Thorp Air Command - T18.net

I understand that quite a few 0290s had 0320 crankshafts and cylinders installed. Does anybody have the instructions for doing this available? Some machine work on the case? Any other parts interchangeable?
Thanks,
Daryl

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darylat8750ft

My O290-G has a O320 sump and a MA4-SPA carb not sure of any other O320 parts.

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Bruce Finney
N18JF T-18C #262
Yelm, WA USA

My 0290D has an 0320D crankshaft, no modifications were required.

Dave

Thanks

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darylat8750ft

Further on this topic. I understand there are 2 & 4 front bearing halves on different cases, depending on fixed prop on varible (seem to remember four for fixed). My question:
1. are all cranks interchangeable (JT was using 235,O290,O320,O340) in the GPU cases with some case clearancing.
2. Is there something unique about the O320 h2ad crank.

My reason for asking is I found a running H2AD, real cheap. Sell off the extras and get a free crank. Seemed like a possible source for GPU crank upgrade.
FWIW, the H2AD will not fit to the T18 Dynafocal mount without alteration, the accessory case is to high at the top.

Bob,
I just majored an O-320-H2AD and converted it to an IO-320-H2AD. There is very little from an H2AD that fits any other O-320. Even the valve covers are different. As I recall, the gear and mounting are different on the crankshaft. Call a Lycoming tech rep to be sure before you buy it. By the way, the engine is going on a Bucker Jungman.
Steve Hawley

*** admin posted for Steve Hawley ***

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Forum Administrator

I have an O-290G conversion with an O-320 crank, sump, carb and accessory case.
It has two Bendix mags, a Vacuum pump, and a fuel pump. It has late O-290 aircraft cylinders. It still uses a solid cam.
I have another O-320 parts question:
Does anyone have experience or a story about boring the case for O-320 Cylinders?
Also, I see on the airboat site, a fair number of O-290 conversions with GO-435 angle valve heads. Presuming O-320 cylinders are fitted, then O-480 Narrow Deck Angle Valve cylinders would make the most exotic O-290G conversion with the stock stroke?
Would longer base studs be required to clear the cylinder flange clips?
I'm not building any more hot rod car or boat engines! I'm Not! I'm NOT!!

I just read in NL 22 Lou Sunderland calls an O-435G with angle valve heads an O-290G-Whiz
SO fitting O-480 angle valve cylinders makes it an
O-320G-Whiz...?