Clocking a CS prop

[hudgin]

I put a Mooney engine IO360A3B6D on my RV7 instead of an Arrow engine IO360C1C like I originaly wanted. One of the differances between the two engines is the prop position on the crank. On the Mooney when the prop stops it is in the 12/6 position in the Arrow it stops in the 2/8 position. I want to know if anybody knows if reclocking it will cut down on the vibration of the engine. We fly at 23 in and 2300 RPM and the vibration is annoying. Running it at 2450 and 23 is a little better. Any reason the two manufactures clock these props differently? What about the IO360M engine?

[hgerhardt]

I have the same engine with the older non-BA Hartzell prop on my -6 and I think it's smoother than most IO-360-A's. One thing, however: before I had the engine/prop dynamically balanced, it did vibrate quite a bit between 2100 and 2600 rpm. It was only smooth above 2600. After dynamic balance, it made a huge difference in the way it felt. My engine/prop was at 0.32 ips before balance and 0.03 ips after balancing.

Mooney had Lycoming reclock the prop to make the engine smoother, at least on the Mooney airframe. Lycoming even has a service bulletin showing how to modify an -A1B6D into an -A3B6D by changing out the prop bushings.

The IO-360-M has the standard bushing locations.

I'd leave the clocking alone and get your engine/prop dynamically balanced.

Heinrich Gerhardt
RV-6, with 214 hours on the IO-360-A3B6D

[chaskuss]

Originally Posted by hudgin

I put a Mooney engine IO360A3B6D on my RV7 instead of an Arrow engine IO360C1C like I originally wanted. One of the differences between the two engines is the prop position on the crank. On the Mooney when the prop stops it is in the 12/6 position in the Arrow it stops in the 2/8 position. I want to know if anybody knows if re-clocking it will cut down on the vibration of the engine. We fly at 23 in and 2300 RPM and the vibration is annoying. Running it at 2450 and 23 is a little better. Any reason the two manufactures clock these props differently? What about the IO360M engine?

Mooney's SB M20-206-1 advises that you can change the bushings so that the prop is aligned with the connecting rod throws on the crank (3 & 6 O'Clock) to reduce vibration in the cabin. It does not reduce engine vibration, but it's transference to the cockpit. I can email a copy of this Service Bulletin off list to anyone who requests it.
The only down side is that hand propping would be more difficult.
Charlie Kuss

[hgerhardt]

Originally Posted by chaskuss

Mooney's SB M20-206-1 advises that you can change the bushings ...[snip]

That bulletin explains how to turn a -A1B6D into a -A3B6D. Hudgin already has that re-clocked configuration. He was asking whether or not he should convert to a -A1B6D, or un-clocked config.

[chaskuss]

Originally Posted by hgerhardt

That bulletin explains how to turn a -A1B6D into a -A3B6D. Hudgin already has that re-clocked configuration. He was asking whether or not he should convert to a -A1B6D, or un-clocked config.

Ah, the hazards of re-organizing one's hard drive! I suspect this is not the correct SB. However, if you read the SB, the only difference between these two engine designations is that the prop is re-clocked on the crank. I'll have to look around my hard drive some more to locate the appropriate tech article.
Charlie Kuss

[hudgin]

Sounds like there might be two SB's on the subject. I would be intrested in looking at them. PM me if you can. I think I will get the prop engine ballanced. I like results hgerhardt had. Thanks, DH

[Steve Barnes]

I was plagued with an unacceptable vibration level in the 2100 to 2450 area. At 2600 to 2700 it ran acceptably smooth. The engine is an IO540 mounted on the front an RV6. After months of trying to find a remedy, new engine mounts, timing, 2 dynamic balancings,and much more, I talked to a gentleman at hartzell. He said that they had been reclocking Mooneys,and it had eliminated much of the vibration. He told me how to do it on an IO540 and WOW what a difference. At between 2100 and 2300, where I like to run the engine, the vibration level is about 20% or less of what it was before. At 2700 the vibration was quite minimal before reclocking. Now it has increased minimally, but not a problem. Steve

[hudgin]

I was going through the posts and comments I have made and found that this forum has not been resolved. I found out that the propeller / engine combination is not certified. But the A16BD is. Converted it to the A16BD and it runs dramaticly smoother. Thanks for the input.

[chaskuss]

Originally Posted by hudgin

Sounds like there might be two SB's on the subject. I would be interested in looking at them. PM me if you can. I think I will get the prop engine balanced. I like results hgerhardt had. Thanks, DH

Heinrich correctly pointed out that I had confused SI 1098G with SI 1452. I could not find this second document on my hard drive, at the time this thread started. Aviat re-printed SI 1452 as their SB3. It can be found here.

http://www.aviataircraft.com/pix/hbulletins/hsb3.pdf

It deals with conical mount engines, not the more common Dynafocal I mounts most of us use.
Glad to hear that you fixed your problem.
Charlie Kuss

[hudgin]

Thanks Charlie for your help, I found the rest of the S.B.'s in different places on the internet. In my research I came across a comment about the props being certified to engine installations. In the TCDS I saw it wasn't certified so I called Hartzell to find out why. They didn't know but relized that the only differance between the two engines was the prop clock position. No other differances. With that info I changed it.