I use to use Glyptal on my inner engine surfaces to suspend any contaminates and improve oil flow.  One place I never used it was the oil pan,  no particular reason.  I read somewhere it would retain heat in the block not sure I agree with that.  Also read Smoky Yunick used it in his ports to smoothen the flow since no porting was allowed. Of course then it got banned.  
I know folks will say it will eventually peel off but properly cleaned surfaces have yet to cause any problems.  
I would like to hear and success of failures storys   
Thanks,
Richard