Removing Doyn conversion

[idoflilo]

What would be involved with removing a Doyn 0-340 A1A conversion and converting back to original cont.engine instillation? I am a new member,and any information or personal input on this subject would be greatly appreciated.

[c170b53]

Welcome to the association, glad you joined up and ask away we are here to help if we can. Good luck with the machine, you"ll get it sorted out. Really what you want to do is find the replacement engine which will determine what you need. It would be easier to replace with another Lycoming but either way there's a few things you will need. You need an engine, prop, appropriate spinner depending on model,engine mount ,exhaust ,carb box ,cowl bowls with specific engine baffling, engine controls and possibly a different source of vacuum for your instruments and likely generator regulator.

[Bruce Fenstermacher]

To convert back you remove all pieces of the conversion. You attain all original parts and install them. Your mechanic fills out a 337 for a major alteration stating the STC has been removed and the aircraft returned to original configuration and submits it to Oak City. No further approval is required as the TCDS is the approving authority.

Big pieces you will need will be the engine and accessories, baffles, carb air box, motor mount, prop and spinner.

I wouldn't do it. I'd either stick with the 0-340 or find a way to install a 0-360.

[blueldr]

I would sggest that if you have a Doyn conversion, live with it or trade it, Going back to stock will be prohibitively expensive for the value of the end product.

[c170b53]

This is a tough one. I'm in the process of doing the same thing and the only thing flying, is money out the window.
In my case I bent my engine mount ever so slightly but because its a Doyn who has a jig to make it right? Thus I'm somewhat forced to go back to stock or go to a bigger engine (from an 0-320 to 0-360).
The Doyn problem really revolves (ouch) around the prop. The STC calls for a steel hub which may be hard or very expensive to find. I had a one time for a compact but when I damaged it I needed a new one. Unfortunately because the prop is not a run of the mill, its very expensive hence now I'm left wondering whether its cheaper to find an entire aircraft or do the conversion which might end up costing the same thing.

[bagarre]

Anyone looking to convert back, I have a 440 hour C-145 that could be had for pretty cheap.

[beaverbill]

My 52 B model has had the Doyn O-340 conversion since it was done in 1957 by Cordova Airlines, who owned the plane originally. Works good, lasts long time, as they say. If you do decide to restore your airplane to its original engine configuration, or some other installation, please let me know. I might be interested in your engine just for a spare. As was noted in another thread, Lycoming does not support the O-340 with such parts as are unique to the series.
As for the Hartzell propeller, I can recommend Northwest Propeller Service in Puyallup, WA. (253) 770-7400 They were able to find enough airworthy parts to build up a prop for my plane a few years ago. And they have been good folks to do business with.
Bill