Anyone seen a gen3 piston failure like this?

[robvas]

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

Basically the same aren't they?

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[Joshinator99]

Basically the same aren't they?

Negative, my understanding is the Gen 4 block shares similarities with the Predator block that would make it stronger than the Gen 3 block. Hopefully someone will chime in that has researched this more to confirm.

 

[illtal]

Basically the same aren't they?

It's a closed deck vs semi closed deck.
With a factory sleeve... A very thin one though

 

[cbrtrx]

It's a closed deck vs semi closed deck.
With a factory sleeve... A very thin one though

Gen4 has a sleeve? It's not spray bore?

 

[schmeky]

If you mean a pressed in sleeve/liner, no, I don't think so. Still using the PTWA method on the Gen 3 & 4.

 

[illtal]

If you mean a pressed in sleeve/liner, no, I don't think so. Still using the PTWA method on the Gen 3 & 4.

Hmmm let me see if I can find technical documents. I read an article to see what changes were made to the block

 

[OldbutNew]

Gen 4 is PTWA. No sleeve. Changes to the deck were mostly about coolant flow.

 

[illtal]

Gen 4 is PTWA. No sleeve. Changes to the deck were mostly about coolant flow.

Apparently, there are more oil ports, when on a mustang or a head that doesn't have cylinder deactivation there is more oil flow to the head/ valvetrain.

 

[engineermike]

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......
......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.

That all may be the case, but my question was more about "is this what you would expect?", or "is this common?", or "have we seen this before?". The Gen3 has been around for 7 years now, boosted pretty much from the start, with many making over 1000 rwhp, some running 8's and reportedly faster. If overall piston strength is the weak point, then we should see more than one fail in this way. If you follow Ford's actions, you might believe the rod is the weak point rather than the piston since the DH got upgraded rods but the same GT pistons. I've seen and heard about ring lands failing, but not the piston splitting in two., hence the question.

"Cylinder wall looks ok, combustion chamber looks fine." Now there are "engine parts bouncing around under the car".

Correct. The rod detached from the piston and attempted to saw the block in half. I believe what was bouncing around under the car was mostly block fragments.

So I assume that at least one rod broke? JUST the one rod?

I surmised that the pin pulled out of the piston, allowing the rod to do as I described above. So yes, the rod broke, but I believe that was collateral damage after it detached from the piston. And yes, only the one hole experienced the issue.

Was the wrist pin one of the parts that left the chat?

Yes, as ben1 showed, the wrist pin was found in the pan and looked undamaged.

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)

I noticed that radius as well, but it's so uniform I assumed it was manufactured that way.

 

[OldbutNew]

There is an added oil passage. It's there exclusively for the cylinder deactivation system on the F150 version. Too much oil flow will cause all kinds of valvetrain stability issues. Enough flow at low RPM will pump up the HLA's at higher RPM. The Mustang heads have oil restrictors in them for this reason.

 

[bauern]

Negative, my understanding is the Gen 4 block shares similarities with the Predator block that would make it stronger than the Gen 3 block. Hopefully someone will chime in that has researched this more to confirm.

It's a closed deck vs semi closed deck.
With a factory sleeve... A very thin one though

That's the F150 Coyote block which also uses a two part cylinder head. The Mustang Coyote block is essentially a Gen3 block.

 

[OldbutNew]

Engineermike to address your question(s) directly: I'm frankly surprised we don't see MORE of this type of failure! Ford made somewhere around, call it 30,000 S550 Coyote V8's for '23MY. (Including service) That's 240,000 pistons and rods, and. and, and... Manufacturing being what it is... a percentage of parts are going to have a hidden flaw. Something that all the quality checks missed. (Like a slight inclusion in a hypereutectic piston, maybe? )That flaw may cause a quick failure, it might last 250,000 miles. If we decide to put a few pounds of boost to it, chances that minor flaw will cause a failure go up exponentially. It's the chance we decide to take when an engine that puts 400 on the tire is asked to put 650 on the tire. Or, 1000!! The chances of failure skyrocket with every pound of boost or tenth shaved. You can do that math!!

 

[schmeky]

I agree with OldbutNew.

One small void or pocket in the pistol that occurred during the casting process is very probable.

I have dealt with castings for decades and it's not uncommon for a tiny pin hole or void to happen. This could have created a "hot pocket" so to speak and over many heat/cool cycles could have eventually caused the failure.

 

[ZXMustang]

If you had stock cats, then my guess would be cat failed and caused the failure.

 

[engineermike]

If you had stock cats, then my guess would be cat failed and caused the failure.

This was definitely not the cause.

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