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Re: Popping through the carb problem.
[Re: 70Cuda383]
#1401749
03/18/13 12:00 PM
03/18/13 12:00 PM
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Joined: Feb 2005
Posts: 28,312
Cincinnati, Ohio
Challenger 1
Too Many Posts
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Too Many Posts
Joined: Feb 2005
Posts: 28,312
Cincinnati, Ohio
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Quote:
Quote:
Put in the new plugs and it fired up nicely and sounds a little better. I will take a test run tomorrow and see if the new plugs did any good? 
Did california fall off into the ocean, and "tomorrow" never came?
did you drive it?
I was going to say that I had popping through the carb on the 383 that was in my car. very similar to what you're describing, only when the engine was under a load.
my problem was that the brake booster blew out, and created a LARGE vacuum leak. 3 of my exhaust valves burned up because that half of the manifold had gone lean.
Hope your plus fix it! if not...am I starting sooner rather than later on overhauling this 383 I have here? 
Dang...how long did you drive it for the valves to burn up?
I had my power brake booster start leaking last summer and had some small back fire on slow down out the back of the exhaust when there was high vacuum. I replaced it but didn't hurt the motor.
Mine started popping out the exhaust coming down Pikes Peak and that's when I noticed it. Drove the car all around Vegas in 115 degree temps for 3 days after that and took it home and replaced the booster. Drove around Vegas with it pinched off so I would not look like a dufus with a back firing 340. Never even dreamed about burning up valves. 
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Re: Popping through the carb problem.
[Re: Challenger 1]
#1401750
03/18/13 01:26 PM
03/18/13 01:26 PM
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Joined: Oct 2003
Posts: 21,345
Marysville, O-H-I-O
70Cuda383
Too Many Posts
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Too Many Posts
Joined: Oct 2003
Posts: 21,345
Marysville, O-H-I-O
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Quote:
Drove around Vegas with it pinched off so I would not look like a dufus with a back firing 340. Never even dreamed about burning up valves.
I dunno. never had any indication that the brake booster was leaking. power brakes were still working great.
I'd guess that the difference between burned exhaust valves and not, is that you identified the leak as the booster immediately and plugged the hose so it wasn't continuing to run lean, where as it took me longer to find the source of the leak. I spent a lot of time messing around with the carb, gaskets, etc. looking for what the source of the popping was before I found it was the leak.
Heck, I even thought that maybe my spark was getting weak since it was not idling funny, still driving fine, and would just backfire occasionally under load. spent some time swapping parts there too, thinking it was from weak spark, before I went on to look for vacuum leaks.
I had no idea how bad things were until it started to really drop off in power. funny thing is, that even running on 5 cylinders, it was still smooth and didn't show signs of missing. it was just much slower than usual. that's when I broke out the compression gauge and found 0 PSI on 3 cylinders.
**Photobucket sucks**
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Re: Popping through the carb problem.
[Re: 70Cuda383]
#1401752
03/19/13 12:20 AM
03/19/13 12:20 AM
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Joined: Dec 2003
Posts: 36,840
South San Francisco, Californi...
MidPenMopar
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OP
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Joined: Dec 2003
Posts: 36,840
South San Francisco, Californi...
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Quote:
Did california fall off into the ocean, and "tomorrow" never came?
did you drive it?
Yep I swapped out the Accell shorty header plugs for some regular AC Delco plugs. I also put on new ceramic covered boot wires that are supposed to handle the heat of the headers but just to be sure I also wrapped them in heat insulting material.
I checked and double checked the firing order and made sure all was good with that. I checked to see if the timing chain is loose (via my timing light) and it seems fine
Then took the car out for a drive and it still pops badly through the carb and now it's even popping though the exhaust as you let off of it, but that may be the side pipes with not enough back pressure.
I took the car out and did some tests by running it up to 5000 RPM and it seemed ok once I got past the popping and stumbling but started missing about 5200 PRM. That just might be valve float or where the Pertonix quits??
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Re: Popping through the carb problem.
[Re: MidPenMopar]
#1401753
03/19/13 12:30 AM
03/19/13 12:30 AM
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Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
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On a tough one I'd start back at the basics with a compression test & a leakdown test. Cap the vac adv which will alter the rotor phasing & see if anything changes for better or worse. Do you have another ign system handy to sub in for a test. EDIT got a points dizzy you could sub for a quick test. I think the Pertronix is acting up
Last edited by RapidRobert; 03/19/13 01:03 AM.
live every 24 hour block of time like it's your last day on earth
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Re: Popping through the carb problem.
[Re: RapidRobert]
#1401754
03/19/13 10:32 AM
03/19/13 10:32 AM
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Joined: Dec 2003
Posts: 36,840
South San Francisco, Californi...
MidPenMopar
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Quote:
I think the Pertronix is acting up
I was thinking that too, but why would it not happen without a load on the engine?
I can run the engine up to redline with not an issue at all in park but once i get moving i have to keep the engine over say 2500 PRMs to not pop through the carb.
I pretty much knew it was not going to change with new plugs and wires, but it was worth a shot.
I think it's not an ignition issue as if it was say the Pertronix module or the coil wouldn't it happen all the time even staticly?? 
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Re: Popping through the carb problem.
[Re: Joesixpack]
#1401757
03/19/13 01:39 PM
03/19/13 01:39 PM
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Joined: Jun 2005
Posts: 5,102
Western Md.
skicker
"The Champ"
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"The Champ"
Joined: Jun 2005
Posts: 5,102
Western Md.
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Mine had an intermitent popping at low RPM's under load. New Eddy carb that was ran one summer with about 2800 mile on it. I threw a new Holley on it. Almost identical pop persisted till I added a little jet to the primaries. It was lean on the primary circuit. I would agree with the cam lobe if it was more consistent. If it was a lobe it would be more likely to do it all the time, not just under load.
Last edited by skicker; 03/19/13 01:41 PM.
...FAFO...
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Re: Popping through the carb problem.
[Re: RapidRobert]
#1401759
03/19/13 05:13 PM
03/19/13 05:13 PM
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Joined: Oct 2003
Posts: 21,345
Marysville, O-H-I-O
70Cuda383
Too Many Posts
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Too Many Posts
Joined: Oct 2003
Posts: 21,345
Marysville, O-H-I-O
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Load on the engine means slow engine speed and lots of throttle opening. The cylinders are getting full charges of air and are under lots of pressure. That pressure needs a strong spark to ignite, and if the system is weak, it's easier to "jump the gap" outside of the cylinder and you get a miss.
I had a coil break down on me when it was hot. Left me stranded. It started by backfiring and popping under load, but would rev fine in neutral. Got so bad the engine finally stalled and wouldn't restart. After it cooled down it ran fine again.
I replaced the coil and it never happened again.
--it was also that experience that caused me to think it was my ignition system again when my booster blow out, and why I kept driving it trying to figure out what was wrong with my ignition, before thinking that maybe it was a vacuum leak instead.
**Photobucket sucks**
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Re: Popping through the carb problem.
[Re: skicker]
#1401760
03/19/13 05:40 PM
03/19/13 05:40 PM
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Joined: Oct 2005
Posts: 4,945
WI
Dcuda69
master
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master
Joined: Oct 2005
Posts: 4,945
WI
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Quote:
I would agree with the cam lobe if it was more consistent. If it was a lobe it would be more likely to do it all the time, not just under load.
Back in the Chev 305/Olds 307/Cad 4100 days I had plenty of them run half way decent till you leaned on them..then they would sound like a popcorn machine Broken/weak valve springs can do the same thing.
I hope I am wrong. A running compression test can help to isolate valve train problems that a cranking test can miss. Good luck Stu!  
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Re: Popping through the carb problem.
[Re: 70Cuda383]
#1401761
03/19/13 08:16 PM
03/19/13 08:16 PM
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Joined: Dec 2003
Posts: 36,840
South San Francisco, Californi...
MidPenMopar
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South San Francisco, Californi...
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Quote:
I replaced the coil and it never happened again.
Ok that was one of my thoughts as well. I had a box of coils i could swap out but as i always do i gave them all away to friends in need.
Is there any way to bench test my existing coil??
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Re: Popping through the carb problem.
[Re: sogtx]
#1401763
03/19/13 08:54 PM
03/19/13 08:54 PM
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Joined: Dec 2003
Posts: 36,840
South San Francisco, Californi...
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Quote:
Whose coil ?
Its a Pertronix 40,000 volt coil and i installed it when i switched over to a new distrubter with the Pertronix ignitor module say maybe 5 years ago. I have yet to see a coil go bad, but i guess there could be a first time?
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Re: Popping through the carb problem.
[Re: sogtx]
#1401765
03/19/13 10:44 PM
03/19/13 10:44 PM
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Joined: Feb 2004
Posts: 7,196
Harrisburg, Pa.
screamindriver
master
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master
Joined: Feb 2004
Posts: 7,196
Harrisburg, Pa.
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Quote:
Coils do go bad , but in my experience at hi rpms
Not always...Had a buddie's go bad last year on a cruise...No issues right up to the point where it started backfiring like a gun blast just motoring along...Extra ECM,ballast resistor,coil, might need a chase vehicle soon with spare parts when our cars start to hit 50 years old... Been in a few cars with wiped lobes, as stated it's usually a more consistant,timed popping...
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