s14 ka24de #4 spark plug smashed, any ideas?

[xptnike]

Hello Zilvians, searched a bit and didn't get too much info. I found a thread about an SR having the same issue but there was no conclusive solution. Basically what happened is that I rebuilt the engine and it ran great. Have been driving it for over a month now, on and off(driving my moms car also). Drove it to work and on the way back home, it sounded like something in the engine came loose. My idle started wobbling up and down and the engine shook a bit, not anything too crazy but it was definitely not normal. After that I turned the car off. Got it towed back home to check it out. After getting the spark plugs out, I noticed that the 4th spark plug had been smashed. The Spark plug end gap was smashed by what appears to be the piston. I take a flash light and look down at the piston and there are some scratch marks on them. I took the valve cover off and there was nothing loose as far as I can see in the engine bay or from the head. As far as the rebuild goes: CP pistons, eagle rods, arp main/head studs, felpro headgasket, supertech valves, valvesprings, new seals, guides, and 248/232 cam swap(with the drilled gear on the intake side). Just the week before this happened, I did adjust the valve lash but not sure if that would affect anything. You guys have any ideas? Please let me know, I'm all ears.:-/...:confused:

[dallasb53]

maybe #4 cylinder rod wasnt torqued correctly? wrist pin coulda fucked up.

id take out all the spark plugs and turn the engine by hand and check how close each piston is at their respective TDC

[xptnike]

Okay, well...did a little more of a seach, not specifically for the ka24 but a general search. Found some more info about the problem. The possibilities are the rod bearing is out of spec enough to the point where the piston pushed up far enough to smack the plug. There could have been something that was sucked into the combustion chamber that allowed for the plug to get smashed. The other possibility is that due to bad timing or detonation, my piston ringland cracked and it was shooting around in the cylinder, eventually causing the spark plug to get smashed.

Going to be taking my head off soon to verify any further problems. Not sure what to expect yet and don't have much time to work on the car. I'll update once I get the head off.

Anyone else have ideas? knowledge?