rapping-popping from exhaust

billfish

billfish

Senior Member
gradually over the past 6 months my 51 8ba with dual exhaust has been rapping and popping from the exhaust. This only happens when backing down in second or third gear and can get pretty loud. The car has Cherry Bomb glasspacks but did not make this noise for the first three years. Could they just be wearing out or is this a timing or fuel mixture problem, otherwise the car runs great.
 
Bill my car did that the day I installed the glass pack, since changing to the overdrive transmission it doesn't do it nearly as much.
 
On an International truck with dual glasspacks I used to notice exhaust explosions on deceleration sometimes. Putting in a new set of ignition points seemed to make it go away.
 
Usually most use glass packs to get the sound from the start. A nice crackle deceleration.
 
retarded ignition will cause heat, and deceleration backfires. you got lotsa heat on the manifolds?
 
Also, check the plugs to see if you are running too rich. Unburned gas in the exhaust can cause exhaust popping. Maybe the float is starting to go, and letting the fuel level get too high.
 
A bunch of us young ones used to hang around a Porter Muffler shop in town. One of his selling features was steel packs would last much longer than glass packs. He said that the glass would break down and blow out. It took much longer to get the sound from a steel pack as they had to "carbon up" for some time.
 
Did a tuneup this morning-new plugs (Auto Lite 216) new dist cap, cleaned points and rotor, checked dwell (27degrees) checked idle adj (550rpm) with vacuum gauge at 21 and steady. checked timing (on mark) and did a compression check- all cylinders at or near 95 lbs.

Took it out for a spin and got it up to temperature, popping and loud rapping seem to be gone replaced by a nice mellow rumble.

Will try to attach picture of plug-they all looked about the same.
 

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billfish said:
Did a tuneup this morning-new plugs (Auto Lite 216) new dist cap, cleaned points and rotor, checked dwell (27degrees) checked idle adj (550rpm) with vacuum gauge at 21 and steady. checked timing (on mark) and did a compression check- all cylinders at or near 95 lbs.

Took it out for a spin and got it up to temperature, popping and loud rapping seem to be gone replaced by a nice mellow rumble.

Will try to attach picture of plug-they all looked about the same.
Click to expand...

Good to hear. Easy fix. Figured it was likely ignitiion related just like my International. That spark plug looks pretty good.
 
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