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Fitting an O-360 into an RV-8 O-320 cowl

humptybump

Well Known Member
For those who were not aware, Vans Aircraft created a different cowl for the O-360 and the O-320. While there are not many RV-8's with an O-320 there are fewer still with an O-320 and the O-320 cowl.


Anyone who has this combination and wishes to upgrade to an O-360 should plan to get professional help ... preferable of the psychiatric kind.


I am thankful to say I traveled this unimproved runway and and emerged from the darkness with my wheel pants intact.


I'll be writing about it on my blog. Here is a short introduction to the process.


http://elder.ninja/blog/p/7504


I'll add to this thread with a couple more updates as I write up the gory details.


For the curious, here is the decision flow I went through ... (albeit not in a linear path)

o320-o360_decision_diagram.jpg
 
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I used a 360 cowl for my IO-320 installation. The 360 cowl is about 1.5" deeper at the chin scoop than the 320 cowl.
 
Been there, done that. Actually, have been thinking about stepping up the size once more to a -540 or something like that. So the pain isn't permanent. It'll fade.
 
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Custom O-360 airbox for an O-320 cowl

This is how the "magic" happened ... it's a bit like making sausage.

I've finally sat down and written a blog post that describes how I used a 3D printer to create a mold for a fiberglass and carbon fiber airbox. The airbox takes the same filter as Vans supplies for IO-360 installations. The airbox fits an O-360 with an MA-4-5 carburetor within a RV-8 with an O-320 cowl.

IMG_1225-575x431.jpg


The airbox and engine now has 5 hours and is performing very well.

Below is the a link to the blog post which has more (and larger) pictures. The blog post also has links to PDFs of two important internet resources which helped my with both the design and fabrication.

Blog post: http://elder.ninja/blog/p/7512
 
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Airbox

I had a chance to see that airbox up close. The quality is superb. He described how he printed a mold then remove the mold with heat. I plan to learn more about 3D printing.

I am courious of your impression of your airplane with the new engine. Handling, performance, range?
 
I am curious of your impression of your airplane with the new engine. Handling, performance, range?


I'm still in the engine break-in phase. That said, its an RV-8 with a 180hp O-360. It's probably just like all the others. I'm just joining a well populated club. :cool:



Of course, being able to directly compare the same airframe with a 150hp and now with 180hp, it’s a different airplane now.


Not only is there 30hp more but there is a whole lot more power on take off because a 2017 Catto is a very different design than a 2012 Catto.



IMG_1493-575x399.jpg
 
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Been there, done that on a 6. Swapping the scoops was not that bad, once you spend some time thinking about how to make it look seamless.
  1. Use a die grinder with cutoff wheel to cut off old scoop with smaller "bite" than new scoop flange
  2. Make a bunch of 1" square aluminum "washers" with a 3/32" hole in the middle for a cleco
  3. Trace new scoop outline onto cowl (centered)
  4. Enlarge the "bite" in cowl to the line traced above
  5. Use 15 or so of the two "washers" sandwich and cleco spaced a few inches around the cowl in the cut line to hold the scoop in place and flush with the cowl
  6. Bond together on the inside using fiberglass patches between the washer clamps
  7. Remove the washer clamps and build up the joint
  8. Fill the gap and finish
Build a new airbox per the O-360 instructions.
 
Mike, there were times when I considered cutting the pretty painted cowl. There were also times when I considered reinstalling the O-320.

Ultimately, the airbox was the solution as it left the finished airplane unaltered.

Of course, had I known there was such a thing as an RV-8 O-320 lower cowl and how it differed from the O-360 lower cowl, I probably would never have started the engine project in the first place.
 
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BTW: if anyone has specific questions regarding the use of 3D prints as molds for fiberglassing, feel free to reply here or as a PM. I'm sure I didn't include all the details in the blog post.
 
The engine break-in is done (or nearly so). The last test was a simulated cross country flight of greater than 300 nm to test the air box within a heat soaked engine compartment. Everything checked out.

Time to get back to my typical mission of long XC legs.

It isn?t the fastest RV-8 but it is now ?in the pack? with typical ?Vans numbers? and I?m very happy with the new economy cruise settings.

It?s like getting that RV Grin all over again.

Thanks to the vast quality of data stored in these forums and special thanks to DanH for reviewing design ideas and responding to emails.
 
Glen --so glad you are flying and comfortable again!! Having seen what you were doing, its alot of work but it looks like it paid off.
Tom
 
Update: inspection of the fiberglass & carbon fiber airbox at [a little less than] 50 hrs and it looks just like it did before first flight.

While I don?t have numbers for air throughput, the O360 is performing nominally and the Catto propeller matches the parameters Craig designed for.

img_4056.jpg


It should a good year for flying ?long haul? again :D
 
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