Static Rpm at run-up

first thing to check is to make sure your tach is accurate. I checked mine and found it was 200 RPM off.

Matt
on the RPM question . . . .
I have a 1946 415-C with C-85
Static RPM is about 2150
Takeoff max about 2300 but
Engine has placard showing 2575 max rpm
I have McCauley 7150 prop 4 years old
in level flight with mixture properly leaned I get 2450 RPM full throttle
fuel flow just under 5.5 gal per hour
Cylinder head temps all around 300 +
seems like I should not have to go full throttle to get 2450
What do you think

Bill

With a fixed pitch prop you will not see max RPM until the plane is in the air, until then the engine is working hard to pull the plane. think of it as trying to start your car from a stop in 4th gear.

Greetings all,

I’m embarrassed to admit I’ve never noticed this before or I have flying turbine Helos and have forgotten.

My static RPM run up number is 2100 according to the Forney POH.  I operate almost exclusively from a short grass strip and noticed my full power rpm is about 2250-2300 on my take off roll which increases to about 2450 on climb out above 500 feet agl.  

What are the bare bones physics behind the power plant not producing max rpm during take off roll. 
thanks