Open vs closed crankcase ventilation

Can anyone advise me if when converting from a closed PCV system (air in from the air cleaner/air out to the carb) to an open system (air in via breather not connected to air cleaner/air out to engine compartment) you have to make any carb tuning adjustments?
I seems to me that the air from the crankcase going into the carb could richen up the mixture so I should check the mixture afterward. Is there anything else to watch out for? I have heard about some longer term issues, but nothing was Mustang specific. BTW - I have a 1970 351W
Thanks,

Rob

I would not recommend going to opem system. Part of the reason for the pvc system is to keep blow-by gases out of the oil. Part the the oils job is to absorb some of the blow by, and filter those contaminents into the oil filter. An open system will not get rid of as many of the contaminemts and will cause the oil to break down much faster. You do not have to have the fresh air inlet come off the air cleaner, but should have a filtered air breather. Hope this helps.