exhaust popping sound .. backfiring, back-pressure or popcorn?

[JCN247DE]

If this question has been posted before... I missed it in the search mode.

My -7A has an Aerosport O-360 with 9.2:1 pistons, lightspeed plasma I on the top plugs, slick mag on the bottom plugs and a Hartzell BA prop on the nose. The exhaust is the standard Vetterman's that Van's sells.

When I pull the power back coming into the pattern, the exhaust pops and cackles like an old Harley! Is this normal for the above set-up? Another pilot told me he heard it "backfire" when I shut it down at the fuel pumps the other day. I didn't hear it as I was unlatching the canopy, talking to my passenger, etc.

I've checked mag timing and assume the lightspeed timing curve is correct as it is connected to the MAP pressure tube via the supplied air tube.

Any ideas????

Thanks,

Jeff - 115hrs -7A

[Ironflight]

Jeff,

This thread started yesterday, and has some feedback:

http://www.vansairforce.com/communit...ead.php?t=8363

[JCN247DE]

Thanks Paul....