What causes an exhaust pop in the exhaust system when deceleration.
When lifting on full throttle deceleration You will get a loud explosion in the mufflers.
What causes this ?
Rich side or header leak ?

leak

I have Hedman slip tube headers on my Dart and had that going on a few years back. I had one joint that was real sloppy, so I eliminated that joint and the popping quit.

I've had it bubble and pop in the headers on decel from being too rich

Did it just start after no changes in your combo? Do you have a roller cam? If so, the dist bronze gear might be worn. Mine had never popped and then all of a sudden with no other changes it started. Turns out it was the gear.

Un burnt fuel in exhaust normally.

popping started after installing a 2 inch carb spacer .
Does not do it all the time ! just happened about three times .
Cam is a hyd. roller .
distributor is a new mopar performance electronic item .
I do have a couple minor header exhaust leaks .... could be that .......

could it be the transfer slots on the carb are exposed to much ? would this allow fuel to drop after deceleration? off throttle.

header and or a exhaust leak.

It's an intake leak. When you close your throttle plates at high rpm it draws in more air through where it's leaking without a fuel mixture. It doesn't have enough A/F mixture to ignite until after it gets to the pipes.

Exh leak. It is doing the same thing and air injection pump would do. The extra air it pulls in on decell from the exh is igniting the unburnt gasses in the exh. The air injection pump for emission controls basically does the same thing but they are dumped on decell so thats why cars with them dont do it. Ron

That makes Phill right. It's a leak.

Mine does the same thing- always a leak. My header bolts loosen up after a while. If i catch it in time i can just snug them up with out replacing the gaskets.

header gasket leak

But the popping started after installing a 2" carb spacer. That's where I would look for the leak.

I talked to my local speedshop here and they told me it is in the fuel distribution .
It is on the rich side.......
said to take a 1 or 2 jet sizes out the secondaries.
over abundance of fuel when lifting on the gas pedal.....
Makes sense to me ..... You need Fuel + air + heat to have it explode in the exhaust system Right ?
how can a header or intake leak cause it to pull fuel out of the carb when lifting ? it needs that extra fuel to feed the explosion.
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As I had said it just like an emission air pump which injects AIR into the exh to ignite any unburned fuel and cut down on emission's. Not everything burns in the cyl on ign so if any air is pulled into the exh on decell it can ignite the unburned fuel sorta like what a diesel does. Now of course if the car runs to rich it can make it worse but if there is no air pulled or pumped into the exh then it can be way rich and still wont pop on decell if the car runs an exh system and not open headers. It could have had a small leak that was not enough to cause a poping but if you change the mixture then that small leak may be enough to cause the poping on decell. And you also slam the throttle shut on decell which cuts off the air going into the eng on decell. There are other things that may cause the poping in the exh on decell but 99% of the time it is an exh leak. Ron