Need help with ID of aircraft parts found in Hawaii

[Son of Gort]

Greetings folks,

I am currently in Hawaii for work and during my days off I have been spending much time in the mountains hiking.

During one of my excursions on a seldom used and overgrown trail just north of Honolulu, I came cross several pieces of what I believe to be a destroyed aircraft. There were 4 pieces found in total and I can't be certain as I am no expert but I believe there is a good chance they are Japanese. One of the pieces is the cylinder head from a radial engine and it is that part which I have spent the most time researching.

Before I go further, here are the pictures:

I apologize if the pictures are blurry but these were actually taken from videos that I took of these parts (so they could be seen from multiple angles). The fact that these parts are spread out over a jungle valley over a span of over a mile and the fact that the cylinder head is removed from the engine block leads me to believe that this aircraft exploded mid-air rather than crashed and so I'm not thinking they are civilian in nature.

The cylinder head intrigues me most as it is the most readily identifiable. I compared it with any images I could find of the engines that were in any other aircraft which took part in the Pearl Harbor attack and it doesn't resemble the head of any of the planes shot down over Hawaii back then. The P-36 Hawk had a Wright XR-1670-5 Whirlwind:

Above is a J-6 Whirlwind but you can see the head configuration is not close to what I found.

The Wildcat had a Pratt and Whitney Twin Wasp:

Also not close.

The P-40 of course had an inline engine so it's not from one of those.

All the B-17s destroyed on that day to my knowledge managed to land before being destroyed so I don't believe it came from one of those.

I also looked up the engines for all Japanese aircraft that took part and they all had engines from Nakajima (Sakae, Model 11, Homare, Hikari...)

Here is a picture of the Homare engine:

That area where you can see the rocker arm over the valve spring is very similar to what I've found. The spacing and angle between the intake and exhaust valve sections is about right also. I found some pictures of the other Nakajima engines present that day and they are far closer to what I've found than anything made by the U.S.

In addition, of the pieces containing the skin, none of the exterior sections contain any round headed rivets, they are exclusively flush rivets. I know the Americans used flush rivets, but not to the extent the Japanese did. Also, although paint will wear off after years, there is no evidence that any of these parts were ever painted (I believe the Japanese forwent paint in some situations in order to save weight as well).

I could find no serial numbers, writing or symbols either.

I left all of the pieces where I found them.

I then contacted the Aviation Museum on Ford Island and they said they forwarded the videos I sent them to their curatorial dept. but it has been weeks and they have made no attempt to respond to my email or voicemail.

I apologize for my rather long post but this has me very excited and I was hoping someone here more knowledgeable than myself could help to identify these pieces.

Let me know what you think.

Regards,

Gort

 

[GrauGeist]

If I recall right, Rasmussen and three other P-36 pilots engaged 11 A6Ms to the north-east (near Kaneohe) downing a few.
Is this the area where you've found the debris?

 

[MiTasol]

You are right that it is a radial engine but I cannot see anything that specifically identifies what engine type. The photo quality is fine. The thermocouple fitting in the first photo strongly suggests an American engine but the general corrosion makes other details less definite. I am not sure what year that style thermocouple fitting was introduced but that would set a not before date.

The vast majority of P-36 aircraft actually had Wright R-1820 Cyclone 9 or Pratt and Whitney R-1830 engines so you need to get some good photos of those engines. There are probably at least 50 variants of the Cyclone 9s and they ranged from around 700hp to around 1500hp so naturally there a dozens of cylinder variations. Likewise there were many Pratt variants but I have never seen that style of exhaust on an R-1830. That does not mean that Pratt did not make some 1830 engines with that exhaust connection though. My gut feeling, from the rocker hat, is it is a Pratt cylinder of some sort.

As far as I recall all the R-1820 engines of the ww2 period had four stud rocker hats with sloping rocker hats and that head has a six stud rocker hat with no slope.

Personally I do not think it is a P-36. The ammunition feed chute (in the photo with your shoe visible) does look Curtiss though but other makers ones were similar.

The first two photos show a short stub pipe between the cylinder head and the expansion joint that goes into the collector ring and that normally means you are looking at a front cylinder on a two row engine. Wright engines had a wide variety of exhaust to cylinder connections and a square four bolt fitting like on that head was used on the R-2600 in the B-25 but nothing else jumps out to me as B-25. All B-25s I worked on had rocker hats like the R-1820.

If you go back to the site look for part numbers on the exhaust tubes and on the ammo chute and other parts but the stainless parts are not corroded so easier to find a number. Those will make it easy to make a positive ID of the aircraft type. As a long shot take a selection of US and metric spanners to confirm the exhaust nuts are American or not.

And don't forget there were a lot of other aircraft crashed on that island during ww2 and even post war.

 

[Shinpachi]

The relic is not a Japanese engine as the rocker head has 6 screws. Japanese preferred 4.
Looks like a P&W R-2800 at a glance.

 

[MiTasol]

Yes, that makes sense - last worked on them in 1963. 1972.. The CB16s in the DC-6 had that sort of thermocouple. The -8 in the Corsair had the old spark plug gasket type from memory.

 

[Snautzer01]

Waianae Range ?

 

[MiTasol]

We can rule out the R-2800 as fitted to the P-47 and F4U - three stud rocker hats on both

 

[Son of Gort]

Hello folks and thanks for your replies and insight.

I may have one more chance to head out to the valley and get another look at these parts and try to find some kind of identifier. I will definitely take a better 360 degree video of the head since the last time I was a little too excited and wasn't as focused as I should've been on getting a really good look.

I will keep you folks posted!

 

[Son of Gort]

Waianae Range ?

Ko'olau Range.

 

[Son of Gort]

If I recall right, Rasmussen and three other P-36 pilots engaged 11 A6Ms to the north-east (near Kaneohe) downing a few.
Is this the area where you've found the debris?

It was actually on the other side of the mountains in the valley below. When I crested the tops of the mountains I was looking over Kaneohe. Not a bad view eh?

 

[MiTasol]

Been thumbing through my engine manuals and the only 6 stud rocker hats so far are on the civil CA3, CA15, CA18, CB3, CB16 & CB17 series engines which obviously that is not.
I dont have many later R-2800 manuals but will keep looking. Might have to check out AirCorps library.

 

[MiTasol]

AC show the -34 has six studs so now what aircraft had engines starting around that model or maybe a little earlier. F7F and F8F may be right period

 

[MiTasol]

Not F8F. No interconnect tubes

 

[GrauGeist]

It was actually on the other side of the mountains in the valley below. When I crested the tops of the mountains I was looking over Kaneohe. Not a bad view eh?

View attachment 658406

Amazing view!

 

[MiTasol]

not A-26

 

[MiTasol]

Not F4U-1 Interconnects but wrong attachments (clamps not studs) and wrong rocker hats.

Possibly F4U-4 as has interconnects though not shown in the IPC but referenced in the E&M. Three stud attachment. I had presumed that your wreck had four stud attachments but now I suspect three stud. I do not have a -18W manual but maybe someone else does and that will determine if 3 or 6 stud rocker hats. Does your film show the exhaust connection to the cylinder better? If so 3 or 4 stud attachment? This aircraft uses the correct type of thermocouple as well. It appears the only thing in doubt is the number of studs holding the rocker hats.

 

[ThomasP]

I remembered reading (a long time ago) that there was a crash of an R6D aircraft in the mountains of Oahu in the 1950s. The R6D used R-2800 engines, but I do not know which model.

When I did a search for R6D crash in Oahu I ran across the following:

"ASN Aircraft accident Douglas R6D-1 (DC-6) 131612 Honolulu, HI"

I do not know how close the crash site is to where Son of Gort found the wreckage.

If someone can find out what model of the R-2800 was fitted to the R6D-1 that might tell you if this is from that crash. All I could find is that there were at least 2 different models of R-2800 used, at least one model for the DC-6A civil and military variants, and a different model for the DC-6B civil variant (and military variant?? I could not find info on any DC-6B military variants).

PS Just found the SC for the USAF C-118A, and it says the engine model fitted was the R-2800-52W. But I do not know for sure if the USN R6D-1 used the same engine.

 

[MiTasol]

But the R6D/C-118/DC-6 do not have ammunition feed chutes

 

[MiTasol]

The feed chute does not look like the F4U-4 and -4N ammo chutes though - looks too long for inboard (and has two slots instead of one) and the outboards were flexible with 50 cal and 20mm were all flexible. To me looks like a 50 cal chute but camera angle could be misleading me.
Could be from different submodel though that I have no info on. Could also be from something totally different but still using R-2800

 

[Son of Gort]

Ok so I managed to get back into the valley to find these parts and take more photos/video.

Here are some shots of the cylinder head with what I hope are part numbers on the exhaust pipe.

Let me know what you think:

The part number on the above piece reads: 83145-B

The exhaust pipe did have some numbers and letters on it but it just so happened they were on the side which is bent back against the head and so I could barely get my camera to see them. If only I had my eyes from five years ago with their 20/10 vision I swear I could've read them no problem.

Here is what I was able to capture there:

I believe the stamping reads: 96R67012

Above those numbers appear to be the letters "BUHR" of possibly "BURR" but then become unreadable until the end which appears to read 11 R

This part of the pipe has what appears to read as: (OK
stamped on it but I don't see anything beyond that.

Lastly i noticed this symbol on one of the pipe flanges. I'm not sure if it helps.

I also got some more shots of the ammo feed chute:

This is the largest piece found:

The piece above has a hinge inside of it:

I have a few more pictures but I've run out of space here. I also have a video which is basically the cylinder head from every angle so if there is a specific angle you need let me know and I will freeze frame it for you.

Thanks again for your time everyone!