Mystery Japanese Radial Cylinder

[Artificat]

I am trying to identify what engine and possibly which aircraft this cylinder would have belonged to. It looks as though it is produced by Mitsubishi due to the presence of the three diamonds, however the cooling fin arrangement doesn't match the Mitsubishi Kasei, the Nakajima Sakae, nor the Nakajima HA-5. Does anyone have any clue what it could be? Supposedly this is an A6M cylinder that was brought back from a scrap dump at Kiska Island, but I have my reservations.

 

[Capt. Vick]

Are those all inspection stamps?

 

[Artificat]

Are those all inspection stamps?

Yes I believe so, though I am not certain as resources for Japanese aircraft inspection stamps seems pretty rare. I took a picture of the opposite side. I did find a few more numbers around what I think is the intake port, and the intake valve and rocker arm also had some markings. I updated the original post with these new images. Also the bore is 5.5 inches which would lead me to believe that this is either a Mitsubishi Zuisei or Kinsei engine, however the fin patterns don't seem to match for either radial.

 

[Shinpachi]

As you guess, the engine would be either Kinsei or Zuisei.
Cooling fin design has nothing to do with the designation.
As another clue, stroke 150mm was for Kinsei as well as 130mm for Zuisei.

If the stroke should be 160 or 170mm, your relic would be a very historical model "Shinten" as this was almost experimental model with production quantity only 119 sets. Mitsubishi A20 experimental engine (18 cylinder type of Kinsei) was also designed based on the bore/stroke 140/150mm for your reference.

 

[Artificat]

As you guess, the engine would be either Kinsei or Zuisei.
Cooling fin design has nothing to do with the designation.
As another clue, stroke 150mm was for Kinsei as well as 130mm for Zuisei.

If the stroke should be 160 or 170mm, your relic would be a very historical model "Shinten" as this was almost experimental model with production quantity only 119 sets. Mitsubishi A20 experimental engine (18 cylinder type of Kinsei) was also designed based on the bore/stroke 140/150mm for your reference.

Thanks for the help! I am comfortable with measuring the bore, but how do I accurately measure the stroke of the cylinder without the rod, piston, and crank?

 

[Shinpachi]

When the bore/stroke for Kinsei is 140/150mm, cylinder length would be around 235mm.
When the bore/stroke for Zuisei is 140/130mm, cylinder length would be around 210mm.

 

[Artificat]

Thanks for that fantastic diagram Shinpachi! I measured the cylinder length and it was 236mm, which confirms that it is a Mitsubishi Kinsei cylinder. The history that came with the cylinder claims it was a Zero cylinder that was recovered from Kiska Bay and put on display at a base on Adak Island. My research has found that two Aichi E13A wrecks were taken from Kiska and displayed at Adak, which could be the source of this cylinder as the Aichi E13A used the Mitsubishi Kinsei engine. The "Zero" reference in this cylinder's history could be in regard to the E13A's designation "Navy Type Zero Reconnaissance Seaplane".

This is one of a few photographs I have found showing the aircraft at Adak.

Thanks for the help everyone! I have included all of the information I have into this post so that it may hopefully help someone else in the future.

 

[Shinpachi]

Congrats, Artificat.
Spark plug position of Kinsei model 43 for the E13A seems to coincide with your collection.

 

[kalani]

Are those all inspection stamps?

Definite Mitsubishi "triple diamond" inspection stamps among the group.