Author Topic: Misfiring, backfiring....440  (Read 1525 times)

Offline DAYLEY/CHALLENGER

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Misfiring, backfiring....440
« on: October 05, 2016 - 07:32:24 PM »
Ok...Having trouble with a 440 with Edlebrock 750.  Replaced the distributor, rebuilt the carb. Starts good, idles great, cruises at 40 to 45, no issues,BUT try to go more gas pedal, starts skipping, even backfiring some.  Help please.
Dave or David




Offline Cudakiller70

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Re: Misfiring, backfiring....440
« Reply #1 on: October 05, 2016 - 08:20:39 PM »
Fuel filter? or filters if you still have them in the carb fuel inlets.
« Last Edit: October 05, 2016 - 08:23:24 PM by Cudakiller70 »
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Offline DAYLEY/CHALLENGER

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Re: Misfiring, backfiring....440
« Reply #2 on: October 05, 2016 - 08:42:17 PM »
Changed the fuel filter first last week.  Put in two new screens in the needle  seats with the carb rebuild.  I thought  not getting fuel too.
Dave or David

Offline 73440

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Re: Misfiring, backfiring....440
« Reply #3 on: October 05, 2016 - 08:54:53 PM »
Try looking into the carb and see what kind of spray happens when pumping the gas,
Was everything done at the same time?
67 440
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73 Barracuda w/ 68 440
65 Plymouth Fury III , I sold ,was my Nana's car till 92 yo.
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Offline Cudakiller70

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Re: Misfiring, backfiring....440
« Reply #4 on: October 05, 2016 - 09:45:14 PM »
Does it do this only on the road under load?
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Offline 1970 RT Challenger 1970

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Re: Misfiring, backfiring....440
« Reply #5 on: October 05, 2016 - 09:54:05 PM »
I had a bad Pickup Coil on a GM HEI Distributor and 350 V8 that's similar to the symptoms you are having, misfiring, skipping, bucking. It was just ugly and intermittent going down the road at 40 to 60 mph. You could feel the violent vibration through the whole vehicle and drive train of the truck.
« Last Edit: October 05, 2016 - 09:59:58 PM by 1970 RT Challenger 1970 »

Offline DAYLEY/CHALLENGER

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Re: Misfiring, backfiring....440
« Reply #6 on: October 05, 2016 - 10:22:42 PM »
Distributor was done several weeks back and I haven't had but a few chances to,drive the car until now.  Did the fuel filter last week and the carb today.   She used to,run fine and started going down hill over the past few months.  Just have been occupied with family issues and have not had time to work on her very much since Feburary.  I thought about timing but have not checked that yet, also unhooked the vac line to,heater controls and capped the tube on the carb in case it is a vacuum leak.  The only other vac lines is ffor dist and power brake booster.

The carb spray looked good, I adjusted the float levels per instructions, etc.

She will get up,to 40 to 45 easily but not with heavy foot .  .?...?  Mash more and  misfire, skip.
Dave or David

Offline 734406pk

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Re: Misfiring, backfiring....440
« Reply #7 on: October 05, 2016 - 10:52:16 PM »
Ok...Having trouble with a 440 with Edlebrock 750.  Replaced the distributor, rebuilt the carb. Starts good, idles great, cruises at 40 to 45, no issues,BUT try to go more gas pedal, starts skipping, even backfiring some.  Help please.

I would check the secondary ignition circuit i.e. Coil wire, cap, rotor, plug wires and even the spark plugs.  Use an ohm meter on the wires. Your symptoms seem to indicate secondary ignition leakage to ground IMO.
1973 Challenger 440 6 pack auto 3.91 rear
2012 Dodge Ram 3500 dually 6.7 Cummins Fleece EFI Live
1973 Challenger 318 2bbl auto 2.73 rear 22.5 mpg RIP
1970 Challenger TA 340 4bbl auto-Sold and sad
1999 Dodge Ram 3500 dually 5.9 Cummins Fleece tuned VGT-sold
1995 Kawasaki ZX1100E & still alive