TPl92z

iTrader: (5)

bearings didn't let go. The car was actually driving fine and wasn't being torn down for any significant issue. The engine sounded like a lifter was on it's way out and as a precaution the heads came off to check it out... lifters were fine, but an exhaust gasket (ball gasket) was found to be loose and the sound we were hearing was likely from that. There were no audible sounds from the drivers side where this cylinder is.

This is the chamber of the cylinder that went, the other cylinders don't show any pitting of any kind. Number 5, directly in front of this cylinder, shows like it made light contact with the head as well in the same area as 7 (same coloring). All other cylinders look perfectly normal.

TPl92z

iTrader: (5)

also, air/fuel is commanded at ~11.8 and the wideband in car confirmed between 11.7-11.9 when in PE mode.

SSP Racing

iTrader: (24)

Wow, yeah maybe you are on the right track with the excessive bore theory...mic the pistons. That combo definitely has a little squeeze though. If you measured a 4.035" bore, thats a 408. If you are right and have 404 pistons in there, somebody's got some explaining to do.

=ZoomZ=

iTrader: (1)

I measured it twice and it was 4.035. I havnt measured a piston yet but i will .

All i know is as a machinist i can see .025-.030 between the piston and the wall when the piston is cocked off to one side in the hole .

I will take more pics tomorrow and post them up .

allan808

iTrader: (3)

wonder if the rings did that?, pull that piston out and checked if the top ring shattered?when i used to build them old toyota engines from the 80's ive had a few of them do that..what happens is the top ring fails and shatters into little square shaped pieces..they get up in the cylinder and make contact with piston and head before gettin blown out the exhaust..this has happend to me after i had the engine bored..

Sid447

Looks like detonation,

They also look like they are cast pistons (?)

allan808

iTrader: (3)

i dont think thats detonation..

PREDATOR-Z

Oil contamination will cause carbon buildup which in turn can create hotspots and pre-ignition. Maybe that's what seems to have happened in this case. Your motor was running rich as well.
The cause could be too much blow-by due to improper piston to wall clearances, I would get the block inspected.

=ZoomZ=

iTrader: (1)

SSP Racing

iTrader: (24)

The damaged area closer to the bottom of the relief definitely looks melted (detonation). The pistons don't "look" to have extreme clearance. Wall clearance is measured so far down from the pin, not from up top above the rings.

Is the ring broken out of the land anywhere?

JL ws-6

iTrader: (50)

Check your fuel injectors, if that cyl's injector wasn't working at all (possible) you could have gone way lean in that one hole and that in turn did cause that syl to run lean/meltdown.

I know more then one person that's happened to. Having injectors flowed/cleaned once a year is now a routine I am going to be religious about.

=ZoomZ=

iTrader: (1)

Thats not melting , its where the top crown was ripped off upwards .

What the camera picked up in that shot is the grain of the aluminum .

SSP Racing

iTrader: (24)

Yep me too.

I see what you mean but it still looks crispy in the pictures. If you took a new forged piston out of the box and broke it it wouldn't look porous like that.

I guess what I'm getting at is that the piston didn't just randomly come apart. Something happened (combustion-wise) to make the land want to lift i.e. heat, ping, overly rich mixture burning in the ring land, etc... You may never know why for sure.

I'm curious to see what tour wall clearance comes out to as well although nothing looks too whack in the pics.

It really sux we can't do individual cylinder correction with the PCM!

iOWNaWRX

Looks like the bearing got beat up on cyl 7 buddy

I know you're gonna come back strong though!

tom falco

More than likely that cylinder ran lean I have seen this many times on fords. People break a piston have the short block rebuilt then down the road same thing happens. When they lean out they ping and break apart. Seen it many times in many engines. With old time carbs it rarely happens. But with injection it can happen. Have that injector tested for flow just for your own satisfction. Sorry DUDE

O2Form

That picture clearly shows the top of the piston was hot, The top edge of the piston is melted away thats why you see all that clearance.

=ZoomZ=

iTrader: (1)

Its all your fault Trevor ! !

Time for a bigger cam .

Detonation was the problem ppl and im pretty sure it had to do with the extra material getting taken off the heads the last time they were cleaned up . I have no idea what the cc is of the head after the work was done and i should have check it before continuing with the same motor combination .

This combination worked great for a year and a half but after the head work
it looks like it needed higher octain fuel or a different cam that would bleed off compression better .

The builder is going to rework the short block and get me up and running again , the heads are at the shop now getting cc'ed and im going to most likely get a bigger duration cam .

Live and Learn i guess :/

=ZoomZ=

iTrader: (1)

Nothing was melted , what your seeing in the picture is ripped material .

A 10mp camera in s/macro mode at 3 inches can make things look really good or really bad :/

=ZoomZ=

iTrader: (1)

After taking the motor apart there IS melting around the vertical edge of the pistons 5 and 7 .

After finding out all the proper values my friend wrote me back and said .

" I keep getting 13.1:1 for compression ratio and I’ve tried like 3 different sites online.

Also, that makes the dynamic compression ratio 11.6… WAY too high for pump gas. "

lol

SOMbitch

iTrader: (8)

WHOA!! Your lucky the rest looked that good......