Contour Enthusiasts Group Archives Forums Modifications 3.0L Duratec Piston durability

That is a front-bank piston that went?

I had two of the front-bank pistons crack in the ring area, this is a different problem. The hole piston let go, so I don't know all the data on this.
It is interesting as Buckshot had two front-bank pistons go just like mine, and one of the Streetflight engine also had the middle front-bank piston crack a ring land just like mine. All the pistons that seem to be going for whatever reason are on the front bank.
I don't know what is causing that but I'd sure like to find out. That is just too big of a coincidence for me to accept.

Tom

as soon as you find out what it is let me know.... cuz i was pissed to see this when i took the heads off. its jsut the 2.5L but still ford might be hiding something.

I'm liking this theory...

I have a 2000 2.5L non-SVT short block sitting in my basement doing nothing... i'll pull a piston off it tonite or tomorrow and take some pics... no damage on it, but it should help to prove your theory...

also I can get a hold of a micrometer if you want to post measurements of the different ring land thickness and ring thickness themselves as well as piston pin height.... i just need to know the exact points you want me to measure

Thanks! What I'm trying to find out is if the 2000 2.5L blocks also have the updated rings like the 3L's.

Procyon would probably know, but he isn't around here right now it seems.

Tom

2.5L 2000 NON-SVT Piston. Let me know what you want me to measure and I'll do that to.

Heres a pic of my 2001 3L piston....




Let me know if you would like any measurements.

Ok I just came back from my brother in-law's mold making shop

My piston has a dome center, so all measurements are not from the dome but from the top of the outer rim... we layed the piston upside down on 2 machined blocks on a flat marble work surface... pulled out some funky guage that sits flat on the table and zeroed it on top of one of the machined blocks... because he's a mold maker he measured everything 3 times to ensure accuracy...

top of first ring .158
top of second ring .368
top of oil ring .606
top of piston pin hole .769
piston pin diameter .828 (using telescoping guage)

do the math and i'm sure you can figure it all out

Ok. We have several cases of 99 3L and 2.5L SVT pistons having broken ring lands.

We have several cases of detonation.
I'm willing to say that detonation is obviously going to blow any piston, but that doesn't explain what is happening here when you just have broken ring lands.
There are 3 cases I know of where 99 and earlier engines have failed with no sign of detonation, or running lean with only cracked ring lands to show for it.
We have buckshots engine that shows clear signs of detonation from the melted edges of the pistons, and BurrtaSVT saying he has a hole in the top which also sounds like detonation.

Why do some engines show no sign of detonation and have broken secondary compression ring lands and are all 99 and earlier?
The only thing I can think of is that some of the compressive load on the top ring pushes it against its support, which also pushes against the second ring and its support respectively. However on the pistons with the thin second ring support it is just not thick enough to hold the load if cylinder pressures go really high.
Any sign of light detonation probably kills it; leaving me to concluded that the early 99 and earlier pistons for all duratechs probably have VERY little resistance to detonation and should be avoided in a FI'd or highly tuned high compression 3L engine.

Procyon, I'm probably wrong somewhere here, but you're an engine engineer so give us your take?