After making these mods, I decided to run the engine again with the cowl removed.  I instantly gained ~200 more RPM and was able to continue to lean the high end out with continued performance gain.  Ultimately getting ~6130 RPM +/- (almost 400 more RPM than before).  This is more like it!  I did have to richen up the low end a little, not unexpected with cranking down the high end.  

Now it's interesting that when I put the cowl on the day before that the low end became lean and the high end became rich.  Making this firewall and vent mod basically did the same thing with the cowl off.  So, I'm hoping that with the cowl on I don't loose anything but maybe gain?  Will have to wait and see as it was getting dark and I didn't want to mess with it anymore.  

Hole in firewall for the carb intake.

Vent tube

This is more like it!

Wanted to document this...paperclip through the bolt heads.  They are not going to turn out.

Well, the good news is I figured that out .  Hopefully the weekend will bring resolution to all my challenges!

Ryan

I opted for a taught paperclip instead of wiring the screws as you show.  I figured as stiff as a paperclip is, if I made it tight so it could not create slack that the screws could not back out.  As a bonus, it is easy to remove and reuse. 

Ryan

Why?  If only I knew.  I do know one thing, we have all been there at some point or another .

Yes, I did figure it out and now all is good in RPM land!  I took the cowl off and went back through my carb adjustment process and now I'm getting ~6300 RPM +/- with a constant hold above 6200RPM.  Throttle transition is instant and idle is smooth as silk.  I didn't get to put the cowl back on and give that a go as thunderstorms were rolling in, but for now I am very happy with the results of my muffler and other mods.

More to come .

  Where did you obtain and can you provide any further details about it?  Any negatives with it ?

This would allow for a deeper engine on several of my projects which would allow more room for dummy radial, etc. Or in your case, keeping the engine mostly inside the cowling.

  REgards-Mike O

Sierra Giant Scale makes and sells them.  Linky

I contacted them to see if they made one for the DLE and they said that the DA they make was the same and would work.

It is possible it creates more vibration but I have nothing really to compare it to.  I just make sure my prop and spinner are perfectly balanced.  It seems not to have any effect on the engine at low idle or full throttle.

Ryan