The #6 spark plug wire was not grounded to the engine when it is disconnected at the spark plug. Please explain your concern about not letting the wire hang loose and grounding it to the engine. The firing order is 162435 clockwise and it has been checked.

When you do not ground the wire to the engine (or body), the spark energy will arc inside the distributor or coil, eventually damaging it. In old cars with low energy points ignitions, this wasn't a big problem (although I still wonder how many of my "bad coils" 30-50 years ago were caused by doing this). With high energy CDI and transistor ignitions, it will damage the coil.

Recommend that you get a "spark tester", which is a short length of spark plug wire with a spark plug top on one end (to insert into the sparkplug boot) and an alligator clip at the other end (to clip to ground) with a clear plastic cylinder in the middle with a short gap inside so that you can see the spark. FLAPS sell them cheap.

I have ordered the spark tester.

The distributor has been rebuilt and has a #1867S Pertronix module, #40611 Pertronix coil, 911.609.06100 spark plug wires, the factory CDI box checked. Spark plugs are NGK BP7ES

I've puzzled about this some more. It's really odd that connecting the #6 plug wire would cause it to run worse. I know you said you checked the wire routing. I'm wondering if there is some kind of carbon track inside the distributor cap, or a bad wire set passing the spark from one wire to another where they touch each other. Try separating the wires with cardboard. Is the cap new or old? Bosch or something else? have you swapped plugs and wires around to see if the problem follows the plug or wires ?

Try swapping sparkplug wires and/or plugs with another cylinder, and see if the problem follows the swapped parts

I will try separating the wires with card board. The cap is Bosch. I have tried swapping the spark plug wires with another. I have tried swapping the spark plugs.

Lauran

The only other thing I can think of to try is to remove the Pertronix and go back to the original distributor parts. Otherwise, I'm out of ideas.

I have added two quarts of Marvel Mystery Oil to my ten quart capacity oil pan and remote oil cooler.
I have also added 3 oz of Marvel Mystery Oil to 7 gallons of gasoline in my fuel tank. The engine seems to be running smoother with the addition of the Mystery Oil. I hopeful that the Marvel Mystery Oil will help with any valve sticking that my be occurring in the engine.

Watch your oil pressure. Marvel's is much thinner than 20W-50.

They would get you in the ball park if you lacked the more accurate tool. If you're doing this whole affair in the car, you'll likely need a borescope tool or mirrors to read the installed height.

Just use a digital caliper. Measure the thinnest (outside) shoulder if the retainer and zero the caliper. The. Install a weak spring with shim pack and spring seat, keepers, etc. measure from the top of the retainer to the spring seat. That is your spring installed height

I believe that adding Marvel Mystery Oil to my crankcase and fuel tank has solved my problem after two years of investigation. Thanks to all for their suggestions. Lauran

Well done. Sometimes it’s the simple solution.

Hi, I am in the process of setting my spring heights. The engine is out the car. I thought there were only 0.50mm shims available? Can anyone give me the part number for the 0.25mm shims mentioned in this thread please?