Thorp Air Command - T18.net

Hi all. I found a t18 that used to have a 0360 mounted up front that I am looking at buying and mounting a 0290 D (G). I keep going down rabbit holes so I thought I would ask this find group of Un opinionated Thorpies. I have been creeping on you all for years dreaming of being one of you.
Has anyone done this before? I know usually it is the other way around but it is all about the Money. If I had the money I would buy one of the fine examples that are on Barnstormers.
Let Me know.
Be and Fly Safe!
Dave- Spokane Valley

Welcome to the forum! I don't know anything about the conversion although I have researched putting a 320 in mine because of the trouble I have with getting carburetor dialed in and the cost of finding parts on the top overhaul I just did. Parts are scarce and expensive so make sure you have a near zero time 290 in great condition. Quite a few of the 360 parts will be similar to the 320 but not at all the 290. That might be a better option on cost to install. Plenty of 320 in good shape for a good price.

I have a budget thorp 290 so I know the struggles. Good luck!

My T18 originally had an 0-360, then an 0-290, now it has an 0-360 again. Just get the 0-290 motor mount and it should slide right on, and then hang your engine. I didnt have to redo/change any cowling/cheeks when I made the engine swap. It all fell right into place.

Lou has a 0 time 0 290 for sale
Phil
118BC

Be sure to do a good weight and balance. Most O360 birds have some weight in the tail. Gear and mount should be the same.
Cubes

Wonder what he wants for it? I have a couple of possibles. One in Tricities Wa (D) and a converted (G) in Bc. They have both been sitting for years. Glad to know about added weight and that i shouldn't have to change the engine mount.

you will have to change the motor mount, but that's very easy. 3 bolts and the 0360 mount is off and then slide on the 0290 engine mount.

Lycoming engines use a few different mount types. You should know what type the original O-360 had.
The original for aircraft is called the Conical Mount, sometimes also called a Straight Mount because the 4 mount bolts are parallel to the crankshaft.
O-290 G engines are similarly 'straight mount' but do not have the conical shape bores to accept rubber mount cushions. (Just straight bolt holes)
I have a T-18 with a John Thorp designed mount for O-290G. It's an aluminum plate collar that bolts to the engine, and 4 rubber aircraft type mount cushions connect this collar to the welded tube mount.
The second Lycoming type is called Dynafocal, with these, the mount ears are partially shaved off and the bolt holes are drilled inward toward the center of mass of the engine. The engine mount is made of a steel ring with mount cups to hold the rubber cushions at an inward angle for the mount bolts.
Switching engines from Conical to Dynafocal or back would require a complete new mount. Switching from a Conical to a G mount might be easier, or try find a G engine that has the mount ears bored to conical.
Aw heck! here is a link that better describes these mounts:
https://www.experimentalaircraft.info/a ... mounts.php

_________________
Scott Emery
EAA Chapter 326
T-18 N18TE

Scott is right about the mount. I should not have added that. We have both mounts available.
Cubes

and just an FYI for anyone who cares....and to further complicate things, the Type 1 Dynafolcal Mount has 30 degree offset mounting pads that focus on the center of mass of the engine as Scott says - there is also a Type 2 Dynafocal mount for some IO-320s and 360s that are 18 degree offset pads that focus on the front main crank bearing. I kinda sorta got it ciphered why they do that. Theoretical Engineering Witchcraft Shit. (TEWS)

_________________
Fraser MacPhee
N926WM
Serial #279-1
Angel Fire, NM (KAXX)

I asked John Thorp why Lycoming went to the dynafocal engine mount and he pretty much agreed with what Fraser’s conclusion was. He said he thought it was mostly sales propaganda.
Steve

We have Type 2 and Conical only. Very few require Type 1
Cubes.

Personally, I think the only reason they went to dynafocal mounts was to make it harder to install the engine.

_________________
Thorp T18
O-320-B3B (160 HP)
68x74 Sterba Propeller

"The joke in aviation is, 'If you want to make a million, you'd better start with £10m.' " -Bruce Dickinson

Hahaha. Agree Jeff! I think I said the type 1 vs 2 backwards. Too foggy these days. Sorry about that.
Cubes

O-290's are great engines if you want a light aircraft and can live without all the stuff I see most RV builders stuffing in their planes. I have 8.5:1 piston sets complete with pins, rings and thrust buttons that will give 150hp for takeoff from a O-290 and not increase the fuel burn at cruise settings. Aside from new cylinders all other parts for O-290's are pretty available. They may be parts from O-235 or O-320/360 or whatever but they can plug in and play with the O-290. These are experimental aircraft and as such we have the latitude to do what is safe to keep them flying.