Boy, this has been one wild time figuring out this misfire.
When the misfire started, it would be running fine, then start misfiring. I could shut it off and turn it back on and it would run fine. This would happen every once in a while. Suddenly, one day it started misfiring and would not quit.
I was thinking "Cold day, coil pack went." so I replaced it...still ran like crap.
One day, a buddy and I were troubleshooting it and changed out the plugs. Fired it off and heard a cluck that almost sounded like a backfire and I shut it off right away. Pulled the plugs and they were a tad longer than the ones I took out.
To make a long story short, we got the right ones. Fired it up and it still had the same misfire as before, acted no differently.
Today, we were changing out the CPS and noticed the oil pump drive shaft that the CPS connects to (for you distributor guys it looks a lot like the gear on the end of your distributor) and it had some play in it. Got a new one and replaced it. Then it was running quite a bit better but still not quite right...rough and still seemed to have a different "feeling" misfire, for lack of better words.
Pulled off the valve cover and lo and behold:
So basically, the oil pump drive shaft and the CPS was the source of the original misfire and the spark plug incident was the source of the push rod failure (that was the loud cluck that we hear that almost sounded like a backfire through the throttle body.) Funny thing is, the plug had no damage. I think the piston is fine. I have a feeling that the valve came down and hit the side of the plug and since the pushrod is softer, it is what gave.
New push rod will be here in the morning. I hope no more damage exists..........looked down in the push rod hole as best as we could and cam and all still look good so my fingers are crossed.....