I have a friend who has asked for my help with his engine run. I thought it would be great to post here and get some good help. Here is what he sent me:
I have a ARF Brodak P40 with a Enya 6001 7mm venturi, 3.5mm enya spraybar/NVA, 6002 head, .012 head shim, 4 ounce uniflow tank, 10% Nitro 22% oil (50/50) syn/castor, prop 11x5-12x6, tongue muffler heavily drilled out. I am struggling with getting a consistent run. It really sounds great on the ground with a 11x7 revup at 7500RPM, or 7350 with a MA 12x6 wood, but wants to run away in the air, the engine really seems to speed up once the plane takes off losing the 4-cycle sound and running lean. When I richen the engine enough to avoid runaway, the plane can barely take off, then once in the air it speeds up and does not do too bad, but impossible for me to predict. I am also having to run the tank very high to even out the mixture while being inverted.
I have experimented with the original 6001 head without .012 shim and 5% Nitro 29% castor, 12x6 prop, It is not predictable, 7250-ish on the ground, it will lean out in the air. I have also tried 0% nitro 25% oil, it acts very similar to 5% stuff.
If I remove the shim with 10% Nitro, the engine will detonate the entire flight, even rich!!
I really think this engine has real possibilities, I think I am just not understanding something.