Moparts

backfire only out drivers side exhuast

Posted By: 72d100

backfire only out drivers side exhuast - 10/05/12 03:13 AM

Okay guys im at my wits end on this one.
the motor is a
400 with a edelbrock dp4b intake. 1406 carb
the larger summit cam Camshaft, 1-Bolt, Hydraulic Flat Tappet, Advertised Duration 282/292, Lift .465/.488, Mopar,
long tube headers. no clue tube size.
parts store wires and coils. champion plugs. i think
older electronic ignition box. i have no clue where to start looking .any ideas?
Posted By: hp383

Re: backfire only out drivers side exhuast - 10/05/12 03:19 AM

When does it backfire? Any certain speed or RPM?

Maybe one of the lobes went bad on the cam?
Posted By: 72d100

Re: backfire only out drivers side exhuast - 10/05/12 03:23 AM

it was as idle and just a little bit above.
Posted By: Dave440

Re: backfire only out drivers side exhuast - 10/05/12 03:48 AM

Uhhh... misfire? Bad plug? Wire? Cap? One or two wrong (hot) plugs accidentally installed? Carb loading up maybe dripping fuel into intake ports on that side? Usually when I have a backfire on one side its the carb dripping fuel from venturi boosters due to float too high or dirt in needle and seat.
Posted By: bobs66440

Re: backfire only out drivers side exhuast - 10/05/12 03:51 AM

If it's just a minor backfire, like a pop, pop, pop, it could be a header/exhaust leak.
Posted By: 72d100

Re: backfire only out drivers side exhuast - 10/05/12 03:57 AM

it was doing it a lot worse with the holley on it yesterday so I'm thinking maybe an ignition problem.
Posted By: Jim_Lusk

Re: backfire only out drivers side exhuast - 10/05/12 04:14 AM

Make sure #5 and #7 wires are on the correct plugs.....I've never done that to a car, but I did find where somebody else did it...
Posted By: hp383

Re: backfire only out drivers side exhuast - 10/05/12 04:36 AM

Quote:

Make sure #5 and #7 wires are on the correct plugs.....I've never done that to a car, but I did find where somebody else did it...




I have seen it done many, many, times.

Most recently with a friend who had sworn they were correct, and even had double checked.

Of course his problem was a no start issue, and most likely due to the firing order being reversed on the cap As soon as the rotation was corrected, it popped right off.
Posted By: cornet684me

Re: backfire only out drivers side exhuast - 10/05/12 04:41 AM

we just fired up my buddy's challenger, he swore the wires were right, we put it on a lift, took off the driver side from the header, wld go pow after 5seconds, we took down from the lift, i sd lets look again, we had the #5 and #7 crossed.

Posted By: RapidRobert

Re: backfire only out drivers side exhuast - 10/05/12 04:51 AM

Quote:

i have no clue where to start looking .any ideas?


plug, plug wire, bad ECU, vac leak. You're sure the backfire is on the one side only? I'd do a compression test tho to get a baseline to start with
Posted By: bobs66440

Re: backfire only out drivers side exhuast - 10/05/12 11:50 AM

Quote:

we just fired up my buddy's challenger, he swore the wires were right, we put it on a lift, took off the driver side from the header, wld go pow after 5seconds, we took down from the lift, i sd lets look again, we had the #5 and #7 crossed.




When I bought my car, the owner said it had a stubborn backfire through the carb. Been that way for the 5 years he owned it. I think that's one of the reasons he wanted to get rid of it. #4 and #6 were switched...
Posted By: terzmo

Re: backfire only out drivers side exhuast - 10/05/12 12:59 PM

check plug wires for connection and if they are touching/burned on headers or manifolds
Posted By: scratchnfotraction

Re: backfire only out drivers side exhuast - 10/05/12 01:30 PM

what they said. check for vac leaks also.

my 440 backfires out the driver side only.

but mine is an exhast leak at the rear of the driver exhast manifold.

bang all 3 gears at WOT and let all the way off with a snap,then wait a few seconds and bang like a shotgun. then maybe a couple more if I engine break it all the way down form the WOT blast.

I did a drive by of my buddys with it in 2nd and reved up, killed the key pump the throttle,hit the key and made everyone on the carport dive for cover.

sounds like a SHOTGUN BLAST every time.I have blown muffs apart fliping the key to pop it,but the glass packs are holding up for now.

could be the 3x18 echo tips that make the bang loud.
Posted By: 72d100

Re: backfire only out drivers side exhuast - 10/06/12 07:21 PM

guess it could be because i just have headers with purple hornies bolted directly to them.
and i know this is going to sound dumb but the firing order is 1,8,4,3,6,5,7,2 isn't it
Posted By: MoparforLife

Re: backfire only out drivers side exhuast - 10/07/12 01:15 AM

Yep that is right.Check it at both that is right at both ends.It can be right at the cap but switched at the plugs.
Posted By: scratchnfotraction

Re: backfire only out drivers side exhuast - 10/07/12 02:06 AM

remeber dist goes CCW on fire order.

you can always do a comp test to rule out a burnt valve in a cyl also.
Posted By: 72d100

Re: backfire only out drivers side exhuast - 10/07/12 02:25 AM

i did a little diagnostic work today and heres the even numbered plugs

Attached picture 7410095-even.jpg
Posted By: 72d100

Re: backfire only out drivers side exhuast - 10/07/12 02:29 AM

odd

Attached picture 7410100-odd.jpg
Posted By: RapidRobert

Re: backfire only out drivers side exhuast - 10/07/12 02:37 AM

Those plugs are shot. throw in a new set & see if it straightens out. Is that wet oil or dry carbon?
Posted By: 72d100

Re: backfire only out drivers side exhuast - 10/07/12 02:38 AM

So i cleaned the plugs up because they are fairly new. that old Holley just dumped tons of fuel on them. they cleaned up decent enough i put them back in.
Then i checked the cap and rotor which was practically new. i did notice some up in down play in the distributor, not sure if that's normal or not?
It seemed like when i started it it was running really good and not backfiring. I'm going to play with it a little bit more tomorrow and see
Posted By: 72d100

Re: backfire only out drivers side exhuast - 10/07/12 02:42 AM

Quote:

Those plugs are shot. throw in a new set & see if it straightens out. Is that wet oil or dry carbon?


it was a mix of each. they cleaned up okay so i reused them. im going to put new ones in once i get my first check
Posted By: RapidRobert

Re: backfire only out drivers side exhuast - 10/07/12 02:53 AM

Quote:

i did notice some up in down play in the distributor, not sure if that's normal or not?



Most have alot of lower shaft axial play which is too much. Can drive out the roll pin, slide off the plastic collar and add 1/2" ID shims/washers to reduce it to .005" If using washers check/slightly bevel the sharp edged side on them.
Posted By: 72d100

Re: backfire only out drivers side exhuast - 10/07/12 03:09 AM

if you guys can bear my ugliness i did get a video of it running. what do you guys think? youtube
Posted By: Wagonmaster

Re: backfire only out drivers side exhuast - 10/07/12 04:44 PM

I'm probably going to get flamed for this, but, IMHO, get rid of the Champions. I've run Autolite copper plugs in my MOPARS since my first one, back in 1969. No issues with them, ever.

For your application, plug number 85. $1.60 at your friendly Autozone.
Posted By: Dan Halen

Re: backfire only out drivers side exhuast - 10/07/12 04:53 PM

I've used 85s for over 25 yrs, but that carb looks to be

fouling the plugs..fix that first. May be float level or rich

idle mixture.
Posted By: Rapid340

Re: backfire only out drivers side exhuast - 10/07/12 06:55 PM

plugs look badly oil fouled, take a close look at intake manifold sealing. You could take the carb off and you may be able to detect oil in the plenum.
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