Tip of Spark plug disintegrated and top of the piston was badly pitted

[Okiesnake]

I was on my third session of the day, on about the third lap when I suddenly lost allot of engine power.  I limped off the track and upon inspection, the tip of the spark plug on one of the pistons (piston closest to the firewall) looked like it kind of disintegrated and looking through the hole after removing the plug you see that the top of the piston was badly pitted in the center of the piston.  I don't know what caused this.

[justfreaky]

See if this helps you: http://www.dansmc.com/spark_plugs/spark_plugs_catalog.html
Sounds like pre-ignition.

Steve

[knoxracing]

How do the other three look?

[Okiesnake]

The other 3 look healthy.  The one that was bad looked like someone smashed the end against a cinderblock.  There was no burning of the end of it, just kind of blown up.
Also - the bad spark plug was a little difficult to remove -  almost felt cross slightly threaded.
What really sucks is that I had just gotten the car back from a broken intake cam - don't know if there is any correlation between the events.

[justfreaky]

Going to guess that the cylinder was running way to lean. Check carb adjustments and perhaps richen that cylinder just a bit.

Steve

[Okiesnake]

The car is not available for me to check this right now but I was wondering if the boot around the 4th carb was not properly secured or in some way not proper, is it probable that air could have been sucked in between the carb and the intake manifold and therefore creating an excessively lean condition for that cylinder?

[knoxracing]

If you had a broken cam, it may be possible you had valve damage that was not caught causing this cylinder serious issues. Was this a 1200 or a 1250?

[Okiesnake]

What significant difference is there between the 1200 and the 1250?

[VMS Motorsports]

I think he's referring to being able to tear it down and do some checks, thus the 1200/1250 question

[Okiesnake]

1200 -  after seeing the damage, to the head,  I am sure that knowracing was correct. Thanks

[justfreaky]

Check out Gerad (Bigmil's) facebook page...
Chunks of the valve in the carb.
OUCH!

[Bigmil]

Yeah, I will be taking video and more pics when I pull the head off.  There is so much debris in the chamber I can't even tell if the piston is damaged (I'm assuming it is).

Lucky me.....