From: Bob Rickard <r.rickard@rcginc-us.com>
Date: June 20, 2012 7:15:53 PM EDT

IV-P non turbine Fellow Pilots:

I recently received a rebuilt TSIO-550 from Barrett Precision Aircraft in Tulsa.  Was quoted 9 weeks to overhaul, took 5 1/2 months (but that is another story).  The good news is that the motor is back in the airplane, and looks and runs fantastic.  My problem is, its running hot inside my airplane.  The bottom line is - I am looking for suggestions on how to solve the problem described below- I have about 600 hours in my airplane on the previous engine, have taken the GAMI course, and run LOP cross-country almost exclusively.

Motor installed and test run.  Every effort to try and install exactly like it left - only exception is spark plug wires installed below the air tubes (they were on top before - I don't know why the mechanic put them underneath). No problems with Cowl off.  First flight - one pattern only - Max MAP was set too low, low fuel flow - fixed.
Next flight - 10 minutes - Cylinders 5 and 6 temps run away hot at 38.5 MAP and 45gph.  Must retard throttle to less than 25gph (25ish MAP) to keep under control.
Third flight  - after checking baffling for hours and scratching head - same deal.  Fly for 1 hour full rich at low power settings.  Motor very smooth and happy at low settings, but as soon as throttle pushed in, cyl's 5 and 6 climb at about 1 degree per second - power always retarded not to exceed 390 and cool down in the 350-360 range before trying to push up power again.
Fourth flight - today - a 2.3.  Takeoff WOT and full rich.  Can't get above 3000' agl before having to pull power for cal 5 and 6.  Pull power to 25gph/25 MAP/Full rich and slowly climb to 10.5k MSL.  Fly there for a while, cylinders all look great in the 340-350 range.  After an hour, try full power climb, have to stop within 1500' of climb.  So then I leveled out, and set my typical speed cruise LOP mode to try something different - 34MAP, 2500 RPM, 18-19 gph.  Motor is very happy.  All EGT's normal (actually less than previous engine by almost 100 deg), CHT's all between 340-365.  I climb with this setting to 16.5 and cruise for another hour, no problem.  Return to base, set full rich/2700 rpm, and land normally.  At retarded power settings in the pattern, motor stays cool and happy.

So what to look at?  New motor mounts make the engine sit noticeably lower in the cowl, and we are checking the rear baffling to make sure there is a good seal, but would that affect the front 2 cylinders (5 and 6)?  Every other indication (including the other 4 cylinder temps) are totally normal.  Any other suggestions out there to look for?  Appreciate your experience

Bob Rickard