I was taking a test drive to sort out the new Blue Thunder intake and 650 Holley today. About 5,000 rpm there was a loud bang and it sounded like I'd lost a lakes pipe cap. Pulled over and found the broken end of #2 spark plug hanging on the plug wire. Drove it home and finally discovered that the center of the plug had blown out and the outer part where the wrench goes was still in the head. Pulled it and got a new plug. Had to pull the header to see what was going on and don't have it totaly back together yet. Mummert heads and Champion RC12YC plug. Anyone else ever had this happen?

Defective Plug maybe?

71% of original size (was 708x19) - Click to enlarge  71% of original size (was 708x19) - Click to enlarge

I'd say so. Wondering if anyone else has had this happen.

I have seen lots of broken spark plugs.  Most of the time it was my fault.  I have never seen one blow out of a cylinder.  I'm not surprised.  Who knows where that plug was made or who made it?   


71% of original size (was 708x19) - Click to enlarge