.030 over

 

Looks like a high RPM failure of an engine built with parts that were not up to the task. But until the back story of what actually happened is told its all a guessing game.

 

I'm amazed that it didn't damage the head or at least the valves more than what the intake valve took.

Way back when I was 19 I broke a piston in a 216 in a 50 Chevy Hardtop right through the bottom ring land and the rod and sides of the piston were still going up and down in the cylinder and the head was stuck in the top of the cylinder. I wasn't smart enough then to understand that at that time I could buy a piston and rings for one piston at the parts house for about 10 bucks and go again.

 

I have seen pieces of broken pistons end up in other cylinders all the time when a piston breaks up. Usually ends up in most or all cylinders but most race engines use a single plane manifold.. with a dual plane pieces end up in the connected intake port cylinders.

 

It didn't eat a foreign object because there are no marks on the heads or valves.
This is what a small screw did to the head in my Cad 500


This is what the piston in that hole looked like.

 

It sucks when a small screw can ruin your day....

 

We had similar damage on a BBC




One of the hardened Intake valve seats dropped out. Yet It didn't even damage the valve

 

Had a carb stud nut drop in the intake unnoticed on a BBF one time. Two adjoining cylinders looked about like Mr48's pics. Sounded like every piston was hitting the head the few seconds it ran.

 

Just one word explains the debris being passed around , velocity .