aspeed

I always use one head shim, unless it is hitting the head. All the nitro you have is good. For just speed, a 4 or even 5" pitch is good. Maybe a 5-4, or the electric APC 4.75 - 4.75 and wear a face shield. I just ran up an .06 c/l one the other day with a reduced hole in the carb, it just didn't run with the .200" hole. The 4 & 1/4 - 4 APC was up around 26,000 rpm. with no muffler, the .049 was around 24,000. I think the .109" hole I used would be about equal to the RC carb. This was 10% no muffler on the older .06, not the Big Mig. I just use whatever plug is around, as long as it is not a 1/4 - 32 conversion plug, they all seem similar except the old Babe Bee low compression plugs. The Norvel, TD, or Merlin ones seem about the same as the one I think is the Galbreath head. (it just came on a motor I picked up at a swap meet so it is just a guess) Get out your tach, and experiment to really know. It is hard to get speed #s on an rc, but I would think about 20 to 25,000 rpm on the ground would be what you should aim for. Any higher and you may need parts. Having said all that, my Ace simple 400 keeps me thinking fast with just a 5.5 - 4" black Windsor prop on it, likely revving slower than 20,000. It is at my limit of flying ability right now, yours will likely be higher. As far as the screen, Just blowing through it, it seemed to restrict the air more than the .200" venturi hole, but less than the .109" but I took it off just in case.