Sorry for the length of the post but I wanted to get all the info out at the start.
Recently my engine developed a slight roughness and change of tone in flight along with a slight loss of power. *Time for annual condition inspection anyway and when I pulled the plugs the mystery began. *Both plugs on #3 cyl were very sooty, not oily.
History. *I am not the builder. *This aircraft (RV-4) was built in 2001 and had 300 hrs TT when I purchased it, I have put 200 hours on it in a little over a year. * *Uses almost no oil (a little over a qt between oil change). Plugs burn very clean and very uniform, compressions are great, all in all a good engine.
Setup. *Aero Sport Power Lycoming O-320 D2A, Marvel/Precision MA-4SPA carb., Catto prop, Slick Mags, Elec boost pump (no primer lines to any cylinder), 500 hours since Aero Sport Power o/h. *4 pipe Vetterman exhaust. *Spark plugs Champion REM38E, single cylinder (#4) egt/cht (I know I need a multi channel ems).
Performed these tests/checks/inspections to no avail! *Found no problems and the sooty plug problem remained. *Plugs soot up with just a short ground run up, mag drop 50 rpm on each mag. *Performed a run up after each of these tests.
1 bench tested, gapped, and rotated plugs.
2 tested ignition harnesses (also tried different harness)
3 compression #3 76/80 (others were 75-78/80)
4 dynamic compression (automotive) 150 on all
5 removed mags and did 500 hr inspection/cleaning, no indications of any problem. Remember a mag drop of 50 on both mags.
6 checked for induction leaks. *None
7 checked for sticky exhaust valve, broken valve spring, bad lifter. *None
8 removed #3 jug, checked valves, seats, piston, cylinder, head, cam, lifters again, rings, oil control ring, push rods, rockers, valve travel. *Nominal
9 pulled a vacuum on the intake to check for possible crack in sump
10 did a run up using only the left mag. *#3 plugs sooty, others very clean for only running on one mag!
11 pressurized carb with boost pump, no leaks or seeps.
12 don't know what else to do! *Several knowledgeable A&Ps at my airport are stumped on this problem.
13 have not tried a different carburetor, yet.
All work done by or with the supervision of my A&P.
Thanks in advance for your consideration on this baffling problem.
Recently my engine developed a slight roughness and change of tone in flight along with a slight loss of power. *Time for annual condition inspection anyway and when I pulled the plugs the mystery began. *Both plugs on #3 cyl were very sooty, not oily.
History. *I am not the builder. *This aircraft (RV-4) was built in 2001 and had 300 hrs TT when I purchased it, I have put 200 hours on it in a little over a year. * *Uses almost no oil (a little over a qt between oil change). Plugs burn very clean and very uniform, compressions are great, all in all a good engine.
Setup. *Aero Sport Power Lycoming O-320 D2A, Marvel/Precision MA-4SPA carb., Catto prop, Slick Mags, Elec boost pump (no primer lines to any cylinder), 500 hours since Aero Sport Power o/h. *4 pipe Vetterman exhaust. *Spark plugs Champion REM38E, single cylinder (#4) egt/cht (I know I need a multi channel ems).
Performed these tests/checks/inspections to no avail! *Found no problems and the sooty plug problem remained. *Plugs soot up with just a short ground run up, mag drop 50 rpm on each mag. *Performed a run up after each of these tests.
1 bench tested, gapped, and rotated plugs.
2 tested ignition harnesses (also tried different harness)
3 compression #3 76/80 (others were 75-78/80)
4 dynamic compression (automotive) 150 on all
5 removed mags and did 500 hr inspection/cleaning, no indications of any problem. Remember a mag drop of 50 on both mags.
6 checked for induction leaks. *None
7 checked for sticky exhaust valve, broken valve spring, bad lifter. *None
8 removed #3 jug, checked valves, seats, piston, cylinder, head, cam, lifters again, rings, oil control ring, push rods, rockers, valve travel. *Nominal
9 pulled a vacuum on the intake to check for possible crack in sump
10 did a run up using only the left mag. *#3 plugs sooty, others very clean for only running on one mag!
11 pressurized carb with boost pump, no leaks or seeps.
12 don't know what else to do! *Several knowledgeable A&Ps at my airport are stumped on this problem.
13 have not tried a different carburetor, yet.
All work done by or with the supervision of my A&P.
Thanks in advance for your consideration on this baffling problem.