Classic/Antique Car Repair: air cleaner, 1968 plymouth valiant, 225 slant six

Question
i have a 1968 plymouth valiant with the 225 slant six. it has the original air intake drawing its air from the valve cover.  im thinking of up grading it to an open air filter so it can breath better, is this recomended for a engine thats stock.

Answer
That line that runs to the valve cover from the air filter is part of the emissions system. When the engine is running under light load it feeds filtered air from the air filter to the crankcase. When the engine is under heavy load the blow by the piston rings then is forced into the air filter venting the crankcase. Removing this upsets the crankcase breathing. I am not a fan of the open air cleaners but rather make sure that the factory systems that also cleans the air to the crankcase is in proper working order.
Brad