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Popping through the carb problem.
Posted By: MidPenMopar
Popping through the carb problem. - 03/13/13 04:49 AM
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
Posted By: That AMC Guy
Re: Popping through the carb problem. - 03/13/13 05:14 AM
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!
Posted By: PurpleBeeper
Re: Popping through the carb problem. - 03/13/13 05:58 AM
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?
Posted By: Kern Dog
Re: Popping through the carb problem. - 03/13/13 07:38 AM
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.
Posted By: MidPenMopar
Re: Popping through the carb problem. - 03/13/13 01:09 PM
Thanks people for the advice on where to start looking.
Posted By: Challenger 1
Re: Popping through the carb problem. - 03/13/13 01:10 PM
Double and triple check that you have the spark plug wires on right, it'll pop if the firing order is wrong.
Posted By: 1_WILD_RT
Re: Popping through the carb problem. - 03/13/13 01:15 PM
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
Posted By: MidPenMopar
Re: Popping through the carb problem. - 03/13/13 02:28 PM
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.
Posted By: dodgedon
Re: Popping through the carb problem. - 03/13/13 02:47 PM
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...
Posted By: buildanother
Re: Popping through the carb problem. - 03/13/13 03:09 PM
Is this that original survivor 383? If so, I'd pop the valve covers off, crank it over to verify no bad cam lobes.
Posted By: MidPenMopar
Re: Popping through the carb problem. - 03/13/13 03:25 PM
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??
Posted By: RapidRobert
Re: Popping through the carb problem. - 03/13/13 03:36 PM
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
Posted By: GODSCOUNTRY340
Re: Popping through the carb problem. - 03/13/13 05:16 PM
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.
Posted By: stumpy
Re: Popping through the carb problem. - 03/13/13 05:18 PM
Check the inside of the distributor cap for carbon tracks. I have seen that happen before.
Posted By: MidPenMopar
Re: Popping through the carb problem. - 03/13/13 11:32 PM
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.
Posted By: Challenger 1
Re: Popping through the carb problem. - 03/13/13 11:38 PM
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.
Posted By: MidPenMopar
Re: Popping through the carb problem. - 03/13/13 11:40 PM
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.
Posted By: Challenger 1
Re: Popping through the carb problem. - 03/13/13 11:48 PM
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.
Posted By: skicker
Re: Popping through the carb problem. - 03/14/13 01:20 AM
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.
Posted By: Challenger 1
Re: Popping through the carb problem. - 03/14/13 01:24 AM
Stu, is there a reason you took down the picture of the 2 plugs?
Posted By: Dcuda69
Re: Popping through the carb problem. - 03/14/13 01:38 AM
Sure sounds like a cam lobe...really hope it's not!!
BTDT not fun(or cheap) Good luck and let us know what ya find
Posted By: MidPenMopar
Re: Popping through the carb problem. - 03/14/13 01:56 AM
Quote:
Stu, is there a reason you took down the picture of the 2 plugs?
Yes that was just a stock photo and not indicitve of the one's i have.
Here are my plugs as i just pulled them to check the condition so far.
They seem to be fine but then they only have about 100 miles on them all so far.
Posted By: sogtx
Re: Popping through the carb problem. - 03/14/13 02:04 AM
Make sure your nuts/bolts that hold the carb to the manifold are torqued to a min of 150 in lbs .
Not just tight by hand with a ratchet
sometimes the stupidest things ...
did you adjust timing this year , ?
What else did you touch / change . go backwards .
vacuum advance attached or plug fell off the port ?
You just had a little surgery with the header change , something didnt go back together right .
did it do it last year ? ..
recheck your wires , buy some firewires with teh big numbers on them ..
because you just did something , Ill bank on it not being a cam ..
Posted By: B1arno
Re: Popping through the carb problem. - 03/14/13 03:45 AM
Just my two cents but,
If my car was running well and I did a few things to it and it started running like crap, I would look really hard at what I did to make sure it was right and possibly start reversing things to see if it cleared up.
Arno
Posted By: MidPenMopar
Re: Popping through the carb problem. - 03/14/13 04:13 AM
Quote:
Just my two cents but,
If my car was running well and I did a few things to it and it started running like crap, I would look really hard at what I did to make sure it was right and possibly start reversing things to see if it cleared up.
Arno
You know it's not running bad it runs just fine except for that popping at low RPMs. That's why it hard to diagnose, im going to try new plugs first and see if that helps??
Posted By: rss
Re: Popping through the carb problem. - 03/14/13 04:25 AM
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...
I'd be looking for an intake/vacuum leak and then start going through the carb.
Posted By: B1arno
Re: Popping through the carb problem. - 03/14/13 04:47 AM
Quote:
Quote:
Just my two cents but,
If my car was running well and I did a few things to it and it started running like crap, I would look really hard at what I did to make sure it was right and possibly start reversing things to see if it cleared up.
Arno
You know it's not running bad it runs just fine except for that popping at low RPMs. That's why it hard to diagnose, im going to try new plugs first and see if that helps??
Thats what I would do. Change back one at a time what you can to see if that makes the difference.
Posted By: Kern Dog
Re: Popping through the carb problem. - 03/14/13 06:00 AM
Sorta unrelated but here goes:
Last year I installed a Gear Vendors overdrive unit. To get it to fit, I had to cut out the exhaust crossover pipe. The engine sits in the car a bit out of level, so I tried to clock it after loosening the motor mount nuts. I laid a 2 foot level across the valve covers, but I had to spin the distributor a few degrees because the vacuum can was in the way....After the GV was in, I drove to the exhaust/muffler shop. The car ran terrible and was really slow turning over. It pinged & detonated even at light throttle. I pulled over about a mile after leaving and clocked the distributor until the car ran like before. That wasn't all though. I had also removed the valve cover breather. I noticed a CLANG then saw a chrome ball rolling behind me as I was rolling at about 50 mph. (What the heck was tha..... Oh, I know what it was)
The point is, it was good advice from the guy who suggested to try looking at the changes you made.
Posted By: Challenger 1
Re: Popping through the carb problem. - 03/14/13 11:54 AM
Are you sure those are the correct style plugs for your heads, they look awfully short to me? My 440 heads take a long reach plug.
Then use just a drop or two of motor oil on the the threads, no anti seize, imo. Good luck to you!
Posted By: 1_WILD_RT
Re: Popping through the carb problem. - 03/14/13 01:00 PM
Quote:
Are you sure those are the correct style plugs for your heads, they look awfully short to me? My 440 heads take a long reach plug.
Then use just a drop or two of motor oil on the the threads, no anti seize, imo. Good luck to you!
Stock heads like Stu runs take short reach plugs, Edelbrock's take long reach plugs.. Small blocks take long reach... For Stu's car those look Ok but I'd still screw in a set of NGK's just to see were it puts him..
Posted By: Challenger 1
Re: Popping through the carb problem. - 03/14/13 01:28 PM
Quote:
Quote:
Are you sure those are the correct style plugs for your heads, they look awfully short to me? My 440 heads take a long reach plug.
Then use just a drop or two of motor oil on the the threads, no anti seize, imo. Good luck to you!
Stock heads like Stu runs take short reach plugs, Edelbrock's take long reach plugs.. Small blocks take long reach... For Stu's car those look Ok but I'd still screw in a set of NGK's just to see were it puts him..
Thanks
Posted By: Triggerfish
Re: Popping through the carb problem. - 03/14/13 02:14 PM
The 70 383 Mag in my Power Wagon did the same thing. Eddy 600 AFB, larger, high 400's cam & not much torque to get the beast rolling.
I added a 1" four hole phenolic spacer & that helped the carb signal, but it would still pop off idle at a light if I wasn't careful. Leak down test revealed two dead cylinders & my hands would get wet with fuel when I held them over the tail pipes. I suspected a blown head gasket between cylinders, but when disassembled to install new heads & smaller cam, turns out the orig heads did not have hardened seats & the exhaust valves were sunk into the head so far, they weren't sealing at all, allowing the intake charge to go right out the exhaust & causing a lean condition. New heads with hardened seats, smaller torque cam & viola, no more popping thrut he carb. The other guys like Randy, who're a lot more mechanic savy than me, might chime in about burnt valves causing the popping.
Posted By: MidPenMopar
Re: Popping through the carb problem. - 03/14/13 02:27 PM
I will get a new set of regular plugs and see what happens when i install them without the anti sieze on the theads. Maybe these shortie plugs are to blame for the problem??
Personally i think it's an issue with fuel loading up in the carb due to the transmission getting into overdrive too quickly. I say this as if i shift manually and stay out of overdrive untill over 2500 RPM the problem does not happen.
I can stand on it and let the transmission shift automaticly and no popping issue all the way to redline....
Posted By: therocks
Re: Popping through the carb problem. - 03/14/13 06:23 PM
Try a set of NGK plugs.they are cheap and work.I run them in my aluminum headed 440 with 12.5 domes on the street.I also dont care for Accel wires.I run Taylors on everything.Mine with 2 inch TTIS have been on at least 12 years.My kids 413 with 2 1/8 tubes have been on 5 years with no problems.He runs my old worked 516s with NGK plugs.You migh also have a valve thats just barely burnt.Compression test would tell.Also to check timing chain.Turn crank to zero.Then while someone watches manually turn it back till the dist moves moves.I like to see less than 10 degrees on an old chain.Rocky
Posted By: GODSCOUNTRY340
Re: Popping through the carb problem. - 03/14/13 07:52 PM
A burnt valve wouldn't cause popping through the carb. You'd have a dead cylinder and/or popping out the exhaust with a burnt valve. Exhaust valves are the ones that get burnt. I've NEVER seen a burnt intake valve.
Posted By: Paul_Fancsali
Re: Popping through the carb problem. - 03/14/13 08:36 PM
Replace the accel plugs J-12Y or RJ12-Y the accell are too cold period
Posted By: Triggerfish
Re: Popping through the carb problem. - 03/14/13 10:14 PM
You're right & it was popping thru the carb, but that must've
been because of a lean condition. The cam was way to big for
the truck & I read in the Eddy manual that big cams can cause a lean
condition off idle? It only backfired thru the tail pipe a couple of
times when first starting up.
Posted By: MidPenMopar
Re: Popping through the carb problem. - 03/14/13 11:35 PM
Quote:
Replace the accel plugs J-12Y or RJ12-Y the accell are too cold period
I just got a set of Ac Delco R435 plugs to try this time.
Posted By: 500ciDuster
Re: Popping through the carb problem. - 03/16/13 12:46 AM
I had A 360 and it did that because it rounded a cam lobe off
Posted By: MidPenMopar
Re: Popping through the carb problem. - 03/16/13 01:37 AM
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?
Posted By: RapidRobert
Re: Popping through the carb problem. - 03/16/13 01:59 AM
Quote:
I will take a test run tomorrow
I can hardly wait
Posted By: MidPenMopar
Re: Popping through the carb problem. - 03/16/13 03:16 AM
Quote:
Quote:
I will take a test run tomorrow
I can hardly wait
You and me both 
Posted By: 70Cuda383
Re: Popping through the carb problem. - 03/18/13 03:19 PM
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?
Posted By: Challenger 1
Re: Popping through the carb problem. - 03/18/13 04:00 PM
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. 
Posted By: 70Cuda383
Re: Popping through the carb problem. - 03/18/13 05:26 PM
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.
Posted By: Challenger 1
Re: Popping through the carb problem. - 03/18/13 05:36 PM
I just knew that back fire out of the pipes on decell was a vacuum leak. My brakes were working fine too, but I did have a very small erratic idle that was just starting at the same time it backfired coming down that big ole mountain, made me notice it sooner.
First thing I did was plug the vacuum tap at the manifold and go drive it. No more more backfire and idle was better. So I knew it was external of the motor while in Vegas. Drove it carefully without power brakes.
We stayed at Circus Circus in there campground. The paper work said no working on RVs or cars at the campground sites. So I couldn't do much plus it was 115 degrees and my car is black. Thanks to AC it was not bad in it. Took like a 1/2 hour to cool down and I let it idle with the AC cranking a few times because it was so hot out.
Posted By: MidPenMopar
Re: Popping through the carb problem. - 03/19/13 04:20 AM
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??
Posted By: RapidRobert
Re: Popping through the carb problem. - 03/19/13 04:30 AM
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
Posted By: MidPenMopar
Re: Popping through the carb problem. - 03/19/13 02:32 PM
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??
Posted By: Challenger 1
Re: Popping through the carb problem. - 03/19/13 03:22 PM
Have you pulled the valve covers yet? I'm hoping it's not the cam?
Posted By: Joesixpack
Re: Popping through the carb problem. - 03/19/13 04:57 PM
pull valve covers and inspect valve springs, do compression test on 8 cyl.make sure advance in distributor is working.
Posted By: skicker
Re: Popping through the carb problem. - 03/19/13 05:39 PM
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.
Posted By: RapidRobert
Re: Popping through the carb problem. - 03/19/13 08:53 PM
Quote:
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?
the simple answer is that more load puts more demand on the ign system & if it's going bad then even normal ign requirements cross that line & make it misfire. I certainly would not suggest buying new parts & guessing but if you have another dist/ECU in your stash I'd toss it in for a test as we're running out of ideas for what's going on so we might have to start swapping some parts. I would check rotor phasing & rotor tip to cap terminal clearance. Keep us updated
Posted By: 70Cuda383
Re: Popping through the carb problem. - 03/19/13 09:13 PM
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.
Posted By: Dcuda69
Re: Popping through the carb problem. - 03/19/13 09:40 PM
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!
Posted By: MidPenMopar
Re: Popping through the carb problem. - 03/20/13 12:16 AM
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??
Posted By: sogtx
Re: Popping through the carb problem. - 03/20/13 12:36 AM
Unplug vac advance , brake booster ?
Did you check your carb bolts ?
How do you know youre not lean ?
You can spray starting fluid around base gaskets
And manifold and if your idle rises
You might have a leak .
Whose coil ? I guess it could be bad ...
Id hate to think u have a worn lobe
Posted By: MidPenMopar
Re: Popping through the carb problem. - 03/20/13 12:54 AM
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?
Posted By: sogtx
Re: Popping through the carb problem. - 03/20/13 02:22 AM
Coils do go bad , but in my experience at hi rpms
Posted By: screamindriver
Re: Popping through the carb problem. - 03/20/13 02:44 AM
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...
Posted By: mickm
Re: Popping through the carb problem. - 03/20/13 04:11 AM
stu, look at it this way. if it IS the cam, then you get to decide on ahhh... how spirited you want your engine to be after this!
Posted By: MidPenMopar
Re: Popping through the carb problem. - 03/20/13 05:05 AM
Quote:
stu, look at it this way. if it IS the cam, then you get to decide on ahhh... how spirited you want your engine to be after this!
Mick, I am planning to rebuild the engine at the end of this year and will probably go back to less aggressive cam profile than what is in there now. I'm more interested in driveabilty than power so i can finally start going places without worry if something major is going to snap on me 1000 miles from home.
I just got the brakes and electrial systems all dialed in now the last thing is the engine itself.
Posted By: GTX MATT
Re: Popping through the carb problem. - 03/20/13 05:49 AM
Pop through the carb under a load usually indicates a lean condition to me
Posted By: ek3
Re: Popping through the carb problem. - 03/20/13 06:38 AM
pop from carb means there is ignition with the intake valve open. that would most commonly be ignition [ malfunction] at the wrong time, or, ignition is at the correct time but the intake valve is open at the wrong time. bad valve spring,bent or broken parts keeping valve open.....either way it is a timing issue
Posted By: Kern Dog
Re: Popping through the carb problem. - 03/20/13 06:50 AM
Its a good thing that there is a consensus on this.
Nothing is more frustrating than getting 214 different opinions.
Posted By: 70Cuda383
Re: Popping through the carb problem. - 03/20/13 01:00 PM
Quote:
pop from carb means there is ignition with the intake valve open. that would most commonly be ignition [ malfunction] at the wrong time, or, ignition is at the correct time but the intake valve is open at the wrong time. bad valve spring,bent or broken parts keeping valve open.....either way it is a timing issue
could be, but again...not always! I've experienced it twice, and neither time was it timing related. it was a bad/weak coil the first time, and a lean condition from a vacuum leak the second time. cam, timing chain, distributor timing were all fine.
Posted By: bigblock340power
Re: Popping through the carb problem. - 03/20/13 01:59 PM
Hi Stu. Lots of good advice here. But with all this advice, it seems your chasing your tail, "fixing" without a definite direction. Problem is, your car is at your house, not here. Go to where you can do these tests on the engine, with someone good at this sort of thing. I just got done going through something like this too. But I finally just went through all the tests, and found the problem, fixed it. This sounds like an older motor you've got. Take the valve covers off, pull the plugs, spine the motor. Do a look-see at the valve train. Do the comp. test, a leak down, and test the spring pressure (look for broken springs, and bent push rods). This will rule out a few things, or point you in the right direction. I know I'm just covering some of the same things others have told you, but you need to do these things!
Take a look at these you tubes, just a base line for ya.
Mike
PS, one other thing, put that monster on a scope, see what's up with the spark.
http://www.youtube.com/watch?v=M92CGjpiMs4http://www.youtube.com/watch?v=nJ7RXu4nxkc
Posted By: ek3
Re: Popping through the carb problem. - 03/21/13 02:46 AM
Quote:
Quote:
pop from carb means there is ignition with the intake valve open. that would most commonly be ignition [ malfunction] at the wrong time, or, ignition is at the correct time but the intake valve is open at the wrong time. bad valve spring,bent or broken parts keeping valve open.....either way it is a timing issue
could be, but again...not always! I've experienced it twice, and neither time was it timing related. it was a bad/weak coil the first time, and a lean condition from a vacuum leak the second time. cam, timing chain, distributor timing were all fine.
any time you get combustion in the intake and out the carb, you have a timing issue.[meaning a bad coil firing at the wrong time will do it].yes it is a bad coil but it is firing at the wrong time. a backfire through the carb can not happen unless the intake valve is open.i only say this to help the thinking process of what [when] it is actually happining.
Posted By: Keith Black®
Re: Popping through the carb problem. - 03/22/13 10:45 PM
I'd say an exhaust lifter is on its way out. Engine speed / oil pressure pumps it up but it is more or less collapsed otherwise.
Let us know how you fix it !
Posted By: MidPenMopar
Re: Popping through the carb problem. - 03/23/13 05:17 AM
Quote:
I'd say an exhaust lifter is on its way out. Engine speed / oil pressure pumps it up but it is more or less collapsed otherwise.
Let us know how you fix it !
Got a new coil today via Summit and we shall see what happens but i think it's a lean issue in the carb after reading all the responces on here and the MML.
Posted By: RapidRobert
Re: Popping through the carb problem. - 03/23/13 06:17 AM
Stu
pleeese solve this
Posted By: MidPenMopar
Re: Popping through the carb problem. - 03/23/13 03:43 PM
Quote:
Stu pleeese solve this
Hey Robert I'm trying to do my best but due to the weather (I dont have a garage to work in) my unrelenting work schedule and now getting sick i am left with little time to work on the car when the weather is nice outside. If the new coil does not fix it, i will work on getting the car to a shop asap.
Sorry this got so out of hand i just wanted a few ideas of what to look for and i got some good advice so thank you to all who have helped out.
Stu
Posted By: bennydodge
Re: Popping through the carb problem. - 03/23/13 05:55 PM
sounds like the cam.. I wouldn't spend another dime on parts.
Buddy of mine had the same problem last year with his 440-6 charger. The center carb sounded like a popcorn machine, turned out to be three flat lobes on the cam. Pull the valve covers and roll the engine manually to verify...or pull the intake, they're sooooooo easy on a big block.
Posted By: RapidRobert
Re: Popping through the carb problem. - 03/23/13 06:02 PM
Quote:
Sorry this got so out of hand
Stu
Hey bro it's all good 
& if I was closer I'd help you for free which I never do 
Posted By: MidPenMopar
Re: Popping through the carb problem. - 03/23/13 06:24 PM
Quote:
sounds like the cam.. I wouldn't spend another dime on parts.
Buddy of mine had the same problem last year with his 440-6 charger. The center carb sounded like a popcorn machine, turned out to be three flat lobes on the cam. Pull the valve covers and roll the engine manually to verify...or pull the intake, they're sooooooo easy on a big block.
So i did some carb tuning research in my spare time and what i found out since the engine clears up fine after about 2500 RPM when it moves to a more richer circut it would apper that like a lot of others said it's a LEAN issue and not an ignition issue as i first thought.
So i guess that the next step is to try swapping another similar carb out and see if that fixes the problem. That is my plan for next week.
Posted By: scatpacktom
Re: Popping through the carb problem. - 03/23/13 06:36 PM
Quote:
A burnt valve wouldn't cause popping through the carb. You'd have a dead cylinder and/or popping out the exhaust with a burnt valve. Exhaust valves are the ones that get burnt. I've NEVER seen a burnt intake valve.
I have. Made a rhythmic popping noise out of the carb. Didn't stop me from driving home from the shore though.
All this talk about spark plugs and carbs... I would do a compression test and a leak down test right away.
Posted By: Kern Dog
Re: Popping through the carb problem. - 03/23/13 08:03 PM
Quote:
.... the next step is to try swapping another similar carb out and see if that fixes the problem. That is my plan for next week. [/quote
Seriously, there isn't anyone near STU that can offer up a carburetor to test for him? I'm 2 hours away and I have PLENTY of functional carbs. Let me know STU. 600? 750? 850? Thermoquads? I even have a few Carter AVS 4 barrels.
Posted By: MidPenMopar
Re: Popping through the carb problem. - 03/23/13 09:50 PM
Quote:
Seriously, there isn't anyone near STU that can offer up a carburetor to test for him? I'm 2 hours away and I have PLENTY of functional carbs. Let me know STU. 600? 750? 850? Thermoquads? I even have a few Carter AVS 4 barrels.
I had two nice used Edlebrock 600's that i took off over the years and of course i loaned them all to friends (for just a few days) who never gave them back. You have to see the irony there...
No biggie i am going to work on mine first and see once i take it apart if the jets are messed up somehow.
Posted By: B1arno
Re: Popping through the carb problem. - 03/24/13 12:22 AM
Stu,
I've got a new 650 Thunder series we can swap on and give it a test.
Posted By: meepmeep70
Re: Popping through the carb problem. - 03/24/13 01:28 PM
Quote:
Stu,
I've got a new 650 Thunder series we can swap on and give it a test.
i've got an 800 thunder series edelbrock Stu if your needing to test i'll send your way
Posted By: MidPenMopar
Re: Popping through the carb problem. - 03/24/13 05:15 PM
Ok so yesterday i got some time to finally work on the car.
#1 I installed a new epoxy filled Flamethrower coil.
#2 I took out the air screws and cleaned them. blew out the opening in the carb and reinstalled to factory one and a half turns.
Then cleaned the inside and exterior of the carb with spray cleaner.
#3 Switched the distrubter vacume hose from the left side of the carb to the right just for kicks.
#4 Replaced the FRAM oval air grabber filter with a stock paper filter.
One thing i noticed was my indash tach started reading correctly again. I know this as for a long time it read about 500RPM high. Now it is exactly on the money with my new Sun tach i just installed.
I drove it all over last night and it still popped slighty only now when in 4th gear on the freeway under 2000 RPM but it's 75% better i would say. When i drove it on the surface streets it had no more issues at all as i would not stay in the lower RPM range for any legenth of time.
So i'm pretty happy things are almost cleared up. I think the next thing is to take the carb apart and look at the main jets for any issues.
Thanks for all the good ideas and advice.
Posted By: RJS
Re: Popping through the carb problem. - 03/24/13 07:45 PM
Try this very easy trick.
Get the car running with airfilter off, rev up engine and choke it while revving with the choke or your hand (It may hurt your hand alittle if your doing it right).
Me and my buddy used to call this giving the carb a BLOWJOB, it has cured many driving issues than any other trick out there.
It causes an extreme vacuum in the carb and if anything is lodged it will free the dirt out.
Posted By: 1_WILD_RT
Re: Popping through the carb problem. - 03/24/13 07:50 PM
Quote:
Try this very easy trick.
Get the car running with airfilter off, rev up engine and choke it while revving with the choke or your hand (It may hurt your hand alittle if your doing it right).
Me and my buddy used to call this giving the carb a BLOWJOB, it has cured many driving issues than any other trick out there.
It causes an extreme vacuum in the carb and if anything is lodged it will free the dirt out.
Back before PC world we called that an Italian Tune Up.... 
Posted By: MidPenMopar
Re: Popping through the carb problem. - 03/24/13 07:51 PM
Quote:
Try this very easy trick.
Get the car running with airfilter off, rev up engine and choke it while revving with the choke or your hand (It may hurt your hand alittle if your doing it right).
Me and my buddy used to call this giving the carb a BLOWJOB, it has cured many driving issues than any other trick out there.
It causes an extreme vacuum in the carb and if anything is lodged it will free the dirt out.
Well that's easy and cheap so i will try it!! 
Posted By: RapidRobert
Re: Popping through the carb problem. - 03/24/13 07:52 PM
Quote:
So i'm pretty happy things are almost cleared up.
Progress! If it's a carterbrock I'd also take out the clusters & spray them good & just me I'd sub the old coil back in for a quick test just to confirm or deny that it was strickly an A/F ratio issue.
Posted By: RJS
Re: Popping through the carb problem. - 03/24/13 11:16 PM
Quote:
Quote:
Try this very easy trick.
Get the car running with airfilter off, rev up engine and choke it while revving with the choke or your hand (It may hurt your hand alittle if your doing it right).
Me and my buddy used to call this giving the carb a BLOWJOB, it has cured many driving issues than any other trick out there.
It causes an extreme vacuum in the carb and if anything is lodged it will free the dirt out.
Back before PC world we called that an Italian Tune Up....
You wanna hear how I shower in 30 seconds too????
Posted By: MidPenMopar
Re: Popping through the carb problem. - 04/15/13 02:32 PM
Just an update as to how things turned out with the popping issues i was having.
I took the roadrunner to my buddies shop and he spent some time tuning the Edelbrock 650 Thunder Carb. After a couple of times replacing jets he told me had to turn down a pair of jets on a lathe to get the perfect size for my application.
The car runs awesome now, better then it ever has before. So in the end it was a very lean condition that was causing all the issues.
Thanks for all the advice and help people.
Stu
Posted By: Challenger 1
Re: Popping through the carb problem. - 04/15/13 02:59 PM
Thanks for the update!!
Posted By: skicker
Re: Popping through the carb problem. - 04/15/13 06:05 PM
Maybe that explains why when I took the Eddy off of mine and put on the 650 Holley the popping only went away after I jetted up the primaries.
I like the Eddy carb but I'm just not as up on tuning them as I am the Holley.
Posted By: Challenger 1
Re: Popping through the carb problem. - 04/15/13 06:50 PM
Quote:
Maybe that explains why when I took the Eddy off of mine and put on the 650 Holley the popping only went away after I jetted up the primaries. I like the Eddy carb but I'm just not as up on tuning them as I am the Holley.
IMO there's a whole bunch of carbs running lean nowadays causing all kinds of problems, like overheating, running poorly, burning off header coatings and more.
10% ethanol needs to jetted up over straight gas, but lot's don't believe it because of some electronic gismo that is not accurate on our old cars and motors.
Edlebrock 1406 carbs are way lean right from the factory, you need to jet those up before even putting it on your motor.
My opinion...
Posted By: Anonymous
Re: Popping through the carb problem. - 04/17/13 12:58 AM
I too, wanted to say lean. Didn't want to get laughed at. One of the biggest clues was your header coatings. The guys said coatings last unless there was something improper done, such as breaking in a new engine and letting it run to hot that the coating would not fail. This would be the result of running lean. You would have very high exhaust temps. This is most likely what caused your header coating to fail, also. Good luck, Stu.
Posted By: RapidRobert
Re: Popping through the carb problem. - 04/17/13 02:04 AM
Quote:
10% ethanol needs to jetted up over straight gas, but lot's don't believe it because of some electronic gismo that is not accurate on our old cars and motors.
What gismo are we speaking of here?
Posted By: Challenger 1
Re: Popping through the carb problem. - 04/17/13 01:38 PM
Quote:
Quote:
10% ethanol needs to jetted up over straight gas, but lot's don't believe it because of some electronic gismo that is not accurate on our old cars and motors.
What gismo are we speaking of here?
I have read quite a few posts where folks are complaining about overheating. I suggest to jet it up to see if it will help cooling. And folks tell me that's not it because they have one of these web page
Well just because it says one thing doesn't mean you shouldn't try to jet it up anyway and see how it runs.
IMO that tool is not a bad tool but I would not let it keep me from tuning my car and see how it does no matter what reads. Plus I think the sensor can get tainted and give false readings. I may be all wrong...
I do know one thing for sure, richer is cooler.
And I think some folks are tuned for the race track and not the street.
Posted By: RapidRobert
Re: Popping through the carb problem. - 04/17/13 02:32 PM
You know that's interssting as I just bought a used LM1 so I could stop guessing where I'm at. thank you for the timely info as I will get it in the recommended range then experimant going a bit richer to see what develops but as is I have no idea if I am way too lean or way too rich. I will call Innovate & ask them if they think it should be sent in to be recalibrated
Posted By: skicker
Re: Popping through the carb problem. - 04/17/13 02:48 PM
I've seen numerous topics referencing high water temperatures and a too rich condition, as if one is the cause of the other. I have always read this and thought somebody must know more then me.
In my experiences more fuel typically reduces water temp.
Posted By: MidPenMopar
Re: Popping through the carb problem. - 05/17/13 05:23 PM
Ok guys the carb issues were all fixed with a the help of a kit with a few differnet metering rods and now the engine runs better than it ever has.
We swapped out the original radiator for a new Champion unit, 195 theromstat, and a new B&M trans cooler.
Thanks for all the advice on this!!
Stu
