hole in number 1 piston

something broke in my motor when i was on the freeway yesterday. limped it home, just a few more miles. had it towed to the shop this morning to get it figured out so could bring it back here to fix it. i thought it might be a blown head gasket or broke rocker. compression test showed no compression in the first cylinder. you can see a hole through the piston when you look through the spark hole.

what would cause this?

'95 w/ '96 4.0 motor. K&N kit. throttle body spacer. performance distributors firepower kit. flowmaster. no cat.

running too lean is a possiblity. How many miles on the engine?

its got about 100,000.

what would cause it to run lean. i replaced the fuel filter and have run fuel injector cleaner within the past 5,000 miles. is the computer not compensating for the increased air-flow from the mods ive done?

guess it would be easier to swap in a new motor than rebuild the motor huh?

i really doubt that it was running too lean. I just know thats a possible cause of burning a hole in a piston in cars we've messed with with turbo's and nitrous. If anything, maybe your number 1 fuel injector isn't working properly. 100,000 miles is relatively young for a 4.0 so that probably isn't from old age. You will discover more about the cause when you tear into the motor and see the condition of other components.

yeah, i guess ill just have to wait and see. i need to find a new ride in the mean time. anybody got an extra XJ they need to let go in the tampa bay area?

im gonna rebuild this motor but need to find either another XJ or another motor to get me back on the road. no time to rebuild it now.