> I don't know about that "C85 is allowed more oomph", Greg. >
If you take a C-85 and put the O-200 crank, rods and pistons in and fly level flight with the same prop, the new engine will make EXACTLY the same horse power as before at a given rpm, ie at 2300 rpm it'll make the same hp as before and go the same speed. This is the nature of a fixed pitch prop. What you may not notice, but is true, is that if you pitch the plane up for a climb, at the same airspeed as before, you'll likely see a little higher RPM (which means more HP) and a higher vertical speed. This IS due to the HP increase attributed to the higher compression ratio. One of the requirements for obtaining the STC is that it NOT change the HP by more than 10% (+ or -) , so the engine has been proven to make no more than 85 + 8.5 = 93.5 HP. If you want to go faster, have your prop repitched to bring your new static rpm back to where it was before the modification. This will give you about the same climb capability and increase your cruise speed in proportion to the actual HP increase. Call G&N Edgecomb if you want the best price on the O-200 crank. I bought one from them a couple of years ago for $1250. I just saw an ad the other day and it's still about the same price. BTW, the 1-A/B 90 props for the C-series are not certified for the O-200, even if you cut them down. I think it has to do with the higher RPM of the O-200. John
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