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Popping through the carb problem. #1401706 03/13/13 12:49 AM 03/13/13 12:49 AM
Joined: Dec 2003 Posts: 36,840 South San Francisco, Californi... MidPenMopar OP Looking for fun? Keep looking
MidPenMopar OP Looking for fun? Keep looking Joined: Dec 2003 Posts: 36,840 South San Francisco, Californi...	I just started am having a problem with the roadrunners 383 backfiring through the carburetor almost all the time. The only way not to have it do that is to keep the engine above at least 2500 RPM. So just trying to drive down the street I sound like a popcorn machine. The carburetor is a 650 Edelbrock Thunder series and probably only has a thousand miles on it or so. I am running a Petornix igniter and just installed new Accell plugs and new Accell ceramic tipped wires just in case it was arcing through the wires and misfiring. The thing is it wont backfire unless under a low RPM load (like running the engine in say at 2000 RPMs or so in overdrive) . I checked with my timing light and the timing chain seems not to be slipping. If I keep the RPM's up it wont backfire, like say manually shifting from 1st to 2nd, to 3rd to 4th and it wont backfire no matter what I do unless under a load so I am stumped as what to look for next? Could this be a issue with the transmission not in sync with the Throttle Position Sensor maybe? One note is it used to do this exact same thing when the engine was not up to full operating temperature, but once it hit 180 degrees that popping would go away. Now it acts like this even at full warm up. Any thoughts on why this may be happening all of a sudden?? Stu

Re: Popping through the carb problem. [Re: MidPenMopar] #1401707 03/13/13 01:14 AM 03/13/13 01:14 AM
Joined: Feb 2003 Posts: 4,808 Castlegar, BC, Canada That AMC Guy master
That AMC Guy master Joined: Feb 2003 Posts: 4,808 Castlegar, BC, Canada	I'd pull a valve cover just to be sure. Just recently had this happen to a friends' Chivvy 350..... what had happened was a pushrod broke through the rocker and the exhaust valve on one cylinder was now no longer working! Bloody Mary, Full of Vodka, Blessed art thou among cocktails....

Re: Popping through the carb problem. [Re: That AMC Guy] #1401708 03/13/13 01:58 AM 03/13/13 01:58 AM
Joined: Jul 2011 Posts: 960 Chicago PurpleBeeper super stock
PurpleBeeper super stock Joined: Jul 2011 Posts: 960 Chicago	If it were a Holley, I'd say "power valve"... but it's not a Holley. A pop out of the carburetor sounds like an intake valve is not sealed all the way and the fuel in that cylinder is igniting back up through the carburetor. A bent intake valve, bent pushrod or funky rocker all could do that, or even a weak valve spring or burnt valve seat. Maybe run a compression test & see if one cylinder is really low compared to the others? 70 Roadrunner convt. street car 440+6, NOS, 4-spd, SS springs '96 Mustang GT convt. street car '04 4.6 SOHC, NOS, auto, lowered "Officer, that button is for short on-ramps"

Re: Popping through the carb problem. [Re: PurpleBeeper] #1401709 03/13/13 03:38 AM 03/13/13 03:38 AM
Joined: Feb 2010 Posts: 18,493 Granite Bay CA Kern Dog Striving for excellence
Kern Dog Striving for excellence Joined: Feb 2010 Posts: 18,493 Granite Bay CA	The basics of combustion are that the intake tract flows into the motor and the exhaust flows out. When a popping sound is heard coming up and into the intake system, there is a problem somewhere in the cam or valvetrain. A failing camshaft can cause this. If an exhaust lobe is going flat, the only other path for the exhaust to escape is back up through the intake valve. This will result in a popping sound. A burned intake valve or seat can also cause this. Once again, it is the exhaust gases finding another path to escape. A compression test will identify the offending cylinder or cylinders. Pulling the valve covers and run the engine. Look for any rocker arm that appears to move less than the others. If the pushrod at that rocker is loose, you have either a defective lifter, a failed cam lobe or both. With all of the problems lately with the low Zinc levels in todays oils, Camshaft failures are much more common.

Re: Popping through the carb problem. [Re: Kern Dog] #1401710 03/13/13 09:09 AM 03/13/13 09:09 AM
Joined: Dec 2003 Posts: 36,840 South San Francisco, Californi... MidPenMopar OP Looking for fun? Keep looking
MidPenMopar OP Looking for fun? Keep looking Joined: Dec 2003 Posts: 36,840 South San Francisco, Californi...	Thanks people for the advice on where to start looking.

Re: Popping through the carb problem. [Re: MidPenMopar] #1401711 03/13/13 09:10 AM 03/13/13 09:10 AM
Joined: Feb 2005 Posts: 28,312 Cincinnati, Ohio Challenger 1 Too Many Posts
Challenger 1 Too Many Posts Joined: Feb 2005 Posts: 28,312 Cincinnati, Ohio	Double and triple check that you have the spark plug wires on right, it'll pop if the firing order is wrong.

Re: Popping through the carb problem. [Re: Challenger 1] #1401712 03/13/13 09:15 AM 03/13/13 09:15 AM
Joined: Jan 2004 Posts: 27,347 Today? Who Knows? 1_WILD_RT Management Trainee
1_WILD_RT Management Trainee Joined: Jan 2004 Posts: 27,347 Today? Who Knows?	Quote: Double and triple check that you have the spark plug wires on right, it'll pop if the firing order is wrong. This... 18436572 8 7 6 5 4 3 2 1 front of car "The Armies of our ancestors were lucky, in that they were not trailed by a second army of pencil pushers."

Re: Popping through the carb problem. [Re: 1_WILD_RT] #1401713 03/13/13 10:28 AM 03/13/13 10:28 AM
Joined: Dec 2003 Posts: 36,840 South San Francisco, Californi... MidPenMopar OP Looking for fun? Keep looking
MidPenMopar OP Looking for fun? Keep looking Joined: Dec 2003 Posts: 36,840 South San Francisco, Californi...	Yep that was my first thought when it started happening as a couple of the old wires had burned through near the headers. So i figured that was the cause and put on those new ones with the ceramic plug ends. Still the same. If it was a miswired situation it would have that problem all the time, not just under a low RPM load like it does now. If i manually shift the automatic transmission through the gears and hold the revvs above say 2500RPMs it runs fine and no backfiring. The issue only comes when i am on the road and the engine is turning low RPMS. You can staticly revv the engine to redine without any issues at all.

Re: Popping through the carb problem. [Re: MidPenMopar] #1401714 03/13/13 10:47 AM 03/13/13 10:47 AM
Joined: Oct 2011 Posts: 516 ND D dodgedon mopar
dodgedon mopar D Joined: Oct 2011 Posts: 516 ND	I'm going to say its too lean. The same as when its not up to temp. I have had this problem with Eddy carbs before. More so on trucks... When under load they pop back. You can have the same effect when the choke is off and the engine has not completely warmed up. Lean pop... 67 Charger 383 auto 75 Dodge CNT 800 CAT Diesel 2012 Ram Crew cab 5.7 4x4

Re: Popping through the carb problem. [Re: MidPenMopar] #1401715 03/13/13 11:09 AM 03/13/13 11:09 AM
Joined: Aug 2005 Posts: 11,543 chicagoland,usa B buildanother I Live Here
buildanother I Live Here B Joined: Aug 2005 Posts: 11,543 chicagoland,usa	Is this that original survivor 383? If so, I'd pop the valve covers off, crank it over to verify no bad cam lobes.

Re: Popping through the carb problem. [Re: dodgedon] #1401716 03/13/13 11:25 AM 03/13/13 11:25 AM
Joined: Dec 2003 Posts: 36,840 South San Francisco, Californi... MidPenMopar OP Looking for fun? Keep looking
MidPenMopar OP Looking for fun? Keep looking Joined: Dec 2003 Posts: 36,840 South San Francisco, Californi...	Quote: I'm going to say its too lean. The same as when its not up to temp. I have had this problem with Eddy carbs before. More so on trucks... When under load they pop back. You can have the same effect when the choke is off and the engine has not completely warmed up. Lean pop... Im thinking that my be the issue as it seems to make the most sense. Since nothing was changed inside the carb though how could this happen??

Re: Popping through the carb problem. [Re: MidPenMopar] #1401717 03/13/13 11:36 AM 03/13/13 11:36 AM
Joined: Nov 2003 Posts: 36,041 Lincoln Nebraska R RapidRobert Circle Track
RapidRobert Circle Track R Joined: Nov 2003 Posts: 36,041 Lincoln Nebraska	Quote: Since nothing was changed inside the carb though how could this happen?? Intake vac leak/PCV malfunction/brake booster vac leak/A/C vac line leak. EDIT might check reluctor gap/rotor phasing. Holler how things go. MORE EDIT I wonder if the Pertronix is acting up . I've had regular ECU's act like a popcorn machine when they went bad Last edited by RapidRobert; 03/13/13 12:20 PM. live every 24 hour block of time like it's your last day on earth

Re: Popping through the carb problem. [Re: Kern Dog] #1401718 03/13/13 01:16 PM 03/13/13 01:16 PM
Joined: Aug 2006 Posts: 2,535 God's Country Maryland GODSCOUNTRY340 master
GODSCOUNTRY340 master Joined: Aug 2006 Posts: 2,535 God's Country Maryland	Quote: The basics of combustion are that the intake tract flows into the motor and the exhaust flows out. When a popping sound is heard coming up and into the intake system, there is a problem somewhere in the cam or valvetrain. A failing camshaft can cause this. If an exhaust lobe is going flat, the only other path for the exhaust to escape is back up through the intake valve. This will result in a popping sound. A burned intake valve or seat can also cause this. Once again, it is the exhaust gases finding another path to escape. A compression test will identify the offending cylinder or cylinders. Pulling the valve covers and run the engine. Look for any rocker arm that appears to move less than the others. If the pushrod at that rocker is loose, you have either a defective lifter, a failed cam lobe or both. With all of the problems lately with the low Zinc levels in todays oils, Camshaft failures are much more common. Exhaust lobe wore off cam. I love the smell of Deer guts in the morning, it smells like... VICTORY!

Re: Popping through the carb problem. [Re: RapidRobert] #1401719 03/13/13 01:18 PM 03/13/13 01:18 PM
Joined: Jan 2003 Posts: 32,979 Grand Prairie,Texas stumpy I Win
stumpy I Win Joined: Jan 2003 Posts: 32,979 Grand Prairie,Texas	Check the inside of the distributor cap for carbon tracks. I have seen that happen before.

Re: Popping through the carb problem. [Re: stumpy] #1401720 03/13/13 07:32 PM 03/13/13 07:32 PM
Joined: Dec 2003 Posts: 36,840 South San Francisco, Californi... MidPenMopar OP Looking for fun? Keep looking
MidPenMopar OP Looking for fun? Keep looking Joined: Dec 2003 Posts: 36,840 South San Francisco, Californi...	Quote: Check the inside of the distributor cap for carbon tracks. I have seen that happen before. Just checked and the distrubiter cap and it looks good. Things i did before this problem happended. I took my TTI headers and sent them out to be recoated and then reinstlaled them as well as putting in those Accell shorty header plugs.

Re: Popping through the carb problem. [Re: MidPenMopar] #1401721 03/13/13 07:38 PM 03/13/13 07:38 PM
Joined: Feb 2005 Posts: 28,312 Cincinnati, Ohio Challenger 1 Too Many Posts
Challenger 1 Too Many Posts Joined: Feb 2005 Posts: 28,312 Cincinnati, Ohio	Quote: Quote: Check the inside of the distributor cap for carbon tracks. I have seen that happen before. Just checked and the distrubiter cap and it looks good. Things i did before this problem happended. I took my TTI headers and sent them out to be recoated and then reinstlaled them as well as putting in those Accell shorty header plugs. Can't use that accel plug, it don't have enough reach. The plug it's self is not any shorter where it count's for header clearance. Last edited by Challenger 1; 03/13/13 07:44 PM.

Re: Popping through the carb problem. [Re: Challenger 1] #1401722 03/13/13 07:40 PM 03/13/13 07:40 PM
Joined: Dec 2003 Posts: 36,840 South San Francisco, Californi... MidPenMopar OP Looking for fun? Keep looking
MidPenMopar OP Looking for fun? Keep looking Joined: Dec 2003 Posts: 36,840 South San Francisco, Californi...	Quote: [ Can't use that accel plug, it don't have enough reach. Well they are working, but you think that be the issue?? Plugs are cheap so what do you all like to run?? These ACCEL C-Cut performance spark plugs produce a larger spark for more power at high rpms. They improve throttle response and fuel economy and reduce fouling. Their purified Alumina insulator prevents arcing, and their machine-rolled threads protect heads. 7624868-acc-0437s-4.jpg (296 downloads) Last edited by MidPenMopar; 03/13/13 07:43 PM.

Re: Popping through the carb problem. [Re: MidPenMopar] #1401723 03/13/13 07:48 PM 03/13/13 07:48 PM
Joined: Feb 2005 Posts: 28,312 Cincinnati, Ohio Challenger 1 Too Many Posts
Challenger 1 Too Many Posts Joined: Feb 2005 Posts: 28,312 Cincinnati, Ohio	Accel probably makes the right plug for your heads, just the one's you showed won't work for long. Plus that short reach will allow your spark plug threads in your heads to get burned up. Get the right accell plug with the correct reach so the tip of the plug is where it belongs.

Re: Popping through the carb problem. [Re: Challenger 1] #1401724 03/13/13 09:20 PM 03/13/13 09:20 PM
Joined: Jun 2005 Posts: 5,112 Western Md. skicker "The Champ"
skicker "The Champ" Joined: Jun 2005 Posts: 5,112 Western Md.	If the plugs you installed were hotter than the ones you removed that will also amplify a lean condition. I hate to mention it but the last time I had this problem it was a cam lobe on an exhaust valve. ...FAFO...

Re: Popping through the carb problem. [Re: MidPenMopar] #1401725 03/13/13 09:24 PM 03/13/13 09:24 PM
Joined: Feb 2005 Posts: 28,312 Cincinnati, Ohio Challenger 1 Too Many Posts
Challenger 1 Too Many Posts Joined: Feb 2005 Posts: 28,312 Cincinnati, Ohio	Stu, is there a reason you took down the picture of the 2 plugs?

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