My diesel head seems to fit my Norvel Big Mig .049 engine OK. I won't know for sure until I actually run the engine with the head on it though.
The diesel head seats a little lower than the glow head does, as the glow plug insert causes the glow head to seat a little higher.
I had to be patient and carefully move the head around the cylinder until the threads mated Ok and then screw it on down.The threads seem to be fairly tight in matching up to the cylinder, you have to get it just right before it screws on OK.





diesel head compared to glow head with insert


diesel head compared to glow head without insert


diesel head compared to glow head without insert


diesel head compared to glow head with insert