News:

It appears that the upgrade forces a login and many, many of you have forgotten your passwords and didn't set up any reminders. Contact me directly through helpmelogin@dodgecharger.com and I'll help sort it out.

Main Menu

popping through exhaust

Started by B5charger, July 11, 2011, 10:53:10 AM

Previous topic - Next topic
Print
Go Down Pages1 2 All
User actions

B5charger

July 11, 2011, 10:53:10 AM
What causes the popping sound through the exhaust when I take my foot off the throttle?  Under load there is no problem, only when I take my foot off the throttle at speeds of 30mph +.  Is it a timing problem?

resq302

#1
July 11, 2011, 11:04:49 AM
Could be timing a little off or distributor bushing is wearing causing excessive play.
Brian
1969 Dodge Charger (factory 4 speed, H code 383 engine,  AACA Senior winner, 2008 Concours d'Elegance participant, 2009 Concours d'Elegance award winner)
1970 Challenger Convert. factory #'s matching red inter. w/ white body.  318 car built 9/28/69 (AACA Senior winner)
1969 Plymough GTX convertible - original sheet metal, #'s matching drivetrain, T3 Honey Bronze, 1 of 701 produced, 1 of 362 with 440 4 bbl - auto

B5charger

#2
July 11, 2011, 11:22:28 AM
If the timing is off, should I advance it more or retard it?

resq302

#3
July 11, 2011, 11:34:27 AM
Hopefully Ron could chime in here but I would say it needs to be retarded just a tad bit.  Almost sounds like it is firing late when the exhaust valve is opening causing the backfire through the exhaust.
Brian
1969 Dodge Charger (factory 4 speed, H code 383 engine,  AACA Senior winner, 2008 Concours d'Elegance participant, 2009 Concours d'Elegance award winner)
1970 Challenger Convert. factory #'s matching red inter. w/ white body.  318 car built 9/28/69 (AACA Senior winner)
1969 Plymough GTX convertible - original sheet metal, #'s matching drivetrain, T3 Honey Bronze, 1 of 701 produced, 1 of 362 with 440 4 bbl - auto

B5charger

#4
July 11, 2011, 01:04:37 PM
well I just tried advancing the timing and started to get pinging.  Then I retarted it and the pinging is gone but the popping is still there with the throtlle off at cruising speed.  There's no popping at low speed (in town).  Could it be a leak in the exhaust?

Musicman

#5
July 11, 2011, 04:15:37 PM
Your fuel mix may be a little on the rich side...

nascarxx29

#6
July 11, 2011, 04:56:05 PM
Vacuum leak will cause you to lean out.Also check heat riser operation :Twocents:
1969 R4 Daytona XX29L9B410772
1970 EV2 Superbird RM23UOA174597
1970 FY1 Superbird RM23UOA166242
1970 EV2 Superbird RM23VOA179697
1968 426 Road Runner RM21J8A134509
1970 Coronet RT WS23UOA224126
1970 Daytona Clone XP29GOG178701

oldschool

#7
July 11, 2011, 05:15:00 PM
exhaust leak...
1968 cuda formula S bb 4-sp                          1968 Charger R/T 500" 4-sp
1970 Charger 580" 4-sp
1970 Cuda Convertible 500" 4-sp
1970 Cuda Convertible 500" 4-sp
TOO MUCH HORSEPOWER, IS ALMOST ENOUGH!

maxwellwedge

#8
July 11, 2011, 06:21:29 PM
Bad sealing valves, rings. Do a compression and a vacuum check as well.

B5charger

#9
July 11, 2011, 08:52:11 PM
An exhaust leak I can check (covering the exhaust and listening for a leak elswhere)? But could it be because of too lean or too rich? how can I adjust it either way?  It's a Carter 2BBL.

FLG

#10
July 11, 2011, 10:55:09 PM
Too rich or an exhaust leak will cause the issue, or an exhaust leak by itself could as well.

B5charger

#11
July 12, 2011, 08:55:23 AM
Well I turned out (counter clockwise) on the air/fuel mixture screws at the front of the carb about 3/4 turns.  They are now about 2 1/4 turns open and it seems to have done the trick.  The only question I have now is whether I made the mixture more rich or more lean?

FLG

#13
July 12, 2011, 04:57:19 PM
You sure your backfiring from the exhaust not the carburetor?

B5charger

#14
July 12, 2011, 09:26:13 PM
I'm not sure if it was backfiring.  It was more of a popping sound; not a shotgun bang.  The closest sound I can think of comes from bikes as they let off the throttle.  You hear the same pop,pop,pop etc.  Whatever it was, it's gone now.  So I take it that I richened the mixture a little?

Musicman

#15
July 12, 2011, 09:36:54 PM
Sounds like you were popping out the carb then  :shruggy:

Either way, your good to go now right :2thumbs:

firefighter3931

#16
July 13, 2011, 07:56:49 AM
A popping sound out the exhaust is a lean mixture.  :yesnod:


Ron
68 Charger R/T "Black Pig" Street/Strip bruiser, 70 Charger R/T 440-6bbl Cruiser. Firecore ignition  authorized dealer ; contact me with your needs

440

#17
July 13, 2011, 11:37:34 AM
I thought it's because it gets loaded up with fuel and continues to burn in the exhaust....

Musicman

#18
July 13, 2011, 12:49:27 PM
Quote from: 440 on July 13, 2011, 11:37:34 AM
I thought it's because it gets loaded up with fuel and continues to burn in the exhaust....

I would have to agree... popping exhaust is usually a sign of a rich mix, timing issues, or worn valves.   

FLG

#19
July 13, 2011, 02:42:12 PM
Quote from: firefighter3931 on July 13, 2011, 07:56:49 AM
A popping sound out the exhaust is a lean mixture.  :yesnod:


Ron

Generally any overly rich mixture will flood the exhaust with unburt fuel and cause a backfire.

I usually never disagree with Ron...

Id imagine it would be possible if the idle circuit is very lean it never burns in the chamber and just goes in the exhaust until it collects enough to backfire??  :shruggy: :shruggy:

B5charger

#20
July 13, 2011, 08:30:08 PM
Well if Ron says the popping is due to a lean mixture and turning the mixture screws out a little more enriches it.  It did stop the popping, but it does seem to make more sense the other way around.  Can you help explain Ron? :scratchchin:

firefighter3931

#21
July 13, 2011, 10:05:12 PM
Quote from: B5charger on July 13, 2011, 08:30:08 PM
Can you help explain Ron? :scratchchin:


Sure  ;)

The original quote stated :

"What causes the popping sound through the exhaust when I take my foot off the throttle?  Under load there is no problem, only when I take my foot off the throttle at speeds of 30mph +.  Is it a timing problem? "

The problem exists with the throttle blades closed under full load....so it's not a main jet issue. The idle jets & circuit come into play in this scenario so when the idle mixture was fattened up (richer) the "lean pop" was eliminated. Other conditions that will cause this occurance is leaky exhaust where outside air is sucked into the mainfolds creating a lean condition and popping.

Both are lean conditions created through different mechanisms but the results are the same.


Hope that helps....



Ron
68 Charger R/T "Black Pig" Street/Strip bruiser, 70 Charger R/T 440-6bbl Cruiser. Firecore ignition  authorized dealer ; contact me with your needs

Musicman

#22
July 13, 2011, 11:21:35 PM
There's also no air entering the manifold when the throttle plate closes either... When you close the throttle plate a high vacuum is created in the manifold which pulls a rich fuel mix in through the idle circuit. The rich fuel mix does not burn completely in the engine because there is not enough air, but when the exhaust valve opens there is a supply of fresh air and it ignites causing an exhaust backfire (afterfire).
:Twocents:

FLG

#23
July 14, 2011, 12:53:53 AM
Yes but an overly lean condition can cause the mixture to not ignight and pool up in the exhaust as well  :shruggy:

Musicman

#24
July 14, 2011, 08:01:32 AM
Yep that's true, just as Ron said... but usually a Lean mix situation will result in both backfire (intake) and after-fire (exhaust), where as a momentary Rich mix will result in after-fire. Whether or not the vehicle was popping through the carb, or through the exhaust, or both, doesn't really matter at this point... the problem was fixed. This thread has provided some good information for future readers who may have a similar issues however, so all in all  :2thumbs:
Print
Go Up Pages1 2 All
User actions