What caused this?

[87gnturbosix]

This is a fresh rebuild with Wiesco forged pistons. Only put 5 miles on the car and maybe couple of hours run time. I put a flat tappet cam in it and the lifters were ticking, so I thought instead of hoping to get a good set of lifters I would put a roller cam in. After pulling the intake, I noticed the PS head was leaking a little coolant into the valley, so I pulled that head and this is what I found. It's on all the pistons on this side, and looks like the DS too.

I have no idea where it's coming from. Filter and screens are good, the compressor wheel is in one piece and no visible damage. I'm not sure about the intercooler. The outlet is questionable, but the inlet looks ok. Do intercoolers come apart? This is a thunder fabrication that I've had for 12 years. The TB blade looks ok to me. What could cause this kind of damage? It's a mystery to me.

 

[Mike Licht]

there is something inside the motor check the intake looks like it was moving from cylinder to cylinder and check the turbine wheel too

 

[87gnturbosix]

Pulled the dog house, intake looks good. Turbine wheel looks good. There is some scale in the housing. Could this be getting in through EGR? There seems to be too much damage for it to be scale.

 

[87gnturbosix]

This first pic is of #2 piston here is #4 and #6. 6 looks like 2 and 4 looks more like scratches.

 

[Chuck Leeper]

You glass bead the intake??

 

[87gnturbosix]

No, it still looked good. Do I need to replace the pistons? If so, I might just sell it
as is?

 

[Mike T]

Any chance of detonation in that short 5 mile run? Detonation can cause a piston to look sandblasted in a short amount of time.

 

[87gnturbosix]

Any chance of detonation in that short 5 mile run? Detonation can cause a piston to look sandblasted in a short amount of time.

It's possible. I had the boost turned WAY down but did get a few pounds for a few seconds. One thing I noticed since it's first firing. When I'd give it gas off idle, it sounded like detonation. I tried two different chips same thing. I didn't see anything out of the norm on DS. Once the rpms were up, it sounded fine. Is this what detonation looks like?

 

[20psiofevil]

If it is just the pistons that are scored my guess is cavitation since there was a known coolant leak. Was the block decked? Some pics of the cyl head bowls would help determine the cause of failure. Those hg's shit the dam bed! did the motor get hot or run hot?

 

[87boostedbuick]

Kinda looks a little like detonation to me


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[87gnturbosix]

If it is just the pistons that are scored my guess is cavitation since there was a known coolant leak. Was the block decked? Some pics of the cyl head bowls would help determine the cause of failure. Those hg's shit the dam bed! did the motor get hot or run hot?

Never ran hot and the leak was to the valley.

 

[Mike T]

Detonation damage can look very different depending on severity, duration and piston material ext. From your photos I wouldn't rule it out as the cause of the piston damage. As Mike & Chuck has suggested debris could have caused the damage as well. How do the heads look?

 

[87gnturbosix]

Detonation damage can look very different depending on severity, duration and piston material ext. From your photos I wouldn't rule it out as the cause of the piston damage. As Mike & Chuck has suggested debris could have caused the damage as well. How do the heads look?

On the machined surface of the head, there are a few spots that look the same as the piston, but not many. Couldn't get a picture to take that shows it.
I don't see this kind of damage anywhere but combustion chamber. It's hard to tell in the intake because of the cast surface, but throttle blade looks good.

 

[Pronto]

Detonation doesn't explain the intake and intercooler.

 

[87gnturbosix]

Here is a pic of the throttle blade. I thought it might be the IC, but if it was I would think the TB blade would show it.

 

[Mike T]

Even though your pistons look bad I wouldn't expect to see any damage to the cast iron heads from detonation only. Damage to the cast iron heads kind of points back to debris or maybe both if detonation was severe enough to break a sparkplug electrode or porcelain. If it was detonating that bad I think you would have heard it but it's still worth taking a close look at all of the plugs.

 

[BEATAV8]

Like mike said, foreign object damage.

 

[87gnturbosix]

Even though your pistons look bad I wouldn't expect to see any damage to the cast iron heads from detonation only. Damage to the cast iron heads kind of points back to debris or maybe both if detonation was severe enough to break a sparkplug electrode or porcelain. If it was detonating that bad I think you would have heard it but it's still worth taking a close look at all of the plugs.

All the plugs look good. How much debris would it take to do this and it didn't go past the TB. Is it possible I left something in the intake that would be able to go to all pistons? Maybe it worked it's way out. I'm lost.

 

[BEATAV8]

I've seen similar damage caused by a washer that got into a cylinder. But the spark plugs should show some sort of damage, they wouldn't be lucky enough to escape unscathed if something nasty were bouncing around in the cylinder.

The culprit(s) are probably in your exhaust pipes. The turbine wheel will tell the tale. Look closely at the leading edge of the turbine wheel blades and see if there are any chips taken out. Anything nasty in the cylinder would have to exit the engine through the turbo.

 

[earlbrown]

That shot of the piston is not detonation damage. Those nicks and gouges are from debris.