Does anyone know when using an inch pound torque wrench with a 6" extention, if it changes the torque value? if so by which way and how much ? Thanks

 

No. The only way you would change the torque value is if you were to extend it beyond the pivot point with say, a bar with the square drive on one end and a square hole to accept the drive on the torque wrench. Extensions which go straight on to the drive do not move the pivot point so they do not change the measured torque value.