cwelkie

Beautiful work as always George!

I like your idea of using a printed holder for metal parallels.  This avoids the pitfalls of "plastic variability" due to heat, wear and compression when used for the actual spacer.  I may have to print a couple holders for a set of 3" ground parallels I've got.  They usually get used for this purpose with magnets but a 3DP holder would be less fussy.

I too have learned by doing.  As mentioned above, creating parts I'm interested in is much more interesting than a tutorial.

I use Alibre Atom 3D and it does all I've wanted in a CAD program for my model engineering and 3D printing.  I've used Alibre for years (even prior generations/owners) and have only good things to say about it (as a non-professional).  The greatest advantage in my opinion is the single up front cost - no subscription; no cloud.

I have built this model from some of the original castings.  It too was built with a Hall Effect sensor; in the distributor.

The engine ran well.  I think blaming the intake system may be chasing at ghosts.  Especially given the evidence of a large enough backfire to throw a prop.  I believe my engine suffers from low compression due to leaky valve seals.  This may be in due to, in part, the separate seats and my lack of experience when building it.  (This was my first 4 stroke cycle model engine ... go figure.). Never did around to tearing hit down to resolve the compression - other projects beckoned.

Your Aeronca will run once you work through the possible causes.  It's not a powerhouse but it will run just fine.

This is great news (to me)!  A huge thank you to the person(s) that saved Marv's work from the dust bin of "progress'.