Well the cowling was designed to be able too efficiently updraught cool an igso 540. With the burden of the supercharger and the reduction gears, those cylinders must be generating about 430hp worth of waste heat.
I wonder if there are any drag or cooling compromises on the A’s with their updraught, downdraught, updraught modified cowlings? I guess the Colemill 520s would be the more critical installation.
I suppose the 500 b etc cowling leaves a little performance on the table compared to say the io540 install on an Aerostar. But it sure does a great job of cooling. My baffles and seals could use a couple days of work and a couple of hundred dollars worth of tightning up. But, the engines run so cool all the time ground, hot weather climb etc that the baffling has not gotten very far up the list of repairs needed.
More to a specific A vs B point. My fuel system recently sucked up a good chunk of the year’s maintenance budget. Although the Bendix RSA fuel injection system is slightly more pilot friendly and definitely easier for mechanics to setup in the field, the Continental continuous flow system is simpler and longer lasting and less expensive. While either system should be overhauled with the engine and should take little to no maintenance until the next overhaul, the bendix has about twice as many hoses and diaphragms that are aging whether the plane flies or not. The fuel servo is also quite expensive to overhaul.
To overhaul the servo, pump, and spider and replace all the hoses firewall forward on a B is 8-12K (per side). Probably half that for an A.