popping from exhaust on deceleration

[Bill Monk]

First, let me say I appreciate everybody that has taken the time to give advise to me on this site. It has proven to be an invaluable tool to diagnose problems so thanks!

Now to the problem: Engine has a slight hesitation at low throttle but runs like a scalded dog when you step on it. When I take my foot off the throttle, there is a random popping from the exhaust. It isn't a loud bang but a pop pop and is random. It doesn't seem to do it when decelerating from a light load.
I'm pretty sure it is not a vacuum leak and the car has new plugs. One thing I noticed when trying to get it timed in is that the vacuum advance on the distributor does not appear to be working. I have it plugged to manifold vacuum and I saw no change with it plugged off v/s plugged in. I rather doubt that has anything to do with the popping but just throwing that out there. Does this sound like a timing thing or what?

 

[dmartin]

Bill if it is an automatic transmission it is getting to much gas if it is a stick it is your mufflers


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[mac]

what were your instructions to set timing from 4 seconds flat? his setups pull timing out under WOT when manifold vacuum drops off. you may have too much initial timing or may be a little lean. verify your timing settings and go from there. if timing is set to where the instructions tell you, try backing timing off 2 degrees and see if that makes any change.

 

[Bill Monk]

4 speed brother

 

[Bill Monk]

what were your instructions to set timing from 4 seconds flat? his setups pull timing out under WOT when manifold vacuum drops off. you may have too much initial timing or may be a little lean. verify your timing settings and go from there. if timing is set to where the instructions tell you, try backing timing off 2 degrees and see if that makes any change.

My setup from FOB hasn't got here yet. As far as running lean, I'm definitely not running rich (based on plugs) but she idles well where it is. The center carb is out 1 1/2 turns and it doesn't want more than that. I have plenty of get up and go under throttle, even before I kick in the outboards. I know idle isn't a good indicator of what's going on at deceleration but I don't know. I'm leaning toward a distributor problem which is why I ordered the setup from FOB in first place. As it is right now, I get the most vacuum and it idles well at 30 BTDC with no starting issues. I probably should have waited until I installed the new distributor but this stuff drives me crazy. I just can't let it go until I resolve the issue. Mopar OCD!

 

[zupanj]

My first thought is an exhaust leak at the header or manifold.

 

[Bill Monk]

My first thought is an exhaust leak at the header or manifold.

OK, I'll check that as well

 

[Big John]

what were your instructions to set timing from 4 seconds flat? his setups pull timing out under WOT when manifold vacuum drops off. you may have too much initial timing or may be a little lean. verify your timing settings and go from there. if timing is set to where the instructions tell you, try backing timing off 2 degrees and see if that makes any change.

X2

Usually, popping through the exhaust on deceleration is a lean condition. I'd look at that and timing. It may be a combination of the two.

 

[mac]

what carb are you running?

 

[mac]

My setup from FOB hasn't got here yet. As far as running lean, I'm definitely not running rich (based on plugs) but she idles well where it is. The center carb is out 1 1/2 turns and it doesn't want more than that. I have plenty of get up and go under throttle, even before I kick in the outboards. I know idle isn't a good indicator of what's going on at deceleration but I don't know. I'm leaning toward a distributor problem which is why I ordered the setup from FOB in first place. As it is right now, I get the most vacuum and it idles well at 30 BTDC with no starting issues. I probably should have waited until I installed the new distributor but this stuff drives me crazy. I just can't let it go until I resolve the issue. Mopar OCD!

i would still begin with backing off the intial timing a bit.

 

[Bill Monk]

what carb are you running?

6 bbl

 

[mac]

6 bbl

that is a whole different animal. i would double check all float settings and idle mixture settings on all carbs.