Howdy all. Glasair driver here... Lycoming IO-360 B1A. 800 since O/H. Bendix mag on the left, Lightspeed EI (Hall module) on the right. I have an interesting dilemma that is confusing numerous mechanics. For many years, my engine ran fine... EGT's around the 1370/1380's, and CHT's in the 380's in all 4 cylinders. All consistent. I run about 40 degrees ROP, for smoothness and engine longevity. But over the last 4-5 years, both EGT's and CHT's have started to climb. EGT 1400's/high 1300's, and now all CHT's in the low 400's. Recently had a scare, where #4 (then #1) CHT's suddenly climbed to 500! Yikes. Reduce power, then back to airport. JPI EDM700 went bonkers. Turns out, it was a "MUGS board" that needed to be replaced. But with 15 years of uninterrupted service out of it, who's complaining! However, my CHT's are still high... 405-420's all across. EGT's are higher (1390/low 1400's). My main concern is toasting pistons with these high CHT's. Everyone seems baffled. We put in an O/H Precision fuel servo (previous Bendix was last checked in 2002!). Babyfood jar test showed same fuel levels in all. Overhauled the divider. Cleaned all injectors. Timing is spot on (25 BTDC). Intake testing showed no leaks, but we replaced all 4 hoses and gaskets, as the originals were getting pretty dry and cracked. Exhaust had some leaks in #1 and 2 (flanges), so repairing those now. No evidence of baffling issues.
My mechanic is suggesting we check the valves/possibly ream them/check for wobble. Then if that doesnt work, retard the timing to maybe +/- 23 degrees BTDC or so (power loss should be minimal to not noticeable, based on my limited mechanical skills).
Suggestions? Thoughts? Comments? I don't feel comfortable with these CHT's.
Many thanks!!!
My mechanic is suggesting we check the valves/possibly ream them/check for wobble. Then if that doesnt work, retard the timing to maybe +/- 23 degrees BTDC or so (power loss should be minimal to not noticeable, based on my limited mechanical skills).
Suggestions? Thoughts? Comments? I don't feel comfortable with these CHT's.
Many thanks!!!