Please respond to a longer post detailing the issue and answering Bill's questions.
Here’s what happens:
I depart normally. The engine develops 5300 rpm as it should. Moments after takeoff the rpm drops to 5000 rpm and the oil temp shoots way high. Climb speed drops. This is shown in the data boxes copied into the engine data traces below. EGT remains normal.
I land. You can see this in the altitude trace (green) on the bottom chart. I backtaxi and depart again. This time everything is normal, as you can observe in all traces after the 50 minute mark. RPM, climb, and oil temps are exactly where they should be for the conditions at this time of year (cold). The last two times this problem happened (not shown) I did a ground runup to make sure I could achieve 5300 rpm static before I departed again, and I did. Yesterday AM I departed normally, but in the PM the problem recurred at a towered airport. How embarrassing to have the controller ask what’s going on and then telling you to fly safe.
This scenario has repeated itself THREE times. I cannot figure out what’s going on.
Here is some other relevant info:
1. The issue happens with both fresh mogas (all e10 or less) and avgas—I’ve got four tanks and can switch between them. So I’ve eliminated a bad load of fuel. I add Decalin to the avgas.
2 I pulled the float bowls and in each side there was a small amount of very fine particulate, black and shiny. This is pictured in the photo posted earlier. You can see the particulate in the lower right corner of the bowl. The problem occurred again after I cleaned the float bowls.
3. I cleaned the air filters.
4. Lockwood overhauled the carbs—they have maybe 30 hours on them.
5. The fuel pump is new—also thirty hours. I replaced it when I did the rubber replacement, which included all fuel lines, etc. I climb with my boost pump on.
6. I never see any contamination when I sump the gascolator in the morning, and I sump each set of tanks. I have never, ever had any contamination issues and I've flown in some pretty remote places.
7. The oil, oil filter and plugs all have about 10 hours on them. I have an oil consumption issue but I believe that is due to leaky rocker covers. I have disassembled them, lightly sanded them, replaced the gaskets and used Loctite 598 with no improvements. So I am careful to monitor the dipstick.
I remain totally mystified and would be happy to receive any troubleshooting suggestions. It occurred to me that maybe the plugs are getting fouled as I wait for the oil to warm up (12-15 minutes) so the next time I fly I'll do a full power static runup prior to takeoff to see if that makes a difference.
