exhaust backfire

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Ma Mopar

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Simple is Good
 
Heck we even have simple One Wire
Mopar Points Distributors around for this very type of diagnostics.

Distributor wire to (-) negative side of the coil and one hot wire to the (+) positive side of the coil, ready to test.

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Jbarker said:
Rus

Rusty-I love this! A little good-natured ball busting really makes me feel like I belong. Seriously, I am really impressed by the enthusiasm of this group. I apologize that my posts have been brief and infrequent over the last several days. I have been working way too much but hope to make some progress this weekend.
I fired up the car 2 days ago for the first time this year. Problem persists, but it was backfiring out the driver side!!!???
Did I hallucinate that it was the passenger side all last summer? The backfires were much less frequent though. Maybe 1 every 5 minutes or so. I think because it was cold out? So it was tough to say if it was ONLY the driver’s side. So now I am not worried about that slight header leak.
Another thing (and this is an important detail I forgot to mention to you.). It always is worse when the car is idling low. If I have my foot on the gas and keep it at 11 or 1200 RPMs, it backfires less. With the car in gear and the rpm dipping between six and 800, it backfires more. My brilliant buddy asked if maybe my voltage is dropping, and the ignition box can’t do it’s job if the voltage gets too low. I think he may be on to something. Alternator looks ancient. Maybe at idle the alternator just can’t get it done...? I thank you all again for your knowledge, patience, and humor. I will be looking into this tomorrow. This is a great group!!!
-Jay
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Good cause that's how I meant it. Good natured. Too many sissies on this forum take stuff like the wrong way and get their britches waded up and hide under the kitchen table. lol This is an automotive forum, not a Hello Kitty forum. We're real dudes here, not some 80s metrosexuals. LMAO. You fit right in.....you'll find whatever this is.

I'm too lazy to go back and see.....what carburetor is it again? It could be that the carburetor just needs to be richened up a hair. I'm never on board with any experts of gurus when they part with what's always been the tried and true method for determining pops through the exhaust and that's a lean mixture. Somehow, some way, that's dang near almost without exception what it is. Remember, when engines are cold, they need a richer mixture until they get some heat built up. That's the whole purpose of the choke. If you're right on the ragged edge of being too lean across the board, you can get what you have. That's why I recommend fattening it up some just to SEE what you end up with. If nothing else, it will confirm or eliminate that as a possibility.
 
George Jets said:
Heck we even have simple One Wire
Mopar Points Distributors around for this very type of diagnostics.

Distributor wire to (-) negative side of the coil and one hot wire to the (+) positive side of the coil, ready to test.

View attachment 1715717416

View attachment 1715717417
Click to expand...

You know what my problem would be? And it's really not a problem. If that fixed this issue on my car, and yes, you know what I'm fixin to say already......I'd leave the points in it. LMAO
 
George Jets said:
People are chasing this back to an ignition problem.

Here is a cure !

View attachment 1715717398

Simple is Good
Click to expand...

I know, right? I see MSD this, Pertronix that, Skip White junk (I have one on my truck, LOL) but there's nothing wrong with the Mopar way as long as you stay away from crappy parts and that's not hard to do if you're careful. lol
 
Ceedawg said:
Has anyone mentioned wires cross firing? Chrysler put out a service bulletin describing how to route and shield the wires on my 360 engine because of an idle misfire. Turn out the lights and you’ll see the sparks if any.
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You just caint beat old school and that right therre is as old school as it gets. I love this idea too. I mean really, how QUICK a diagnostic tool is the dark, yet some people either laugh at it or never think of it. So simple.
 
George Jets said:
See you have the Red MSD Box for the ignition, they are known to give trouble.

Drag race buddy is saying the MSD boxes are a racing item are finicky and give trouble. If you want a good running driver go back to the Mopar Factory Ignition, less headaches.

See if you can set up a mopar brain box ignition and test that on there, your problem will probably go away.

View attachment 1715717395

View attachment 1715717396
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The OP said it is a Mallory ignition box, not an MSD. I’m betting it’s fat at idle or it has a bad exhaust valve.
 
yellow rose said:
The OP said it is a Mallory ignition box, not an MSD. I’m betting it’s fat at idle or it has a bad exhaust valve.
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Wasn't this the thread where he did a leak down test and it passed? So much goin on they all run together.
 
LJ67barracuda340 said:
Should we assume the firing order is correct? Ive done that on 5 and 7 before by mistake.
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It's so easy to do I don't care how experienced you are or how many times you've done it right. I normally check that first if I ever have a pop.
 
I believe crossing #5 & #7 will cause immediate backfiring.
Crossing #6 & #8 will give you a surprising good running engine, except under load .
 
getting back to induction cross-fire;
>If a cylinder fires another still on the power-stroke, that's no big deal.
>But if it fires one on the exhaust stroke, with headers that's no big deal, unless there is enough unburned fuel still in that exhaust, and enough oxygen to support further combustion. A leaky header flange would be the hot ticket for the introduction of fresh air to support that, which is why, oh so long ago, I inquired about "induction cross-fire.
>But if a cylinder fires another still on the intake stroke ................. that can't be good,lol.
 
RustyRatRod said:
Good cause that's how I meant it. Good natured. Too many sissies on this forum take stuff like the wrong way and get their britches waded up and hide under the kitchen table. lol This is an automotive forum, not a Hello Kitty forum. We're real dudes here, not some 80s metrosexuals. LMAO. You fit right in.....you'll find whatever this is.

I'm too lazy to go back and see.....what carburetor is it again? It could be that the carburetor just needs to be richened up a hair. I'm never on board with any experts of gurus when they part with what's always been the tried and true method for determining pops through the exhaust and that's a lean mixture. Somehow, some way, that's dang near almost without exception what it is. Remember, when engines are cold, they need a richer mixture until they get some heat built up. That's the whole purpose of the choke. If you're right on the ragged edge of being too lean across the board, you can get what you have. That's why I recommend fattening it up some just to SEE what you end up with. If nothing else, it will confirm or eliminate that as a possibility.
Click to expand...
“We’re real dudes, not 80’s metrosexuals”
Too funny man!
Anyways, carb is Edelbrock 800 thunder AVS. It had a holley 850 hp on it that I switched out in my troubleshooting. But that did not fix the problem. I think carb is unlikely to be the cause.
 
Jbarker said:
“We’re real dudes, not 80’s metrosexuals”
Too funny man!
Anyways, carb is Edelbrock 800 thunder AVS. It had a holley 850 hp on it that I switched out in my troubleshooting. But that did not fix the problem. I think carb is unlikely to be the cause.
Click to expand...

Ok, I tend to agree there. An 800 anything is rich enough to avoid a lean pop when cold so I don't suspect that anymore. Are you 100% sure on the firing order?
 
George Jets said:
See you have the Red MSD Box for the ignition, they are known to give trouble.

Drag race buddy is saying the MSD boxes are a racing item are finicky and give trouble. If you want a good running driver go back to the Mopar Factory Ignition, less headaches.

See if you can set up a mopar brain box ignition and test that on there, your problem will probably go away.

View attachment 1715717395
Click to expand...

that's not an msd ign box.
i have an msd streetfire on my truck and it idles fine. i have an old MSD 6al on another car, it idles fine..
 
I dropped a used engine in my chebby and inadvertently crossed 5&7. It popped.
Buddy did the same thing, 2&4 on another chebby. It would pop every few seconds. And he was adamant he didnt cross wires.
 
yellow rose said:
Are you going to post some pictures of your plugs? Putting a points distributor in there won’t fix anything IMO.
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Probably not, but it might eliminate some things. It's better than doing nothing, right?
 
RustyRatRod said:
Probably not, but it might eliminate some things. It's better than doing nothing, right?
Click to expand...
I am first going to check voltage at idle. If normal, then I will try again to see if backfire is confined to only one side or if it is both sides. I don’t want to exaggerate, but I have had the plugs in and out roughly 240,000 times in the last 8 months. They are a little dark, but not oily. No signs of detonation. If I get stuck I may post some pictures. A week ago, what I really needed were ideas. You gave them to me in spades. Now, what I really need is a day off to work on this thing. I will let you know what I find.
 
Jbarker said:
I am first going to check voltage at idle. If normal, then I will try again to see if backfire is confined to only one side or if it is both sides. I don’t want to exaggerate, but I have had the plugs in and out roughly 240,000 times in the last 8 months. They are a little dark, but not oily. No signs of detonation. If I get stuck I may post some pictures. A week ago, what I really needed were ideas. You gave them to me in spades. Now, what I really need is a day off to work on this thing. I will let you know what I find.
Click to expand...

Don't forget the look in the dark thing either. You can pick up on bad wires or a cracked plug real quick.
 
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