Backfire and burble trouble.
 

I am having real trouble with my IO-360 engine burbling and making all sorts of testosterone exhaust type noise as I throttle back. I have to make this verrrrry slowly to keep it from making all kinds of noise. What should I be looking for and how do I fix it?

I have been advised that this could be air in the exhaust, so I borrowed a smoke generating exhaust leak detection tool. There is quite a bit if leakage between the short stack and the main crossover pipes. How do I stop this? Should I have the pipes welded or can I tape them up somehow, at least for a test. Welds seem to be a bad idea but may be the answer. Opinions? Thoughts? Help!!!

Are there other places I should also be looking for the source of the problem?

I am having a hard time sneaking the plane in and out of the airport without people calling the fire and police about the airplane that is inevitably gonna crash with engine failure.

Are you talking about something more than the normal exhaust popping noise when the throttle is almost or fully closed?

This has been covered before.Try this link and see if this is what your talking about. If not you have a problem.
Rich
http://www.vansairforce.com/communit...+throttle+back

Hum....
 

Aerosport O-360-B1B, Lightspeed Ignition, Airflow Performance FI, Vetterman Crossover 4-into-2 exhaust.

I never cut to idle quickly. I start several miles out before pattern and just nudge it out or the popcorn machine will kick in. It will pop just on a taxi also unless I give it some throttle to quite it down.

Thanks for the replys. I had bought into the just live with it until my neighbor with the same engine claimed no noise from his plane. Could he be pulling my leg?

I will look into what he is using for an exaust system. I think this popping is excessive for my plane. I can look into mixture at idle also. Could changing the exaust system to another style fix the problem?

This is certainly not the norm for RVs. I have never seen one pop while taxiing and mine doesn't do it (although it does in flight if cutting the throttle quickly). Sounds like you've got something else going on.

TOAD,

I replaced the seals around the intake tubes into the sump and mine stopped popping. I checked everything under the sun to no avail. When I replaced the intake tube seals, it became a different engine. Good luck.

Excessive lean mixture at idle can cause popping on the ground. To check for proper mixture slowly lean the mixture at idle and you should get a 50 to 75 RPM rise just before idle cut off. If you don't I suspect you are running lean and need to enrichen the idle setting. Is this Carb or injected?

Gary Specketer

This is a fuel injected engine
 

This is an injected engine. I am wondering if the AirFlow performance induction system is different from other injection systems or plays into the issue in some way.

Now that I am searching my memory I am convinced that the engine used to run much better and that things are getting worse. I will head out to the hangar as soon as I get home tonight to look into mixture and look for a leak on the induction side. I suspect the exhaust is as tight as it was on day one. All my efforts were directed to exhaust and I will switch to other areas because I do not see anything that looks significant there.

It sounds like you have already checked for leaks around the exhaust, but anywhere it can suck in air (exhaust to cylinder head, exhaust probe, a pin hole in a weld etc) will cause it to pop in the exhaust pipe.

loose bolts
 

Toad,
You might want to check the exhaust and intake bolts where they attach to the cylinders heads. The first couple hundred hours everything loosens up.
I had a blue streak(gas) leaking from the top of #3 intake. The gaskets were shot after 500 hrs.I check mine at annual and some need to be re-torqued.
Hope this helps.
Rich