a little help with a xt6 distributor

[xoomer]

Hey all,

 

I just got done rebuilding my ER27, and I'm having a hell of a time getting the distributor in if I set it so that the car starts good- it pings when warm-- but when I adjust it so that its 20 btdc when warm and check mode on it doesn't want to start-- is there any tips or tricks to installing this distributor-

 

Thanks