Originally Posted by
Pete G
My RV-6 powered by a LyCon IO360-EXP (w CS Prop/P Mags/NGK Auto Plugs) occasionally runs rough at power settings above cruise, eg, takeoff. In several occurrences I have observed the #3 EGT to plummet from ~1300 degs to below 700 degs while the other cylinders were steady around 1300 degs. Reducing power resolves the issue with the #3 EGT recovering to normal. Last occurrence required power reduction to 16 inches MP. I have done repeated ground runs and test flights and have yet to duplicate the problem. Have done full power ground runs on L only, R only, and both PMAGs, all satisfactory. Have replaced plugs only to have problem return. Checked fuel nozzle and spider, no problem found. Have not done Lycoming SB 388C (valve and valve guide insp), may be my next step. Any suggestions? Thanks in advance for your ideas