Backfiring

My engine (o-360A1A) ussually backfires through the intake when I pull the throttle abruptly to idle. I have adjusted the idle mixture so as to minimize it but it isn't eliminated. I have also checked for leaks in the induction system. I have primer lines to the #1 and #2 cylinders and even though there is no indication of a leak I am wondering if they could somehow be the cause. Also, I tapped off of #3 cylinder for both the manifold pressure (MP) indicator and the MP input for the LASAR controller. I'm wondering if that could have something to do with it. The engine performs fine other than this. Starts easily, develops full power smoothly, and leans normally during cruise. All the way back at idle there is ussually this low popping like 1 or 2 of the cylinders is not producing power. It stops immediately when I bring the throttle forward. I have the standard carb. Has anyone seen this kind of thing before?

Have you checked the timing of both ignitions??

I have checked and verified the ignition timing.

Popping Sound

You are not alone out there.....

My 0-360 A1A with cs prop (Slick left, Plasma LL right) does exactly the same thing. It's usually during landing approach when I pull back to almost idle. I get some soft popping till just before I land...then it's gone.
Others on the field with similar engines (some with both Slicks) do the same thing. have spoken with them and they have no luck getting rid of it. On the other hand many have over 750 engine-run hours with no apparent problems, so I'm not really worried.
I had the same set up in my previous RV, but no such noises...go figure.

If someone has any solid answers......

Thanks.

The popping that you are hearing is probably in the exhaust. Most RV's pop on approach. The unburnt fuel collects in the exhaust system and then pops.

If you've got a vetterman exhaust (or another very good exhaust), then this is VERY common and has been for decades. Well known phenomenon that is a sign of a well scavenged exhaust on an RV. It's been like that for a very long time!

Don't worry about it and welcome to the RV machine gun approach!

Cheers,
Stein

Backfire

It is not likely your timing. I fly formaiton with team RV most weekends. I have a 360 FP on my 7A. I hear this popping often. I asked Mahlon at TCM.
His comments were not to worry it happens on RV's with big motors and abrupt throttle changes such as in formation flying.
Tad "Stripes" Sargent

Thanks for the replies. I really appreciate it....Jacksel

Besides

You can almost get yourself in the local paper around here for doing that.

I try to NOT pop on aproach in deference to my non aviation neighbours, but it will pop like mad if you haul in on the black knob.

Frank

won't leaving just a tad bit of power eliminate the backfiring?

rv8ch said:

won't leaving just a tad bit of power eliminate the backfiring?

Click to expand...

It does for me.

A little power will keep the popping under control

It does. And that's how I always try to operate.

popping

Mine does too, but we are in good company. You ever heard a P 51 land?