2575 is the red line and rated HP RPM for the 85. 2400 is a pretty conservative cruise RPM so crank it up.
Kevin --- In [email protected], "Ed Burkhead" <[EMAIL PROTECTED]> wrote: > > > Frank, > > John Cooper said it beautifully. > > I'm inclined to agree with him on all his points. > > Check your prop stamp and see if you have the prop's history. Call some > prop shops recommended by these guys and your FBO/A&P/AI and get estimates. > The prices he mentioned match my memory from casually watching the > reconditioning/repitching correspondence. Or, maybe, the price might have > risen to what Bill said. You can find out tomorrow. > > The only downside to repitching to flatter is that it cuts down on your > cruise speed at a given rpm. With my prop repitched to 7146, my climb was > increased to tolerable and my Coupe's airspeed at 2400 rpm was almost > exactly 100 mph. > > Being a timid and insecure type (as anyone can tell you), I continued to > cruise at 2400 rpm (except for just a very few instances). > > Mind you, with a flat pitched prop, 2400 rpm isn't working the engine very > hard at 100 mph. Several people including mechanics told me to go ahead and > "let it spin" and run at higher rpms. > > Engine experts! > * Is it bad to run the C-85 engine at more than 2400 rpm in cruise when you > have a flat, climb prop? > * If the plane cruises at 108 mph with the 7150 prop, is it OK to turn high > rpm to cruise the same airspeed? > * Would that cause lower or higher stress on the engine than flying 108 mph > with the 7140 prop? > > Inquiring minds want to know! > > Ed Burkhead > http://edburkhead.com East Peoria, Illinois > ed -at- edburkhead???.com (change -at- to @ and remove "???") >
