Unlike 5ZQ, I was not able to set the spinner to .375 high relative 
to the top cowl. With the spinner flush with top cowl, I only had .
25" clearance between the inside of the cowl and the ring gear.

Angier,

 

Hmmm, another tight area - how about the distance from the ring to the lower cowl? 

 

I have a harmonic damper on the flywheel that sticks out in front of the flywheel about 1.5 inches and is a much smaller diameter.  Mounted on a bolt at the forward edge are some area washers for prop dynamic balance.  The outer edge of the washers were filed down so they stick out only about 3/16 inch from the outer edge of the damper.  In a Cup race while on descent to a checkpoint, a canard suddenly appeared below and in front of me requiring an abrupt pull-up - abrupt enough to have those balance washers scrape on the bottom cowl and crack the paint on the outside.  Remember I have the soft engine mounts with the bottom shimmed out 1/4 inch. 

 

Would the flywheel have hit? - I don't know, the washers hit first.  Make sure there is enough room around the engine to allow for movement.

 

Also, my cowl is fastened with Camlocs - a nice clean way to attach things.  There is a drawback.  Because the Camlocs are spring loaded, the cowl can move somewhat.  I have always been intriqued by the sliver of bug goo (1/2 inch max at the top) on the forward face of the cowl behind the spinner.  The bugs can't make the turn but my cowl can move up far enough in flight to expose that edge because of the high pressure on the bottom, the low pressure above the top and the puffing out caused by the upper cowl cooling air pressure that makes the whole contraption look like Louis Armstrong's cheeks while he is performing.

 

PS:  For those safety minded folks, just moments before the encounter I had announced my position and intent as the race rules required.  The plane I almost descended into had been flying below the VFR rule's limiting altitude and hadn't announced his position.  He may have had his transponder off or was too low for a request/reply blip since I received no alert from my traffic warning device.  These days, the slower airplanes do not depart first.