Timing?

[bandkiller]

Is it normal to get a little bit of flame out of the exhaust pipes on an aircraft engine? It only does it at around 1/4 to 3/8 throttle and then after that it picks up and has no problems. The motor is an a-65 continental. Thanks for any help.

 

[duckluv26]

i don't think its normal but its common....lmao!!!

 

[cowboy]

I hear ya Duckluv! Good one.

Bandkiller,
If the timing is too far retarded, it could cause some flame outta the exhaust.

It could be tired or hanging exhaust valves, or a loose valve seat also.
It could be a rich mixture at the lower rpm, and unburned fuel escaping your cylinders.

Are you seeing it on one bank of cylinders, or both?

 

[Des Moines Boater]

No, that is not normal. It sounds like you're running rich on the low speed idle jet. Once you get over 1000 rpm you are running the main jet which could be why you see no problem at higher rpm.

I would first complete a compression check and then adjust the low speed mixture.

 

[Waterthunder]

This is common with A/C motors all you are seeing is unburnt fuel being ignited by hot exhaust gases this usually means your motor is too rich. Which is how most people run airboat aircraft motors because aircraft motors need the extra fuel to run rich and cool the cylinders because they are air-cooled. You are fine! Now if you were lean you would have major problems so if you are seeing a flame out both banks you are a little rich that's all. Now if it's on cylinder then you have a weak hole that ain't properly burning it's charge.

 

[Mike Thurman]

As Waterthunder said, They all blow fire. That is what I like so much about running straight pipes or open headers. The fire and the POP they make. Mufflers ruined all that fun. Does it do it on both sides or one? I see alot of guys that may blow fire on one side or one pipe. A bad exhaust gasket will make a good cylinder blow more fire because it will suck oxygen in. If all cylinders are the same then you are probably fine.

 

[Whitebear]

As Waterthunder said, They all blow fire. That is what I like so much about running straight pipes or open headers. The fire and the POP they make. Mufflers ruined all that fun.

Ain't it the truth Mike ! Nothing better than out camping and watching and listening to be boats with 6" stacks and the blue flames licking from every pipe as they come by! Now THAT is what airboating SHOULD BE !

Long ago when we were much fewer in numbers, I remember sitting in town late night and hearing the drone of an airboat out on the river or marsh and listening close. Ya could figure out who it probably was, where he was running and come pretty close figgerin out what he was doin.........

Scotty