We have a 9A made in 2003. We bought it in 2017. It has always had CHTs in the low 400 range on first take off at our 4600 ft airport. We added a Surefly mag replacing the right mag last year. Now, instead of CHTs in the 400-410 range, we are getting CHTs in the 415 - 430 range.
I know part of that rise is the Surefly mag that has a hotter and longer spark and at WOT has the spark timing advanced. The CHTs seem to come down into the 370 - 390 range after we pull back the throttle and/or after the vernatherm lets the oil into the oil cooler. The vernatherm seems to open at about 180 - 185 F. We are getting the higher CHTs at 60 F ambient temps. In summer, it's worse.
I plan to replace the 20 year old baffling around the engine and can see on the inside of the upper cowling the dirt marks where air is escaping.
Is there a lower temperature vernatherm that would allow oil through the cooler at a lower temperature? Or is there an adjustable one? I only see one for Lycoming engines online.
I discussed going to a different jet on the MS MA4-SPA 10-5217 carb which maxes out at 12 - 13 gallons/hour. My A&P thinks if I go to the next larger size jet (actually a rebuilt carb) I could get 13.5 to 15 gallons/hour at WOT and use the extra gas for cooling.
I've read most of the discussions here, including the ones that advise to modify the metal baffling to force air over fins that may be starved for cooling air now.
Any advice on what to do first?
I know part of that rise is the Surefly mag that has a hotter and longer spark and at WOT has the spark timing advanced. The CHTs seem to come down into the 370 - 390 range after we pull back the throttle and/or after the vernatherm lets the oil into the oil cooler. The vernatherm seems to open at about 180 - 185 F. We are getting the higher CHTs at 60 F ambient temps. In summer, it's worse.
I plan to replace the 20 year old baffling around the engine and can see on the inside of the upper cowling the dirt marks where air is escaping.
Is there a lower temperature vernatherm that would allow oil through the cooler at a lower temperature? Or is there an adjustable one? I only see one for Lycoming engines online.
I discussed going to a different jet on the MS MA4-SPA 10-5217 carb which maxes out at 12 - 13 gallons/hour. My A&P thinks if I go to the next larger size jet (actually a rebuilt carb) I could get 13.5 to 15 gallons/hour at WOT and use the extra gas for cooling.
I've read most of the discussions here, including the ones that advise to modify the metal baffling to force air over fins that may be starved for cooling air now.
Any advice on what to do first?