69 383 runs bad

I have a 69 charger 383 124000 original miles it started this miss /hestitation and part throttle , and like a slight bucking at highways speeds , now it has been converted to electronic ignition 20 years ago . I've had it that long , never a problem with the car , so I did plugs, wires, cap , rotor , coil , pickup coil , new carb , checked and rechecked timing , gets way worse when warms up !! Now nothing I did or replaced made the problem go away or get better at all !! Checked for vacuum leaks ( none ) , did compression test all at about 125 ,now while running you hear the miss out of both tailpipes (true duel exhaust ) then I take a dollar Bill while running and it starts flapping and occasionally gets sucked into tailpipe , ( now I can do that to both pipes with same result) now hears where I decided to pull intake and check for valve issue , brought heads to machine shop exhaust seat were bad replaced all and did complete head job on both heads , now the engine was completely rebuilt , new cam lifters , pistons , rings , bearings , bored 30 over , ( completely rebuilt ) put engine in started it , and same thing , sounds like a miss at idle almost like running on 7 cylinders ( rough or shaky when revved )and a really bad miss and skipping sound out both tailpipes way worse when hot !! How can brand new motor do the same thing ?? What am I over looking , like I said coil is new has good spark that I can see , any other things I can do ?? Maybe a bad coil or spark box ?? Please help I was suppose to move last month to another state but this car is now in the shop in ct and I need to get it done so I can leave ,

Just the basics, you checked the vacuum advance, and the actual distributor for run out, etc. The brain boxes seem to either work, or not work.

I had the distributor out to replace the pickup coil it looks fine , how do I check for runout?

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I'm so stumped here almost to the point pulling motor out again and bring to machine shop , but I don't want to get them pissed and say they screwed it up , I'm so out of ideas

When I play with distributor I can grab the rotor and move it left to right a lot , and can move shaft up and down a lot , seems to much to me , any ideas how much play should be in distributor ? Can this cause the issue I have?

Sounds like the dist. may be wore out, a new one isn't much. Mine was doing this and I finally figured this out and now it is fixed. You may need to check where your timing chain is set too. Good Luck with it. Ronnie

Well, to check run out or play, mount a dial indicator against upper part of shaft, spin lower half. Then push side to side.

If you have checked everything for loose connections, timing, cleaned plugs,checked for loose intake manifold or carb, replaced fuel & air filter's, etc....question......when was the last time you rebuilt/cleaned or had your carb rebuilt/cleaned? Today's fuels cause all kinds of problems with carbs........would probable be the cheapest thing to do or have done before you go through the expense of replacing other engine parts............

Distributor bushings are worn out. That is causing spark scatter, and cap terminal/rotor misalignment. Either have it rebushed, or get a new one.

If everything is new, then I agree your distributer is suspect.Soundhd also could have a point, so buy a can of carb clean, and aim the long red extension into the little jet holes on just under the top of the carb. the primary side AVS. there are two. I do it when running, and hold the throttle up. it may be that as well. NO ethanol in the gas, corn sediment messes with carbs. . Then, if no Improvement, I would purchase a regular points distributer from NAPA ,about 90.00 bucks for a good model. Don't buy the cheap Chinese version. I keep an extra around just to troubleshoot a defective electronic unit. Once you stabilize
the running, you can decide to repair the electronic unit. It is a lot cheaper than buying Electronic components and guessing. And they are handy to keep around. Driving to Phoenix once in my 71 Chrysler, the electronic unit crapped out in the mountains. all I had was a points distributer in the trunk. Thank goodness I packed it along. Miles from nowhere. At least then you can drive out of the state.Quickly, I hope.

hey sounds like a fuel delivery issue disconnect the fuel line , from the fuel pump to the tank , add short hose and run to a gallon jug on the ground with some premium fuel in it fire it up , should b able to rev it up with out any miss or hiccups if it does clear up theres your problem , if not replace fuel pump

I think SPEEDYRT1 is on the right track. Could be that the fuel filter (sock) in the tank has deteriorated to the point that it's partially blocking the pick-up. Once choke comes off, you may have a really lean condition, causing the problems you are having. BTW, OP said he replaced the carburetor with a new one. Have you pulled the plugs and checked their coloring? At any rate, doing the test above will confirm or eliminate the fuel tank / line as the problem.

69charger383 said:

I have a 69 charger 383 124000 original miles it started this miss /hestitation and part throttle , and like a slight bucking at highways speeds , now it has been converted to electronic ignition 20 years ago .

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I had a similar problem with rough idle, thought it was running on 7.. like a weird miss. Did all the same troubleshooting you have done. Tracked it down to ignition coil/ballast combination. I was running an MSD blaster coil with a resistor that had too high ohm rating (coil positive had low voltage) for that coil. Changed to a 0.8ohm and now it runs smooth as silk.

I had my MP electronic ignition installed by someone else,I gave him a MSD Blaster coil to use that came with a ballast resistor but I dont think it was used,looks like the one that came with the MP kit,should the ballast that came with the coil be used.my car runs and idles great but has a off idle stumble that I cant seem to shake.Im interested to know what is the right resistor.

red 69 runner said:

I had my MP electronic ignition installed by someone else,I gave him a MSD Blaster coil to use that came with a ballast resistor but I dont think it was used,looks like the one that came with the MP kit,should the ballast that came with the coil be used.my car runs and idles great but has a off idle stumble that I cant seem to shake.Im interested to know what is the right resistor.

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A good way to troubleshoot would be to take a multimeter and check voltages at the ballast resistor and coil. The high side of the resistor should be 12-14V with engine running, the low side should be around 9-10V or so as well as at the coil. I was running at 5-6V with the old resistor with the MSD, also with a cheap rockauto coil. The engine ran ok overall but would stumble some at highway speed and noticeably shook at idle because of misfire, I'm guessing because of occasional weak spark. MSD sells the 0.8ohm ballast specifically for that coil, I bought it from summit.

Try troubleshooting with a meter first before buying any parts. Good luck