What would you do with this?
 

My throttle produces severely offset CHTs and EGTs at about a 75% position. If I dump in full throttle or pull back to 65% or less all the numbers even out nicely though. I've verified I can get a good EGT rise at altitude by leaning. But this spot around 75% has some wicked offsets. Aerosprort was of little help.

I'd lean the engine out. 11.7 GPH on an O320 is a ton of fuel at 72% power on an O320. It's enough to support almost 170 HP, and you're producing about 115.

Does it clean up when you drop to 10-ish GPH, which is much more in line with a ROP mixture at that power?

What do your fuel flows look like at WOT and 65% power?

--Ian
Dynon Avionics

I will have to lean it out and check to respond to your question but I think it has more to do with the butterfly valve setting. I can check fuel flow at wot and 65% power but that will pry mean climbing to 12500 da or so?

I think I'm realizing some significant ram air horsepower or some significant horsepower increase from the ASA vacuum valve because whereas I only get 2150 rpm static at 1500 msl, I can still wind it up to 2750 at 10,000 DA.

sump riser insert
 

do you have a sump riser insert? lycoming SB-258.

Extremely old SB and it looks like he has a Superior 320. Lean for the altitude and report back, that's a lot of fuel burn. :)

Agree with the leaning recommendation
 

I have likely the same engine in a 9A - Superior IO-320 - furnished by Aerosport Power. At that altitude and at 72% power I'd be leaned w-a-y back and burning 6.5gph or less. Even at <4000 ft running 75% and 100 ROP my fuel burn is ~ 9 to 9.3gph. That 11.7 - as others have observed - is WAY high.

RPM 2690
 

I take it that you have a fixed pitch propeller. A sweet spot at nearly 2700 RPM?
If you had a constant speed prop, you could set around 23/23, lean to around 6-7 GPH and watch things quiet down and cool off.

Here is a photo and my sump riser (spacer) that was asked about previously. Perhaps it should be above the throttle bracket?

Yes... and mounted inside the bottom of the sump. You have a Superior Engine, not going to be your issue. :)

Reiley - can you clarify your response? are you saying the brown spacer should be above the white throttle bracket?