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  #1  
Old 05-15-2014, 11:34 PM
drone_pilot drone_pilot is offline
 
Join Date: Jan 2014
Location: Hobbs, NM
Posts: 198
Smile Converting for Fixed Pitch

Hi All,

I have a IO-360-A1A that was out of a Mooney and configured for a constant speed prop. I am going to go with the new Catto fixed pitch prop and need to convert my engine accordingly.

Here is what I think I know so far....

1) I've got to put a 2" plug in the end of the crank at the hub
2) I've got to put a slotted/veined cover over the prop governor hole


Here is what I'm not sure of....

1) Can I remove the oil line from the front near the hub that went to the prop governor or do I need to plumb it to feed back to the case? I was wanting to put a plug in the case where the tube feeds to the front of the crank shaft and lose the tube entirely.

2) I have read old posts on this forum where people were mentioning piercing the rear plug to keep from blowing the front plug out of the crank. Problem is......where is the rear plug and how do you get to it? Is it necessary to pierce the plug with the slotted governor cover? I know there is also a cover without the slot that does not allow the oil to bypass.

Is there a reference for converting a Lycoming engine from constant speed to fixed pitch?

Much thanks, as always.
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  #2  
Old 05-16-2014, 05:07 AM
penguin penguin is offline
 
Join Date: Jan 2005
Location: England
Posts: 1,016
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Ben,

There is a Lycoming SB that covers this conversion, I don't know the number off hand.

Yes, you can remove the external pipe, it is not required to feed oil to the back of the engine - in C/S mode oil flows from the governor on the back of the engine to the prop hub. With no oil flow from the governor oil will flow into the centre of the crank and must have somewhere to go. That's what will blow the front plug that you are about to install covering your windscreen with oil.

So you have 2 options, either punch a hole in the bung at the back (before installing the front bung), or use the external pipe to feed the oil to the governor pad, and buy a special governor pad cover to let the oil back in.

Punching a hole in the rear bung is not straight forward - is a fair way back - and an error can be very costly. If you ever want to re-install a CS prop it is difficult (and potentially costly) to extract the punched bung and install a new one.

Using the external pipe to route the oil back to the governor pad is straight forward in your case - you will only need to buy the special governor pad cover. Also gives you the option to easily convert back to a CS prop in a few years time if required. In my view using the external pipe as the oil return is by far the better approach, especially with a 200hp engine.

Pete
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  #3  
Old 05-16-2014, 08:00 AM
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Mel Mel is offline
 
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Lycoming Service Instruction 1435 with supplement.

If you are going to remove the line, you must puncture or remove the rear plug.
The rear plug is at the aft end of the cavity where the front plug resides.
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  #4  
Old 05-16-2014, 08:24 AM
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RV6_flyer RV6_flyer is offline
 
Join Date: Jan 2005
Location: NC25
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Quote:
Originally Posted by Mel View Post
Lycoming Service Instruction 1435 with supplement.

If you are going to remove the line, you must puncture or remove the rear plug.
The rear plug is at the aft end of the cavity where the front plug resides.

I added a link to the Lycoming website that goes directly to SI1435.

The supplement is included in link to the Service Instruction making it one document.
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  #5  
Old 05-16-2014, 04:28 PM
drone_pilot drone_pilot is offline
 
Join Date: Jan 2014
Location: Hobbs, NM
Posts: 198
Default Good Info

Thanks everyone as usual for the very good advice!
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  #6  
Old 08-10-2017, 06:58 PM
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Kahuna Kahuna is offline
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Location: Gold Hill, NC25
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Quote:
Originally Posted by penguin View Post
Ben,

There is a Lycoming SB that covers this conversion, I don't know the number off hand.

Yes, you can remove the external pipe, it is not required to feed oil to the back of the engine - in C/S mode oil flows from the governor on the back of the engine to the prop hub. With no oil flow from the governor oil will flow into the centre of the crank and must have somewhere to go. That's what will blow the front plug that you are about to install covering your windscreen with oil.

So you have 2 options, either punch a hole in the bung at the back (before installing the front bung), or use the external pipe to feed the oil to the governor pad, and buy a special governor pad cover to let the oil back in.

Punching a hole in the rear bung is not straight forward - is a fair way back - and an error can be very costly. If you ever want to re-install a CS prop it is difficult (and potentially costly) to extract the punched bung and install a new one.

Using the external pipe to route the oil back to the governor pad is straight forward in your case - you will only need to buy the special governor pad cover. Also gives you the option to easily convert back to a CS prop in a few years time if required. In my view using the external pipe as the oil return is by far the better approach, especially with a 200hp engine.

Pete
This referrs to "buy a special governor pad cover to let the oil back in". I assume this means to leave the governor drive gear in place and just remove the governor and put a cover plate on it. Anyone know where I can find one of these? Part number? I have a system that I have to go back and forth between FP and C/S.
Thanks.
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  #7  
Old 08-10-2017, 09:13 PM
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pazmanyflyer pazmanyflyer is offline
 
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Location: Litchfield Park, AZ
Posts: 751
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Kahuna
It's Lycoming #72378 or Superior SL72378. They have a cast in (Lyco) or a thick plate with a machined recess (Superior) to allow back flow of oil to the sump.

Mahlon also describes it here:
http://www.vansairforce.com/communit...34&postcount=2

Lycoming part pictured for reference.
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Last edited by pazmanyflyer : 08-10-2017 at 09:39 PM.
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