of head. Threads on head defective. Not good even though repair was a $5 sleeve, 2 hours labor considering they almost had to replace the head. How does this happen on a 28,000 mile motor? Is this going to happen with the other 7 plugs? Oh and this is on the 2nd motor. First motor blew 2 pieces in the block at 26,000 miles. 2002 Z06. Yea I'll definitely be getting the Viper over the C6 Z06.