Propeller position

[Tom McCutcheon]

I have a 160 HP O-320 in my RV-4. Can anyone tell me when the #1 cylinder is at top dead center what position the propeller should be installed? Maybe the question should have been "how do I index the propeller properly" I understand that this is important in order to have the engine run as smoothly as possible. Any help would be appreciated.
Thanks - Tom McCutcheon tommccutcheon@msn.com

[Alschief]

This is a post from Mahlon
Actually, on most two bladed props you want the blades to be at 7:00
and 1:00 o'clock with number one at TDC to facilitate hand propping.
On a four-cylinder motor this will always land the prop in the same
position regardless of which cylinder is at TDC. Almost all props are
to be mounted this way. However there are exceptions to every rule
and I have seen a couple of certified instances that mount the prop
horizontal at TDC. In those cases it was done for vibration purposes.
On a six cylinder engine, with a two bladed prop, the relationship of
the prop to TDC will change three times as you pull it through six
compression strokes. Two pull throughs will land the prop at the 1
and 7 o'clock position and then two straight up and down and two at
11 and 5 o'clock.
It normally doesn't matter which blade is the lead blade and which is
the trailing blade, unless you have an accumulation of imbalance that
would make the engine and prop smoother with one specific blade being
the lead or trailing blade. That is why some will say they got a
shake after doing prop removal for some reason and fix it by taking
it off rotating it 180 degrees and reinstalling it.
Good Luck,
Mahlon
"The opinions and information provided in this and all of my posts
are hopefully helpful to you. Please use the information provided
responsibly and at you own risk."

AL Smith
RV6 Firewall Forward
N495AB Reserved

[Rick6a]

Originally Posted by Tom McCutcheon

I have a 160 HP O-320 in my RV-4. Can anyone tell me when the #1 cylinder is at top dead center what position the propeller should be installed? Maybe the question should have been "how do I index the propeller properly" I understand that this is important in order to have the engine run as smoothly as possible. Any help would be appreciated.
Thanks - Tom McCutcheon tommccutcheon@msn.com

Would you believe mere hours ago I faced the very same problem? BUT...... it was on the O-200 reinstalled on my C-150 after doing a major engine overhaul. So consider my comments as a mere data point. The maintenance manual indicates the prop should be at 30 degrees in trail with #1 at TDC. Basically from the pilots point of view (looking forward), this means the prop appears to be in the 11:00-5:00 position.

Rick Galati RV-6A "Darla" 86 Hours
C-150 "0" since MOH

[mahlon_r]

Hi Rick,
If you are in the cockpit looking at the prop in normally goes on at 11 and 5 o'clock position at TDC from that perspective. If you are the installer/ mechanic looking at the prop, from in front of the aircraft as you would while installing the prop, then it normally goes on at 1 and 7 o'clock position at TDC, which is the same position as 11 and 5, just different o'clock?s from a different perspective.
Different times for different time zones I guess! :-)
Good Luck,
Mahlon
"The opinions and information provided in this and all of my posts
are hopefully helpful to you. Please use the information provided
responsibly and at you own risk."

[Rick6a]

Originally Posted by mahlon_r

............ which is the same position as 11 and 5, just different o'clock?s from a different perspective.
Different times for different time zones I guess! :-)

Hi Mahlon.....I suspect the guys who wrote the maintenance manual were using Greenwich Mean Time. Installing a propeller "30 degrees in trail to TDC" is in effect...Zulu time. Hmm....now is that 5 or 6 hours ahead of me????
Rick

[GyroRon]

Is there a good reason why the prop needs to be in one position over another.... other than for handstarting the engine? The reason I ask is my prop-engine combo seems to have a harmonic vibration at certain rpms and I plan to fool around with trying someone elses prop and then my own prop in different positions to see if a improvement can be made.