Popping back in exhaust

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mopar head said:
If all else fails, See if your reluctor pin is still in:clock:
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green1 said:
Just throwing this out there. I once bought a 400 T/A 400, that did the same thing. Machinest said it was carbon built up behind the valves, He was right.
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Now these are 2 things I would not have thought of. My Magnum pops alot, not as bad. Even worse on deceleration.
 
My 440 starts popping when one of the plug wires gets burnt from my headers. New plug wire and the problem goes away.

You might want to check each spark plug to ensure they are all good. It doesn't happen very often, but a new part is not necessarily a good part.

Rod
 
This is true. I was called over by a bunch of freinds saying Ya gotta see this. The plug wire was bad OOTB and bleeding electricty over the plug onto the head.

A very cool light show it is.
 
Cudafever: The previous cam was a Crane HV272 .454/.480 lift It also had a Edelbrock LD4B intake manifold on it. The motor dosen't pop up high. Only at idle. Once the motor starts warming up it will pop without me giving it gas, and it will do it out both sides of the motor.
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Is it possible that the carbon from the valve is causing a sticking of the exh valve do to carbon on the valve stem, travailing farther into the guide?


I'm not to sure with the carbon idea as it "should" have a miss at idle and bang at a idle. How Ever, running the eng at a Hi idle and pouring some ATF down the carb(water for the epa friendly guys LOL) should dissolve the carbon.

still thing "compression check" is your first step.
 
The popping on the Pontiac was on decell. Clean carbon out? Rev it and pour Coke in it, or water; old timers trick. The cool pops the carbon off the metal, as contraction is different.
 
we have been having problems with the gas lately in the model As making them pop we used some sea- foam and super and it all went away
 
Check the distributor shaft/ gear. Had a buddy with a GTX did the same thing. The dist. was not moving together with the gear screwing up the timing. Slapped in a new MSD dist. problem solved.
 
Did the car do this before? Is this why you changed the cam?

If not I'm going with vacuum leak on, especially since you stated it smooths out on higher rpm. Check the intake with WD40/starting fluid along both sides see if it smooths the idle. Can't imagine dist, valves or carb if it didn't do it before a simple R&R of those parts.
 
I do not think that the case and the cam etc... change out was an upgrade for performance.
 
If I had to guess, I'd say the cam has little or no vacuum because the "10.5:1" 340 is less than that, and because of that, the power valve is not staying closed. It's way over-rich at idle and the mixture screws won't change that if this is the case. Before you tear into the engine I'd get a $5 vacuum gage and see what level of vacuum you are pulling at idle out of gear, and then in gear, at running temperature. Or, get a 3.5 power valve and stick it in the carb as a test.
 
Thanks for all the help so far guys. I am going to try a few things today when I get off work. I will keep you guys posted.
 
Also, dont forget the DP carbs usually have two power valves. One primary, one secondary. Both need to be rated 1.5-2" less than the idle vacuum or idle in gear for automatics.
 
OK so I found the problem. I feel really stupid about it. My #2 and #4 plug wires was crossed over. I don't know how I missed this everytime I looked over the firing order but I did. I am glad it was that and nothing major though. Thankyou guy's for all of your help and knowledge.
 
Great, good to hear you got it fixed. It's a good example of why it's good to slow down and retrace your steps. Most of the time you can troubleshoot and fix the problem by looking at the things (items) you've touched.
 
Thanks for posting the solution. All to often we don't hear the fix. Very glad that you were able to track it down.
C
 
Well since the motor is running right. I figured that I would let you guys hear it. Again thanks for all of you guys help.

 
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