coil wire length

[WV69RT]

Ordering a set of Firecore 50 wires and it asks for a coil wire length. Car is a 440 and the coil is mounted in front of the carb... Distributor doesn't look that far away and of course the car is two hours away locked up. Anybody know? Thanks!

[WV69RT]

The guy at firecore called me back... he said 10" was stock but he would go 12", hmm

[JB400]

I was under the impression shorter is better   Same as on the plug wires.

[WV69RT]

Any Firecore 50 guys out there? Looking at the Pro fit OEM 8.5mm set. Suggestions?

[A383Wing]

I made mine as short as possible, one for less resistance, the other cause it looks better than 12" of coil wire all over the place

Bryan

[MaximRecoil]

Use whatever length fits; if 10" fits comfortably there is no reason to use 12", though it doesn't make a difference either way.

High voltage from the coil travels along that wire; and the coil is capable of outputting voltage that's higher than the arc-over voltage of spark plugs (unless the plugs have excessive gap and/or are extremely fouled; in that case your coil may not be able to supply enough voltage to fire them consistently, or at all).

Arc-over voltage of spark plugs is typically 12,000 - 25,000 volts, and a good coil can put out ~45,000 volts. The plugs will draw no more voltage than is required to arc-over, and this fact gives you a lot of room for resistance in the wires. In fact, intentionally designing the wires with a certain level of resistance is the most common method that wire manufacturers use to suppress RFI (along with resistor plugs and capacitors [also known as "condensers"; a technically incorrect term that's pretty much only still used by the automotive industry]).

So shorter plug and coil wires do have less resistance, all else being equal, but when talking about minor differences in length, if you have a strong coil and good plugs, it won't matter.

7mm wires are pretty standard. Thicker wires such as 8, 8.5, and even 10mm are available if the insulation on a 7mm wire is too thin to handle the heat of your engine. Generally speaking, only race engines would be expected to generate enough heat in the vicinity of the plug wires to need thicker insulation than what's on standard 7mm wires. The thicker insulation offers no other benefit, aside from perhaps a cosmetic benefit.