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Thread: O-290D to O-290-D2

  1. #21
    Steve Pierce's Avatar
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    Default Re: O-290D to O-290-D2

    My parts manual shows solid tappets on the D and hydraulic on the D2 which matcheswhat I have worked on. I will have to look at the operators manuals and see the hp output at altitude. I operate an O-290-D2 on a PA16 and runs great, not near as good as my Dad's when it had the 150 hp O-320 and now the 160 hp but the price was right and more power an easier to maintain than the O-235-C1.

  2. #22
    Vagabondblues's Avatar
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    Default Re: O-290D to O-290-D2

    I think that the hardest part of converting in the certified sense would be accurately cross referencing the changes between the models. With that in mind and of course having an 1973 edition 290 series parts manual that describes what changed made me curious. The crankcase differs in increased necked down stud sizes , bore size of the propeller hydro control was also increased. But there was also one change that really surprised me. Lycoming changed the bore size of the conical mounts from 7/8" to 1". The change was accomplished on SI No. 1007. Wasn't that a problem that some people are having finding the correct rubber engine mount bushing? Differing sizes of bore but same part number, something like that. The crankshaft parts numbers also are different, but the D2 has a larger oil transfer tube in the pilot bore, probably to match the increased bore of the hydro control in the crankcase. Is it possible that some people are confusing the hydro control for the prop with the hydraulic lifters? The camshaft is also different and with its current price it should considered to be the death blow on converting a 290D to D2 and life to upgrading to a 320.

    There was an article about Lycoming power at altitiude in the CUB Clues #163 dated March /April 2011, author unknown. In the article, as compared at the same altitude, same prop load, same RPM there is about a 4% difference between the 290D2 and 320A. 102.80 HP for the 290D2 and 106.96 HP for the 320. That is perfectly inline with the 5% increase in bore size (volumetric efficiency) 290D2 4 7/8" bore and the 320 with 5 1/8" bore. Anything else would be impossible. The biggest difference is in the weight, 1.54 LBS /HP for the 290D2 and 1.81 LBS/HP for the 320. That is about a 15% percent increase, you will have to decide if that would change real world performance
    Last edited by Vagabondblues; 02-09-2018 at 09:58 AM.

  3. #23
    Steve Pierce's Avatar
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    Default Re: O-290D to O-290-D2

    A friend just bought an L21 Super Cub with the O-290-D2 while rebuilding his 160 hp L21. He say the difference is like flying the 160 with a 250 lb guy in the back. The 135 hp will get in places he can't get out of where that is not the case with the 160 hp.

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