Im putting a bung in my downpipe for my o2 sensor only thing is its difficult to drill and weld with the downpipe on the car and i cant be assed to take it off. Do you reckon JB weld will hold it? At least for a few short runs so i can get the A/F ratio's right then take the turbo kit apart so it can be tidied up etc etc. Myu basic question is will the down pipe be too hot...
thanks in advance

 

It will fall of in a heartbeat. Even if it stays off it will be outgassing and throwing off your reading. Weld it on.

 

JB Weld can't tolerate heat so I'd be surprised if it even lasted 30 seconds.