BLUF: my CHTs are running high in both climb and cruise, and my oil temperature is running almost up to redline.
Rather than piggyback on my detonation thread I figured I’d start over with a new baseline of what I’ve tried so far. Today I flew and tried a 3500’ 2400 RPM lean test I read about in another recent thread about carb nozzle size.
https://apps.savvyaviation.com/beta/shared/flight/6985417/be3f4097-6137-4041-8f38-5053deca4858
You can see the results of that test between 13-15 minutes.
The CHTs at climb out are easy to see in that entire graph. After the lean test I tried a climb to 11,500’ and had to terminate that at about 10,000’ due to oil temperature reaching redline.
What I’ve done so far:
New silicone baffle strips sealed as best I can using a dark hangar with the top cowl on and a borescope to see how it is all sealing up.
Every hole I could find on the baffles sealed with RTV. I used a shop light underneath the engine and hit anything that wasn’t through a fin.
Fiberglass RTV baffle wraps - including checking that I didn’t inadvertently block any fins.
Taping off the gaps between my cowl and the baffles around my Cessna style airbox, at the inlets, and blocking the blast tubes pointed at my magnetos.
Reamed the carb main jet to .1065” and validated float height.
What I haven’t done yet:
Investigate the vernatherm.
Instrument the cowling for pressure differential measurements.
Some basic info for reference:
O-320 with 10:1 pistons
7 row oil cooler mounted on the firewall fed by a 3” SCAT hose tapped from the back baffling wall above cylinder #4. The oil lines are AN-8s.
MA-4 10-3678-32 carburetor with 47-862 nozzle reamed to .1065” diameter.
What am I missing here? I’m banging my head against a wall trying to find a smoking gun and even my incremental changes aren’t yielding results.
Rather than piggyback on my detonation thread I figured I’d start over with a new baseline of what I’ve tried so far. Today I flew and tried a 3500’ 2400 RPM lean test I read about in another recent thread about carb nozzle size.
https://apps.savvyaviation.com/beta/shared/flight/6985417/be3f4097-6137-4041-8f38-5053deca4858
You can see the results of that test between 13-15 minutes.
The CHTs at climb out are easy to see in that entire graph. After the lean test I tried a climb to 11,500’ and had to terminate that at about 10,000’ due to oil temperature reaching redline.
What I’ve done so far:
New silicone baffle strips sealed as best I can using a dark hangar with the top cowl on and a borescope to see how it is all sealing up.
Every hole I could find on the baffles sealed with RTV. I used a shop light underneath the engine and hit anything that wasn’t through a fin.
Fiberglass RTV baffle wraps - including checking that I didn’t inadvertently block any fins.
Taping off the gaps between my cowl and the baffles around my Cessna style airbox, at the inlets, and blocking the blast tubes pointed at my magnetos.
Reamed the carb main jet to .1065” and validated float height.
What I haven’t done yet:
Investigate the vernatherm.
Instrument the cowling for pressure differential measurements.
Some basic info for reference:
O-320 with 10:1 pistons
7 row oil cooler mounted on the firewall fed by a 3” SCAT hose tapped from the back baffling wall above cylinder #4. The oil lines are AN-8s.
MA-4 10-3678-32 carburetor with 47-862 nozzle reamed to .1065” diameter.
What am I missing here? I’m banging my head against a wall trying to find a smoking gun and even my incremental changes aren’t yielding results.
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