For the life of me I cant figure out why it does this. I was having problems with my engine (65 327) not running on all cylinders...missing/rough idle. I started pulling plug wires one by one to narrow down which werent doing thier thing. When I pulled the non firing wires half way off the spark plug the engine would idle faster and smooth out. When I pushed it back on it would quit firing, or fire sporadicaly...pop...pop. I have a stock distributor with a Mallory Unilite conversion, stock coil. I thought it may have been the plug wires I got from Auto Zone, but stuck a few 8.8mm sidewinder wires I had around which improved it some, but still does it.
Do I need dielectric grease on the plugs? Is there supposed to be a resistor somewhere? Whats going on? Im perplexed.

This may seem stupid but I'm sure that most of us have done it: Have you got the firing order right? If you got two cables mixed up, it may idle pretty good on the 6 cylinders that are hooked up properly, but will start acting up, backfiring etc. when the remaining two are connected to the wrong plugs. Just an idea, I have learned the hard way to always look for the simple things first...

Firing order, distributor, timing right on. When I completely remove the wire, the cylinder dies, the engine stumbles. Its when the wire is half way on the plug is when I get a good spark. Push it all the way on and it misses again.

Start by swapping the misfiring plug with one thats working ok to check for a bad plug. If the problem moves with the plug, the plug is bad. Check the inside of the cap for carbon tracks. Check the rotor too.

graemlins/beers.gif graemlins/clonk.gif smile.gif :( redface.gif :D ;) tongue.gif

Bad,
How did you "check" the plugs ?? The plugs that start firing when you pull the wire half way off are doing so because the gap from the wire to the plug end causes the ignition to build up more voltage before jumping the gap. This allows it to fire a partially fouled plug. This was the theory behind the old booster gap plugs that were designed to run even when oil fouled. Try swapping the plugs with new ones and see if it works. Let me know if I was wrong.

Bad,
I did a google search....heres a link that has a pretty good explaination. Scroll down the page to the "Booster Gap Plugs" section:
http://www.castensdynojet.com/sparkplugs.htm

Thanks for the link Bill. Now I understand whats happening. It was a very educating read. When I said 'checked' the plugs. I found they were fuel fouled. I cleaned them back up, but the problem would come right back. I had a complete MSD system in my other Chevelle. I had a new set of plugs laying around from that car so I used them on this engine. They are AC R45TS plugs. Im thinking I have the wrong heat range for my application graemlins/clonk.gif .
Obviously without a "HOT" ignition system I need to choose more wisely :confused: . Thanks again smile.gif