12 valve piston removal
 

im working on a 97 12 valve that has low compression in 1 hole. can you pull the oil pan to remove piston with engine in truck or should i just bite the bullet and remove the engine. I have rebuilt many engines but this is my first cummins. you always learn the shortcutes after doing it the rong way first. i think the engine has melted piston because of high egts. I hope to only change 1 piston, rebuild head and assemble. not puling engine would save a lot of time and i dont plan on complete rebuild.

Id pull the engine and do new main bearings and a new gasket kit just to be safe. You maybe could pull the pan and do it but you would have to lift the engine with a cherry picker to get the engine high enough to get the pan off

Like posted you have to lift the motor a little bit to get the pan off. Yes you can pull the pistons in frame, but with you being concerned about a melted piston, there's a very good bet the cylinder wall may be affected, and you would have to pull it to have it bored.

If you are in a pinch and don't want to spend anything more than absolutely necessary then pull the head, and if the cylinder walls don't look like they will need attention then do it in frame.