Oil cooler radiator is fine at standard size, recommend unbolting it from the casing (vibration can crack the bracket) and mount it on fabric reinforced rubber strip hanging out to the side, the stock case has leak holes to blow fan air through the radiator but I blocked those to give max air to cool the heads and swung the cooler out to one side to catch airflow.Factory Briggs 627s are rated up to 23hp. They have some cooling capacity in reserve to cope with filthy fins and general abuse. I don't know how much, yet. I am planning to use one, and would like to get north of 30hp. I am half expecting to need to add internal oil cooling to achieve my target. Yes, a bigger oil cooler, too.