Nigel : it is over 30 years since I flew a Cherokee of any type , but from recollection some of them had an rpm range which it was important to avoid in the cruise to avoid resonance and possible crankshaft fracture - the range is only very vaguely remembered but was something like 2250 - 2350 rpm . This probably explains the 2450 rpm recommendation
I flew a PA28 in 2003 and that rpm rings a bell too.
That's brilliant chaps, many thanks and I now have a very embarrassed look about me!!
Found the bleedin' manual, for the ASI:
3. Airspeed indicator (ASI) – a true airspeed indicator is incorporated into the airspeed indicator. The true
airspeed indicator consists of a rotatable ring which is controlled with the knob below the ASI. To set the
indicator, rotate the ring until the pressure altitude is aligned with the outside air temperature (OAT). To obtain
the pressure altitude, set the barometric scale of the altimeter to 29.92 inHg / 1013.2 hPa and then read the
pressure altitude. With the ring set, the true airspeed can be read along the bottom scale.
Sounds a bit confusing to my brain or is it just my age!!
Here is the engine settings for cruising speed:
As the aircraft levels out and begins to accelerate, reduce the throttle to obtain approximately 2,400 RPM. This is
a typical cruise power setting
If only I found this little lot first it would have saved you time to enjoy much better things!!
Regards
Nigel.
I used to be an optimist but with age I am now a grumpy old pessimist.