GM-GMC: Eng. miss?, gmc pickup, reputable shop

Question

Dear expert,


I am currently working on a 86 Gmc pickup with a 4.3 litre emge w/ less than 005000 miles on the eng. rebuilt by a reputable shop. It is my father's truck, so when he told me he had problems I listened undoubtedly. He had said it ran rough, {he's very full of pride so I don't suggest anything) he would do a tune up. Two weeks later(or there abouts) he has problems, the engine runs extremely rough. After a week or so of "dealing" with it, he suspects the head to be culprate and after a self done compression test shows 60 lbs of pressure in the sixth cylinder I aree to help replace the problem. I remove the head to find
A brass something screwed into the spark plug hole. Dad suspects sabotage! I within moments, recognize the object as a fitting for a compression tester. He had tried to drill it ou and tap it for to fit a spark Plug! I assume he was crazy all along and replace the head, fix a bunch of rotten vacuum and wire routing. The truck tunes out quite well, but after 45 minutes of run time the truck misses badly. We argue, he goes unwillingly to buy plug wires and a dist. cap and rotor. His tune up had inc. plugs and wires. The cap and rotor were obviously, to me,  well thaught of as having tune up come back potential. The wires shocked me when I adj. the timing so I explained they may be cossfiring. Anyway when I got to the 6 cylinder plug wire, I noticed the tower on the dist. was crooked and loose. the plug wire broke @ the plug, I did a compression test to show 150 lbs in the 6 and 4 cylinders. Could a tower that was not completly broken cause the eng to miss the 6 cylinder?
I will find out tomarrow I guess reguardless, just frustrated looking for another's perception. Do you think I should have ? my father's abilities that have never let me down. I mean, I guess we all have bad days right? Please hit me back, I could use the comfort. Thanx!

Answer
Chris,

Ever since 1974, GM has used a high energy ignition system.  ALL of the parts involved including the plugs, wires, cap, rotor, and coil MUST be in perfect condition in order to deliver the high voltage spark to the cylinder.

GM even warned mechanics with heart trouble or pacemakers to be extremely careful when working around their ignition systems.

So, yes, a cracked or damaged plug wire tower in a distributor cap can cause a miss.