I could use some input. I recently rebuilt my Lycoming O-360-A1D (MA-4-5 carb) on my RV-4. About 15 hours into the break-in, all my CHTs have come down nicely except #3 (back right). It’s still consistently 40-60 degrees hotter than the other three.
Here’s the data from a flight I did this morning—run up plus three laps around the pattern.
At low altitude, even at WOT, I have no problem keeping 1, 2, and 4 below 380–either rich or LoP. But #3 keeps wanting to run away. I can climb out at full throttle, but #3 is usually hitting 440 F by the time I hit pattern altitude, so I have to pull back the throttle.
I’ve checked and rechecked, and reworked all my baffles. No air gaps. I’ve even added a spacer to the inter-cylinder baffle so more air can flow throw the short fins on the back.
The right side of the engine is consistently hotter than the left. So maybe fuel distribution needs work? Or maybe I’ve just managed to glaze #3?
Mike Busch has me scared to death of pulling a cylinder and replacing it with the engine on the engine mount. Too much risk of under-stretching the through bolts.
My plan is to keep flying and keep #3 to 440 or less, then monitor oil consumption for another 10-20 hours. But any thoughts would be appreciated.