[robosparky]

I have a 67 Cougar with a 289 and dual quad carburetors. I just replaced the spark plugs (Motorcraft ASF42C), spark plug wires (Concours correct 7mm), and distributor cap. Upon starting and running the engine I noticed that there is arcing between the high voltage coil wire boot and the negative terminal on the coil. I am looking for suggestion as to the cause of this. By the way the coil is a Pertronix 1.5 ohm flame thrower. And the the spark plugs are gaps at .054 as I have GT40 heads. Please help?

 

[1970fastcat]

What type of ignition are you using? and what compression? The heads don't have anything to do with the gap, it's based on the power of the ignition and the compression. I think the plugs may be gapped a bit wide. Electricty acts like water in the respect of resistance. It will always find the path of least resistance. I would try gapping the plugs at .035 and see if that helps. If you have an aftermarket ignition then maybe try .040.

 

[robosparky]

Thanks for the reply. The compression is 9.75 to 1. I am using a vintage mechanical advance dual point distributor with a Pertronix Ignitor conversion kit which eliminates the points and condenser but still gives me the stock appearance. It is supposed to be a 40,000 volt ignition system with the flame thrower coil that I am using.

 

[1970fastcat]

I would probably go no higher than .040 or .045. With 10:1 compression, you may be blowing the spark out a bit with the plugs gapped that high. The cars that use .054 usually have 9:1 or less, plus they have an ignition box that boosts the spark a good bit.

 

[70_cougar]

The wider the spark plug gap, the more likely the spark is to jump to ground some where else. It is really that simple. When you increase the spark voltage, you MUST upgrade ALL of the components to contain the higher voltage or else it will jump to ground potential at it's highest potential point and that may not be the spark plug gap.

John

 

[robosparky]

I re-gapped the spark plugs to .040 and the problem is solved. Thank you much for the information!

Dean

 

[1969XR7Vert]

How about a bad coil tower (insulator)?

 

[Bad69cat]

That's why they do make a coil that has an extended tower to alleviate issues like that. You might try and use an insulator material first to see if you can stop it.