70Coronet

So I got the coronet running and took my first test drive went about 5 miles ran great, shut it down checked everything then went on a longer ride to attempt to get some miles on it b4 getting my foot to deep into it. Drove about 25 miles nice and easy made a stop at inlaws shut it down then fired it back up and goosed on iot for about a second and drove it another 25 miles home-the entire time it ran perfect! Then took my kids for a ride about 5 minutes after shutting it off and it developed a miss that I can hear throught the exhaust and feel in the car at about 2,ooorpm and higher. I turned around popped the hood and sure enough two plug wires cylinder #5 and #7 had the plug wires fried against the header. I replaced both plug wires thinking atleast it was a easy fix until I test drive it and it did the same exact thing, checked wires again swapped plugs out and it looked like cyl 7 was a little wet the rest of the plugs look a little lean with a tint of white/gray to the plugs. Car info 70 coronet 360-408 engine healthy cam(rough idle) 10:1 compression new dist. new ignition module(both failed before any of this happened) edelbrock 750 carb-choke not hooked up but still on carb---Please if anyone has any ideas please let me know!! Thanks

bremereric

Sounds like number 7 is dead and not firing. Probably a bad spark plug wire. You can ohm it out with a meter or test it for spark the old fashioned way.

PK1

1. Make sure they arent crossed on dizzy. Maybe you have them swapped. Happens us all.
2. Test for resistance in the wire.
3. Check for other burns on all wires.
4. Gap set correctly?
5. Is primary and secondary voltage within spec on the coil?

ryan

Wires can get really expensive ither wrap the hedder really well on the tube or get a good heat barrier for the wires to slip through or both. Good luck. I burned a few wires up before I got tti hedders

bremereric

DEI makes spark plug boots and heat wrap for wires.

70Coronet

I already replaced the wire-twice to be sure and put a new plug in, noticed last night rotor has burn marks under coil contact and on the inside of the cap at the coil terminal it is black and burnt looking-gonna try a new cap and rotor tonight-wires burned through open wire grounds on headers causin burn inside dist cap/rotor?????
EDIT: Is it possible to have the wrong cap on the worng dist., upon starting the car originally I had to get a new dist. the little gear under the rotor had nicks in it causing no spark-so at about 8pm I called o'rielly and they found a dist out of a 78 dodge pickup-dropped it in put my old(new) cap on the new dist which looked identitcal and it fired and ran great till this issue with burning the wires-about 50 miles worth of driving=-thanks for all the help guys!-I do have the sleeves on the two back cylinders but with the original style straight boots the wires were almost laying on the headers-now I put 45 degree boots on both rear cylinders giving me about an inch or so of clearence

PK1

Sure, if the cap sits high or off centered the rotor wont make contact to transfer spark energy. Or resistance in the energy train causes it to not pass. Sounds like your are already leaning towards this.

You can place both caps on a flat surface upside down. Run a straight edge across the bottom and measure to rotor tip. That will give you an idea. However most rotors have spring loaded type arm for center post contact to take up for machining tolerances ( or lack of ) if its a slightly different cap.

You can also coat all the internal posts with a black sharpie and install and crank motor. The contact from the rotor will remove the marker or "witness mark). If one terminal isn't getting contact then the shaft or shaft bearing may be out of round or the mounting ears for the cap are distorting the shape of the cap.

Do not discount a weak coil. Test it. Search for it. There is a detailed walk thru on here with picks. A weak coil will fire a car but indicate show as mis fire on the wire or terminal with most resistance.

I dont understand the "nicks" thing? Can u post a pick?

I would also run an inline spark tester on each wire at the plug and run it. At least make sure it is a "no" spark condition and identify the one or ones.

70Coronet

The cap is not sitting right on the dist. when I set it on it doesnt sit down flat its like its sitting on a rounded surface-got the new cap and rotor on with the help of my wife to get it on straight-runs great now-but its not technically fixed-gonna have to put some time into getting the right cap or maybe a msd or something

440roadrunner

The same cap should fit both dist.s Some caps ARE tight and might rightly be called a "press" fit. This is an individual cap - to - cap thing, not by design. And of course nowadays with quality going downhill.........................

70Coronet

Just an update still running good-finally got a video of it but its says its to big to get it off my wifes phone