DOHC ZC motor milled to 11.3:1 compression ratio, JG 301 cams/gears/springs (intake lobe center @108, exhaust at 109), stock pistons/rods, NOS 75 wet shot (.041 N, .023 F), Walbro 255 fuel pump. Fuel was 25% 93 octane and 75% 104 octane. BKR7E-11 spark plugs gapped to .030. Base timing retarded 2 degrees, completely stock PM7 ignition map, adjusted fuel map; AFRs were right at 12.5 in the upper RPM range without nitrous. I couldn't get a reading when I was spraying, I guess I hit the record button twice.. Compression was GREAT 2 weeks ago.

My main concern is the spark plug... I kinda think it was glowing red hot and causing the cylinder to pre-ignite.... I've heard of spark plugs doing that, but on a 75 shot? I called NOS to make sure I didn't need to get a better plug, but they said it should be fine (although I didn't tell them my CR).

Anyways, on to the pictures..









Do you think that a red hot spark plug would cause this? If so, is there much I would be able to do about it for the next time? Obviously I can't do much about it now lol.

The car pulled HARD 2nd, 3rd, and 4th gear, I let off and coasted for a bit, when I put it in 5th and started cruising, there was smoke everywhere and it started misfiring.

 

Well its apparent that the piston got really hot and expanded very quick and killed the side wall of the cylinder. kinda looks to be a lean out condition IMO. the cylinder is clean(er) then the others. and the sidewall is bad.

 

detonation like whoa

 

Could it be that the sparkplug's electrode tip all of a sudden broke off and started to bead blast the piston bouncing around inside the cylinder at the same time de-carbonizing it as well.............
The top of #3 looks eroded...

 

what injectors? cleaned/checked? possibly the injector failed or the fuel jet got clogged but that looks lean and very hot.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mr HYDE &raquo;</TD></TR><TR><TD CLASS="quote"> detonation like whoa</TD></TR></TABLE>



it got hot in there. you leaned bad and all those divots in the piston face is detonation like hyde said

 

detonation buddy,

probably caused by an improper/lean mix into that cylinder.... is that the one that the PCV feeds into?????

 

PCV is between 2 and 3.

They are stock injectors that have never been inspected/checked.

Immediately after it started smoking, I pulled over and pulled out the plugs. The rest of them actually looked rich, so I don't think its a fuel pressure issue, or the supplement fuel (from the fogger). I would like to check out that injector now, I'm curious.

Would the detonation cause the spark plug ground strap to melt off like that?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mighty137 &raquo;</TD></TR><TR><TD CLASS="quote">Could it be that the sparkplug's electrode tip all of a sudden broke off and started to bead blast the piston bouncing around inside the cylinder at the same time de-carbonizing it as well.............
The top of #3 looks eroded...</TD></TR></TABLE>

nah its called it got so hot the electrode melted off and melted the piston.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mr HYDE &raquo;</TD></TR><TR><TD CLASS="quote"> detonation like whoa</TD></TR></TABLE>
x3


Lean Condition on number #3. 75Shot..back in the day. Had to have my baby towed back 178miles...a night I cant forget





Modified by XSIintegra at 8:13 AM 9/30/2007