I think you mean the primary case, I can't recall if you have a S/arm or plunger, but the other day I had to heat and do a small chicane in my early plunger pedal(the one without the adjuster lug), to clear the exhaust,used Mappgaz, and it worked all right,(needed a bit of effort) but haven't had a chance to use it yet.
Wasn't sure to quench it or not though Goldy, do you reckon it'll go brittle if done?
Cheers, duTch