The Stovebolt Site Forums The Shop Area Engine Shop Spark plug wires

What sparkplug wires are recommended for a 54 3100 without radio etc. No need for resistor wires. Historically, I just made wires from a roll of alum spark plug wire. Worked at the time. Suggestions? Have built a 235 from a 57 Nomad.

Metal core wires cause the carbon center button in the distributor cap and the tip of the rotor to erode rapidly. As long as you don't mind changing the cap and rotor at every tuneup, run whatever floats your boat.
Jerry

Jerry... what would you use?

I've been using string-core resistance wires for 50+ years, even on 700+ HP round track racing engines. The idea that high performance or antique engines need metal-core wires is a myth.
Jerry

That's interesting. Never really thought about it before.

The Internet says a typical modern spark plug has around 500 to 3000 ohms. 500 ohms new and increases as it ages.
Modern spark plug wires have between 10,000 to 12,000 ohms (typically).
A solid copper or aluminum core wire would have a few ohms or less.
So a lot less resistance (500 ohms versus 10,500 ohms for example) means a lot higher current through the parts along it's pathway.
It takes voltage to fire a spark plug (around 3000 volts).
It takes voltage to jump the gap from the rotor button to each cap electrode.
So the increased current (more than needed) would negatively affect the parts that move and parts that arc, more than the others.
The other parts would have to dissipate more heat.

I think Jerry's statement has some merit.

As with a lot of other automotive electrical system situations, firing a spark plug is not a simple resistive circuit with constant current flow. To initially ionize the gap(s) at the rotor and the spark plus electrode and get the arc flowing, a voltage of somewhere around 7-10 KV is required. Wide plug gaps, rounded electrodes, and loose or corroded connections need more voltage. Once the arc is established, that voltage drops considerably, down to the 3-5 KV range. This current flow continues at the lower voltage until enough of the induced voltage in the coil secondary is lost that the arc cannot be maintained any longer. Then the residual voltage left in the plug wire bounces back and forth from the plug terminal to the distributor cap, losing a few volts at each oscillation. A resistance wire can have up to 1K ohm per inch, which dissipates the residual voltage more quickly, preparing the conductor for the next firing impulse. Since a spark plug fires approximately 60 times per second at 2K RPM, getting rid of that voltage ripple quickly actually makes a resistance wire more efficient than a metal core, plus the current flow is reduced and parts last longer. That "hot blue spark" we used to look for was actually pretty destructive. Resistance wires produce a yellow/orange color spark that lights off the gasoline in the cylinder just as efficiently.
Jerry

Jerry as usual, you are spot on with your advice.

Thanks, Jerry... guess I'll use the metal core wires on the Johnny Poppers and get good resistor ones for the 235.