I have a 330 high compression engine with a HEI ignition. All of the plugs fire, but I have a miss and it makes no difference when I remove the #8 plug wire. The plug fires out of the engine. I have swapped with known good wires and plugs. Any ideas? Thanks.

 

Have you checked for a Leak in the Intake Manifold.

 

You need to see if there is compression in that cylinder and that the valves are opening and closing. If you have all of this it is then an ignition problem. You could have a flat lobe on the distributer for that cylinder. Just because a plug fires outside the engine doesnt mean it wuill fire under compression.

 

Sometimes it can be the simple things.
Check for a cracked spark plug or cap.
Did you try new a new wire, plug and cap?
You do need to check compression on 8 if
you think that is the bad one. Cracked ring?

 

If you have fire to the cylinder like you say you do then you have a mechanical problem of some sort.

 

Totally true! I once had a Chevy pickup that ran rough when I bought it. Did a complete tune-up, plugs, wires, cap, rotor, condenser, points, and still ran rough. Added an HEI dist with Accell Super Coil, and new wires again, still ran rough. Swapped the heads and cam 'cause compression was slightly low on one cylinder. Still ran rough!!! I was sitting on my living room floor mumbling to myself when my wonderful Wife asked me if I had changed the plugs? "That was the first thing I changed!" "So change them again, they aren't expensive are they?"

I used standard AC plugs the first time and they had maybe 200 miles on them. I replaced them with AC Rapidfire plugs and that engine ran like stink!

Always, always, ALWAYS use the best spark plugs you can!

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I did find a small leak oddly enough right on the corner above #8. I will fix that tomorrow and see how that does.