1969 Dodge Charger Engine Problem...?

Question

I have a 69' Charger with a 383, New edelbrock carb and intake, slitely modified stock heads, headers, and dual exhaust. My problem is that when I go give it some gas, it always "coughs" up through the carb. When I say cough I mean that when I give it gas, a small amount of oil and crap come back up through the carb, into the air cleaner. On occasion this is so violent that it causes the engine to stall. What could be causing this? I have put a smaller carb than I had on the car originally (750cfm to 600cfm), and that helped a little, but not too much. I have heard that it could be weak spark or something of that nature, which could also be linked to its unlikelyhood of starting on cold mornings. Any input on this matter would be greatly appreciated. Thanks so much!!!

Timing is good...Problem pursists throughout range of timing. The method I used to set it was advance it till it pings, then turn it back a degree or so.

Could there have been bad accelerator pumps on both carbs? Plug wires are new MSD's, they shouldn't crossfire.

Thanks for all the great answers so far...just a few more details to add. I just redid the eintire top end about a year and a half ago, installing hardened valve seats, stainless valves, etc. Since that was so recent, I was kinda ruling out head trouble. Compression was good across the board when that was done also.

I ugraded the distributor to electronic ignition a couple years back, and now that you mention it that is when I started to have problems. I have had problems getting the thing to start on cold mornings since the new distributor was put on. Could it be a faulty unit? Also this problem is very bizarre in the fact that it is not constant. It only happens part of the time. I have been trying to track down this problem since I put the distributor on. That led to redoing the top-end, which led to the new carb, which led to new Optima battery, leading to new High-Output Coil, and dual exhaust, etc. Would a D.U.I (Davis Unified Ignition - Chevy style) Distributor help with the possible messed up distributor or should I stay with OE style (what is on the car now)?

Answer 1

Ewww... screwed up accelerator pump or timing is off? Sounds like timing is off.

Someone more knowledgeable should chime in. This is just to get you thinking.

Answer 2

To answer your question let's explore the relationship of your carb to the crankcase. How can the oil get back to the carb? Answer: via route of the pcv valve or through the intake. Lastly if the car is automatic and the modulator valve is bad it can suck tranny fluid up into the carb when accelerating as it would give more vacuum to tell the modulator to shift. Very common problem and if trans fluid is dirty would look like oil. First, check the pcv valve to make sure it rattles when you shake it and you can blow through it without oil coming out. Look at the inside of the hose as well to see traces of oil. There shouldn't be any if your engine doesn't have blow-by. To see if you have blow-by start your engine and pull off your oil filler cap. If air blows out you have blow-by which is basically where you have something which lets compression go into the crankcase such as a broken ring or timing problem between the cam and crank. Oil doesn't go into the cylinder to lube it contrary to popular belief. The crank slings oil upward under the pistons which lubes the cylinder from there. There is nowhere that oil is injected into the actual cylinder on top of the piston that it could blow back up into the intake unless you have a head problem which we'll cover in a minute. A broken oil ring would let the oil leak up into the cylinder in various quantities depending on how bad the break. The vehicle should smoke as well if this is the problem. If your car is out of time a little bit or valve stem seals are bad you could get the problem you are talking about. For oil to come up through the intake into the carb it would take multiple problems working together such as oil leakage into the cylinder and then an intake valve being partially open on compression stroke so the oil could be blown up into the intake. Do you see where I'm going with this? If the intake valve is truly shut like it is supposed to be there is NO way the oil can blow out of the cylinder into the intake but instead will be blown out the exhaust valve. If the valve stem seals were worn enough for oil excess from the heads to slide down the stems into the cylinders and the cam to crank timing was a little off where the intake valve was a little bit open when the compression stroke started you could get this problem, but that's about the only explainable way unless you have a cracked head or block. The blow-by theory or tranny fluid coming up through the vacuum on the modulator is most likely. Hope this helps

Answer 3

several things come to mind and the first recommendation is to put the ignition system on an scope [remember electricity is lazy it seeks the path of least resistance] a warm engine at idle [with fuel mixture close to optimum] only requires 16k volts to fire, so look for high or low firing lines and remedy these first.
now check for ignition available [use insulated plug wirer pliers] pull coil wire out while running and see if firing line reaches your aftermarket manufactures specs [remedy as needed]
next momentarily go to wide open throttle with display in a stacked [raster] pattern and see if the spark scatters if it does suspect pick up coil/reluctor trigger issues [a wobbley shaft /bearing or too much thrust play in dist shaft can cause this
at this point if all checks good suspect not enough accelerator pump volume/rate note with most aftermarket intake/carb combo's you will really have to pump the heck out of it then wait 5-10 seconds before attempting to start it when cold.
one last note on big block chryslers i have seen induction firing of plug wires between cylinders and accross banks the cure for this was to purchase a grounding kit [metalic flexable covering that slides over the plug wires before you put the terminals on then a gang static loom [metal] 1for each bank and one for the coil wire exclusively each containing a braided ground strap that is fixed to a central ground point [not phisicaly close to battery ground point]
always the steps are mechaical condition [rings/valves/cam timing/lobe condition] then sort out the ignition completely before piddling with fuel. TEST DON'T GUESS
note 10/25/07 the d.u.i. is a reliable unit and a good choice over the mopar stock electronic unit

Answer 4

It sounds like a choke problem to me.When I run edelbrock carbs I usually have to run them with the choke partially closed.A wise investment for the edelbrock carb is the strip kit and tuning manuel.Hope this helps.For craig H Chrysler transmissions do not use a modulater valve.Also if you have a high performance cam I've found that plugging the vacuum advance and turning the timing to its highest idle and backing off slightly is the best timing.I have had friends time my car with a light and ran it then I timed it by ear and they always run stronger when timed by ear.I always leave the vacuum advance disconnected.

Answer 5

I agree with most that it is a timing problem.

How long ago did you go thru the distributor? Are you getting any advance when giving gas? Sometimes the weights get stuck, and/or the vacuum advance diaphram breaks and the advance needs to be replaced. Also. Is your vacuum advance vacuum line cracked, broken or plugged in any way?

Easy check, put a timing light on it, remove vacuum line, accellerate and timing should advance to check weights. Have timing light light on when connect vacuum line to check the vacuum advance. It should bump up or down if you plug it in and disconnect it.

Also. If this is a '69, and not converted to elect Ign, how are your points/dwell? Could be just running to close on point gap and arc'ing

Answer 6

Since you mentioned coughing up through the intake, your problem is most likely timing, which you already claim to be correct, or an intake valve not seating correctly. Do a compression check on all cylinders to rule this possibility out or pin point the bad valve.
It should not be this difficult to isloate your problem since it's an older, classic vehicle.

Answer 7

you have a lean fuel mixture concern i suspect pcv valve stuck open. simple test, remove pcv valve and plug line with a 3\8 bolt. to check the accelerator pump with engine off look down the front 2 barrels of the carb and cycle the throttle to open watch for 2 streams of gas if it just drips replace the diaphram. let us know what you find sweet ride by the way.

Answer 8

Set your timing correctly, not how you describe. Get an advance timing light, plug the vacuum advance, and set total timing at 3000 RPM, somewhere around 30 degrees. Recheck all the wires for correct firing order, you can get 2 crossed and have these symptoms.

Answer 9

the first answer is correct..

my guess is the accelerator pump is coming in to late..
or is delivering too small a shot..
it could be ignition timing as well

i have seen cheep plug wires cross fire and do the same thing

Answer 10

Check your timing. It sound like its a few degrees slow.