Piston Skirt Damage Help!!!!

[DSG2NV03]

Hey SVTers,

This whole thing started with this thread http://www.svtperformance.com/forums/engine-tuning-214/553668-help-me-diagnose-sound.html

I had a speed shop diagnose the sounds and all the signs pointed to new heads. So.. I shelled out 2500 dollars and another 1000 to get them installed and they started it up and wouldnt you know it, it still made the same freaking sound....
So the speed shop opted to eat the labor and pull the motor apart and found number 8 piston skirt wore to all hell and number 7 starting to. What causes this? Here is what it looks like. Was changing the heads a good idea for this problem or did I just waste 2500 bucks?

piston 8

piston 7

 

[331power]

Heads wont cause that. It is probably an oiling issue, or ring issue.

 

[331power]

Maybe the bore is out of round, from an overheat, wrong size pistons or a bad piston. But being that they are 7 and 8 which are know for the heat issue, I would say maybe oil starvation or heat expansion.

 

[331power]

You basically threw out 2500 bucks!!!!!!

 

[DocB]

DSG2,

Were you runnimg a HCM?

If so, what Generation?

 

[racebronco2]

You basically threw out 2500 bucks!!!!!!

He does have an extra set of heads now. He could sell the used ones. I'm not sure why they cost 2500.00. But he did spend 3500.00 and he still has the problem. The shop should give you some kind of break to get the car running correctly. Are the walls scored? You can just replace the pistons that are bad.

 

[cobracide]

See page 13, skirt seizure on the thrust side.
Cause: Oil starvation, oil dilution by fuel or water, oil spray nozzle on connecting rod cocked or misaligned. BE bearing shell without oil hole installed.

What does the top of the piston that is damaged look like?

http://www.google.com/url?sa=t&sour...u_ybDQ&usg=AFQjCNHoNjtb5sz2yAvoX18US6cphuAd1A

 

[oldmodman]

If the shop bought the heads new from Ford you now have the latest, most desirable castings. They have nine threads in the plug holes and an improved coolant flow passage.
The piston skirt damage is very common on 03 & 04 Cobras. The cylinder to wall clearance was too tight from the factory. The factory did it that way to keep down owner complaints about cold start piston clatter. The damage usually is caused by a long run at full boost in fifth or sixth gear. The piston just gets so hot that it expands larger that the cylinder and looses it's oil film and grinds against the cylinder wall. Your shop should follow the piston mfg. specs for piston to cylinder clearance.
What brand of pistons is your shop planning to order? Don't buy stock Ford pistons as a replacement. This is a perfect time to step up to a top grade piston manufacturer. Like CP, Ross, Mahle etc.

 

[cobracide]

It looks exactly like an overheated condition now that you mention it. Good call. Do any 4th or 5th gear pulls just before you noticed the noise? Someone did. Did it happen when you were going to ship it out?

From a cooling mod page -

Cooling mod kits, Apten vs LDC Chicago

 

[DSG2NV03]

DSG2,

Were you runnimg a HCM?

If so, what Generation?

I wasnt at the time I noticed the sound, I put it on when I replaced my clutch. It is the Inviticus one that requires the tranny to be pulled. HMC2 maybe?

 

[DSG2NV03]

He does have an extra set of heads now. He could sell the used ones. I'm not sure why they cost 2500.00. But he did spend 3500.00 and he still has the problem. The shop should give you some kind of break to get the car running correctly. Are the walls scored? You can just replace the pistons that are bad.

They were 2500 dollars with new head bolts and gaskets. the walls are not scored. They are doing the labor of the tear down and replacing those pistons for free.

 

[DSG2NV03]

See page 13, skirt seizure on the thrust side.
Cause: Oil starvation, oil dilution by fuel or water, oil spray nozzle on connecting rod cocked or misaligned. BE bearing shell without oil hole installed.

What does the top of the piston that is damaged look like?

http://www.google.com/url?sa=t&sour...u_ybDQ&usg=AFQjCNHoNjtb5sz2yAvoX18US6cphuAd1A

Excellent page, thank you. Top of the piston loos fine. During the initial troubleshooting, they ran a boroscope which is why they didnt pull it apart sooner.

 

[DSG2NV03]

If the shop bought the heads new from Ford you now have the latest, most desirable castings. They have nine threads in the plug holes and an improved coolant flow passage.
The piston skirt damage is very common on 03 & 04 Cobras. The cylinder to wall clearance was too tight from the factory. The factory did it that way to keep down owner complaints about cold start piston clatter. The damage usually is caused by a long run at full boost in fifth or sixth gear. The piston just gets so hot that it expands larger that the cylinder and looses it's oil film and grinds against the cylinder wall. Your shop should follow the piston mfg. specs for piston to cylinder clearance.
What brand of pistons is your shop planning to order? Don't buy stock Ford pistons as a replacement. This is a perfect time to step up to a top grade piston manufacturer. Like CP, Ross, Mahle etc.

They are just putting in stock ford ones. I am kinda out of money on this one. :-(

It looks exactly like an overheated condition now that you mention it. Good call. Do any 4th or 5th gear pulls just before you noticed the noise? Someone did. Did it happen when you were going to ship it out?

From a cooling mod page -

Cooling mod kits, Apten vs LDC Chicago

I have NEVER done any 4th -5th gear high boost pulls, most I have done was third. Always baby this thing. Not sure what happened there. I am going to be affraid to romp on it now!!

 

[cobracide]

The car had three more unaccounted for miles on it when you got it back, right?

 

[rotor_powerd]

I have NEVER done any 4th -5th gear high boost pulls, most I have done was third. Always baby this thing. Not sure what happened there. I am going to be affraid to romp on it now!!

It doesn't take 3 miles to unload a car and load it back up. Someone decided to see if the "160 MPH" on the speedo could be reached.

 

[HISSMAN]

Definitely some skirt to wall wear contact there. The teflon has a tendency to flake of sometimes, but your has definitely been making contact with the cylinder wall.

 

[DSG2NV03]

The car had three more unaccounted for miles on it when you got it back, right?

Yea crap isnt it?

It doesn't take 3 miles to unload a car and load it back up. Someone decided to see if the "160 MPH" on the speedo could be reached.

WHo knows, I do know that i am paying for it now

Definitely some skirt to wall wear contact there. The teflon has a tendency to flake of sometimes, but your has definitely been making contact with the cylinder wall.

I wish i could upgrade all pistons but i am 5k into this project, which is a new reman motor with 1200 left over....

 

[Senkak]

I had a piston with the same problem.
Ford replaced the motor under warranty several years ago.
The tech told me the cylinder was out of round which was a manufacturers defect.
I thought it was from me driving stupidly.:shrug:


-

 

[SlowSVT]

#7 & 8 run the hottest and are likely to go first. This looks like the result of a high speed extended pull.

The factory pistons are scary close to the cylinders walls and will scuff when overheated. Sounds like they just made a call and never inspected the heads and just ordered new ones silly Rabbit. Do you have the head cooling mod? That won't solve this problem but would help.

What kind of pistons are you replacing them with and are you going to hone for more clearance? .0025 - .0035 gets my vote

Get those old heads back from the shop.

 

[DSG2NV03]

I had a piston with the same problem.
Ford replaced the motor under warranty several years ago.
The tech told me the cylinder was out of round which was a manufacturers defect.
I thought it was from me driving stupidly.:shrug:
-

Well... I hope the shop does this. I will call to make sure

#7 & 8 run the hottest and are likely to go first. This looks like the result of a high speed extended pull.

The factory pistons are scary close to the cylinders walls and will scuff when overheated. Sounds like they just made a call and never inspected the heads and just ordered new ones silly Rabbit. Do you have the head cooling mod? That won't solve this problem but would help.

What kind of pistons are you replacing them with and are you going to hone for more clearance? .0025 - .0035 gets my vote

Get those old heads back from the shop.

I have a head cooling mod now. Inviticus' HCM 2 i believe. Well they used the TSB for the head tick and it matched to the T. So that is what I did. They are replacing with factory ford. Money is a little tight now with all the cash i am shelling out so this is the route I have to go.

I will get them back, I just wonder how much I can sell them for. I am guessing they are just fine with 30k miles on them.