Anyone seen a gen3 piston failure like this?

[engineermike]

Not mine, but wondering if this failure mode is common or a fluke. This occurred on e85, ~1.9-2.0 load (Whipple, 3” pulley), 20 deg timing, no knock, 7300 rpm. Compression ring lands were not broken in the traditional way.

Sponsored

 

[Optimum Performance]

Not enough pictures to comment. This is not the cause of failure this is contingent damage.

 

[engineermike]

Here are some more, including the fracture surface.

 

[Optimum Performance]

Any cylinder wall pictures?

 

[engineermike]

Any cylinder wall pictures?

I can get some but it looked ok at a glance.

 

[Optimum Performance]

Was this an original engine or something someone built? The witness marks left by the valves are not nothing but cart horse so hard to tell.

 

[engineermike]

Was this an original engine or something someone built?…

It was an original sealed long block with about 60k miles.

 

[Optimum Performance]

It was an original sealed long block with about 60k miles.

my guess, fuel wash, connecting rod decided to maintain rpm, while piston did not. Valves may have been involved or got involved after the fact.

 

[markmurfie]

The shiny mark in the carbon patch seems like piston to valve contact. Maybe from valve float on a restricted exhaust manifold turbo application. This is a Whipple SC tho.

Fragile hypereutectic pistons cant handle a light tap. JK

Stretched a rod bolt first and this is aftermath. IDK.

 

[engineermike]

The piston was found near the top of the stroke, still held “together” by the rings and bore. I assumed the valve contact was the valves opening against the stationary piston, which pushed it down the bore a little. Cylinder head was practically undamaged.

 

[illtal]

The piston was found near the top of the stroke, still held “together” by the rings and bore. I assumed the valve contact was the valves opening against the stationary piston, which pushed it down the bore a little. Cylinder head was practically undamaged.

What kind of noise did it make or was the air just breathing out of the crankcase vent?

 

[engineermike]

What kind of noise did it make or was the air just breathing out of the crankcase vent?

Nothing noteworthy or useful. He said it sounded like he ran over gravel, which was actually engine parts bouncing around under the car.

 

[illtal]

hmmm how more robust are the gen 4 coyote blocks vs a gen 3? I suppose they (ford) won't be selling gen 3 blocks for much longer

 

[OldbutNew]

So you have a 60,000 mile engine that you decide to boost. Whether it was last week or 60,000 miles ago isn't really relevant here. We used to do this crap on 5.0 Windsors because they were cheap!! We would have 2 or 3 junk yard long blocks sitting around waiting for the inevitable swap into somebody's Fox body with the Vortech or Procharger that caused it and the stuff that went with it. I saw as many cracked blocks as piston failures.

"Cylinder wall looks ok, combustion chamber looks fine." Now there are "engine parts bouncing around under the car". So I assume that at least one rod broke? JUST the one rod? Was the wrist pin one of the parts that left the chat? Notice the pin bores are both sheared above the centerline of the pin diameter? While what's left of the pin bores looks "fine". Note the inside edge of the pin bores. See how they have a sort of radiused look? Particularly the one on the right. (Bottom picture in post #3) Same picture you can see some indication that those two halves of the piston crown were rubbing together. Which means that crack was first. Held in place, as stated above, by the rings and bore wall. But, they were moving independently. That in turn puts a bending moment on the wrist pin bores. Sometimes this will allow a pin lock to pop and the pin contact the cylinder wall, sometimes not. Did you find either of the pin locks?

Yes, these engines are boosted way, WAY beyond their design intent. And live. But these parts are designed to a cost point. Otherwise everything would get forged pistons and rods.

Based on the pictures and other information supplied, this was a piston failure due to cylinder pressure combined with RPM. I would say your root cause is a Whipple 3.0.

 

[ben1]

The engine is fine. I'm going to just put new rings in cylinder #5 and put it all back together with JB weld.

Sponsored