Coopers STC SA964NW
New future owner here.
Is this STC still available?
I am in the process of purchasing a 108 no dash with the O-435 that has been in it since the 50's and had a bottom end done about 400hr ago so it should be good for a bit. My plan is to save a nest egg to replace it with a O-360 STC and if I could I'd prefer the Coopers one mainly because it has a CS prop.
I'm currently in the process of using the Coopers' STC to put a Lycoming O-360 on my 108-0. I would recommend purchasing the STC as early as you are comfortable, as parts supply is pretty backed up these days with supply chain and such. It's been over 7 months since I put in my order, and I'm still waiting on the final box. I've also been told there is a 50 hour AD on the constant speed prop needed for the STC, so I chose to go with the fixed pitch instead. Give Mr. Cooper a call sometime (509-947-3168), they're nice folks and I'm sure would be happy to fill you in on the rest.
I thought the 250hr AD on the O-435's prop was bad.
I do not know what prop you considered for the O-360 conversion, but the constant speed Hartzell that is on my Mooney is also one that can be used on an O-360 conversion for the Stinson. It does not have a 50 hour AD. It has an annual AD on the hub (for cracks, an ultrasonic inspectionj) or if the hub has been replaced with the -B hub, the AD no longer applies.
If a proper Hartzell prop without the B hub is to be installed it shoujld be checked by a prop shop before installation.
I installed the Univair O-360 on my 108-0 in 2012 with fixed pitch and have been happy with it.
I currently have a Hartzell prop off a Mooney M20C that was working well when removed, but it would need the B hub to escape the annual inspection to the AD. It is for sale with the understanding that it would need the hub, though it is not cracked.
Larry Wheelock, A&P/IAStinson 108 N584LW 180 LycTexas in Winter; Indiana in Summer