Contour Enthusiasts Group Archives Forums Modifications 3.0L Duratec turbo 3L has broken piston ring lan

Well I got the engine on the stand today and stripped it down.

At first I couldn't find anything wrong with it except the combustion chambers #2 & #4 were oily, and the plugs for those two were oily and dark while the other four cylinders were clean and white. Tops of all the pistons looked good, no signs of pitting or detonation. Heads looked perfect.

I pulled the pistons and the first thing I noticed was there was hardly any noticeable wear on the rod bearings. The rods looked good and the pistons looked good.

I began by examining piston #2 the one with the most oil in the cylinder. The top compression ring exhibited pitting in its outer edge and would have explained the blow-by. #4 also showed the same pitting. I twirled the ring on piston #2 and about 1/4 of the total ring lan fell out. It looks like a flaw in the casting of the piston. There was some parts of the fracture that were dark with soot and some parts that were freshly exposed aluminum. What I noticed first was the crack was not sharp or brittle, indicating there was a defect in the piston that finally had enough force exerted on it so it cracked the rest of the way.
The broken part would explain the little rattling noise I heard and of course the significant amount of blow-by and oil. I also found what may be a crack in the nubmer 4 piston ring lan so I will have to deal with this as well.

I'm thrilled that the rods looked great and the bearings did not exhibit any kind of stress marks or wear. Some of them looked brand new and all of them were acceptable for a block with 17K hard miles on it. The cylinders looked great except for some scuffing at the top of two of them. Could have been carbon chunks that got at the edge of the piston or maybe from the pitted upper compression rings.
I don't have any idea what caused those rings to deteriorate that way so I am opening the forum up for ideas or questions.

I don't have access to my old web page 'cause Earthlink is starting to suck. I have the pictures that I took of all these things but I can't host them anymore.

The bottom line is what to do now?
1.) Were the pistons good and the high cylinder pressures were just too much, or are the cast pistons just not good enough. Or was I the victim of a bad luck with that particular piston?
I.) Should I spring for forged pistons or buy two new ford pistons?

2.) What about the rods? They looked great. Bearings are fine. No one has blown a rod due to too much force, the failures seem to be spun rod bearings, then lots of friction and finally failure.
My gut says don't worry about the rods.

Pistons concern me and if I get forged pistons then I suppose I'll have to have the whole mass balanced again.
What does that cost?

warmonger

stock rods + forged pistons

I think rick payed close to $400 for his. he then found a cheaper place and i payed close to $275 for my 3L iirc.

if you want some info on some custom pistons, PM me.

That sucks Tom!!

Does this help in the pics department? Broken piston...

Hope it's not this bad!!
Give Buckshot a ring on those forged pistons...

What the hell was that!

It looks like an evil piston, solid black with a ring curled up in defiance.
Don't tell me you pulled it out of the river styx.

No, mine look perfectly normal. I emailed the pics to Demon though he may not know it yet.
He MIGHT host one or two for me. Definitely not caused by detonation or running lean. I really think it was just a weak piston that didn't make the grade when the stress went up. You know the old statistical variation reason where some pistons are weaker than average and some are stronger. THis one was weak.

The other pistons made the grade though so maybe I'm good.
I will consider forged pistons, but the cost and then the balancing costs...
Don't get me wrong, if I had money to blow I'd do it.
Keyser's been running 10psi without issues so far as well. Again it just makes me think it was a defective piston. If you guys could only see the broken piece, you'd see it wasn't a normal crack but apparently broke along a defective area in the alloy, possibly where there were voids in the metal.

warmonger

The Pics...













Find anything wrong with cylinder 4?

I'd recommend forged pistons myself. Then again it's not my money

This probably won't mean much but my father said he would put money down that this was cause by detonation. Sence you don't know him its not very creditable, but I also agree with anything he says

Good for you! And Him! I'm glad to see someone respects their parent.

However, I was driving the car and there was no sound of knock detonation or even pinging...AT ALL! I ran 93 octane fuel too.
Compare buckshots pistons that show detonation to mine and you'll see there is no comparison. Examine the cracked material in detail and you will see that there is an unnatural surface to a large part of it, it was not solid there. There are some small areas where there is a sharper brittle looking crack, but the rest of the area is not. This leads me to think that the casting did not cool and solidify uniformly in that area and when the ring grooves were cut it exposed a weak point. The weak point was strong enough for normal duty but not intake pressures of 7psi at 160+ degrees F.

Demon:

Forged pistons are nice, but after the above conditions and only one piston broke in a way that convinces me it wasn't detonation related but rather defective part related...I'm thinking that another stock piston that is carefully examined for defects is probably what I'll do.
And the INTERCOOLER! That will solve my problems.

warmonger

Reading the plugs by the pictures tells a lean story. The only plug that "looks" halfway normal (again, only going by my monitor settings here) is the one on the lower right. Plugs should be a light to medium brown, never white.

I think the stock pistons and rods could take the boost just fine, just tune it on a dyno. Listening for a boost muted ping is to costly of a way to tune such a beast a second time.

Tom, 2 things you need to consider on your piston replacement. #1 make sure you can use a grade #2 piston from Ford as it's the only replacement size available. Your piston should be marked and if not, you should have 6 numbers and 2 arrows on the valley of the engine right behing the power steering pump bracket that tells you the piston bore sizes. #2 You have to buy a complete piston, rod, and ring assembly as it's the only way they are available from ford and they run about $250 each! So for an additional couple hundred you could easily get the new pistons, but then you should have the engine balanced again unless they're within a few grams of the originals.

Rick