StanDouglas

I prefer to do my engine cleansing of new engines by disassembly, washing with a solvent, and inspection prior to running rather than hoping any Chinese machining residue will blow out by turning high RPM on the first run. I at least remove the head and back plate of any engine prior to the first run.

I used to replace the C clips and Lock Tite the wrist pins to prevent wear at the piston and wrist pin, but TT has evidently fixed that problem long ago so it is a waste of time.

My purpose here is to present an answer to the original post and to provide the theory behind the current state-of-the-art methodology and thinking behind the theory's of getting more performance out of an ABC racing engine.

It would be interesting to hear what RPM's various TT 40 Pro's are turning and what the original break-in procedure was. I have always followed fairly closely the Van Der Hey procedure and run at least 3 tanks of fuel on the test stand. I do notice that after that it takes a gallon or more of fuel in the air flying before the engine really reaches it's best.

As an aside, I have done some testing with a new bag of 9x6 APC props all on the same day and fuel etc. The results were that the RPM could vary from prop to prop by as much as 400 RPM.
Because of this I have one prop that I have labeled with a marker "test" and I use it only for RPM testing so that I can get a fair assessment of the ranking of my 5 engines.

And other questions to consider, what effect does balancing an APC have on the RPM turned? Anybody done some actual testing, unbalanced and then balanced? How do you balance a prop? Do you go as far as the hub balance 90 deg. relative to the blades? Is there an effect if the nose and mount are not stiff enough from vibration? Do you blunt the prop leading or trailing edges or blunt one sharpen the other?

SD