Very Loud Exhaust "Pops/Explosions" at Idle

[rt71]

My 340 is recently broken in and was running very well until I started it today after it sat for a number of days.  I changed the carburetor from a 750 QFR to an Edelbrock 600 cfm and started it up.  The exhaust on the right side started to randomly emit very loud and alarming "pops" at idle but not with increased rpm.  Back to idle they started in again.  There are no apparent vacuum leaks, timing is set at 18* advanced and plug wires are tight.  Any ideas out there?  Help!

[JS29]

Get rid of the Edelbrock and put the Quick fuel back on!!! 

[DeathProofCuda]

Is your intake configured so that the right side of the carb feeds only the right engine bank (i.e., divider in place between the right and left side of the intake) or is the total fuel/air charge shared between both sides?

If I understand your original post, the engine only pops at idle, and only from the right side, but doesn't pop at higher rpm, is that correct?  If so, and you have a divided intake, I'd guess that your idle circuit on the right side of the carb is running too lean.

[rt71]

Put the Quick Fuel back on.  Same result.

[headejm]

Do you consider the "pops" to be backfires? If so, it's more than likely valve train, ignition, or timing related. Do the "pops" cause any flames to shoot out of the carburetor?

A backfire means combustion is happening not when you want it to happen or not where you want it to happen. Some potential causes of backfires:

Plug wires on wrong cylinder
Burnt valve(s)
Timing way off
Misfiring cylinder(s)

[rt71]

The simplest solution is usually the one that works.  Switching 6 and 8 plug wires was it.  Runs like a champ that way. Duh!  Quite embarrassing, but I'm happy.  Thanks to all.

[anlauto]

That would do it...