I've seen two 185's with IO550 N P or R model engines. The IO550 N,P and R are top induction, "tuned induction" 310hp. engines. I assume they were field approvals? Is there an STC available? Does it fit in an unmodified cowl? What about the engine mount? I've searched a bunch a found nothing. Anyone have any firsthand experience? Always dreaming of my next engine....

I think the Davis STC puts a IO-550 on. I thought they used a -F, but that may only be on the 206. They may use a -N on a 185.

There are STCs for the N model 550 on both the 206 and the 185. Or at least there were. You'd never get that field approved these days, and probably not in past.

MTV

I saw a 54 or 5 180 at Oshkosh about 10 yrs ago that had a top induction Continental. The cowl needed some blisters on top to make room for the induction. It was based at Cameron Park CA at the time.