Hi guys,
IMO the most logical break in process for an ABC/ABN engine is as Dar Zeelon has described in his "tappered bore break in" column[sm=thumbup.gif]. Not every ABC/ABN engine will get destroyed immidiately by fourstroking but the high output tight engines will probably do if fourstroking and running cold for a long time. My friend just bought a new OS46FX and he turned it over the TDC just by rotating the propwasher[sm=thumbdown.gif]. So I dont think his engine needs a break in (to loose to begin with). Good luck.