EastYorkStang 63 Report post Posted June 20, 2018 Heard about resistance wires both for the tach and ignition. What happens if I don't do anything about them ? have a tach but I did put a duraspark/mad 6a box on my 351W. Quote Share this post Link to post Share on other sites
Mach1 Driver 560 Report post Posted June 23, 2018 There are two resistance wires on the car- one in the ignition and one to help drop the voltage to the gauges. You are referring to the one in the ignition circuit. To see how it works go to "How To's" on this forum, open the post "A REAL Schematic", and look at page one. The coil is normally run in series with the resistor wire. This drops the voltage to the coil and reduces the output voltage to the spark plugs- except when the engine is started. The resistor wire is bypassed by the starter solenoid when starting the car and it then runs the coil at a full 12v, which makes the engine easier to start. If you have a factory tach it is run in series with the resistor wire and coil. A Duraspark box and MSD 6A box are two different ignition systems.The Duraspark was made by Ford and used on newer cars, while MSD is owned by an independent company. To get an answer to your question it would have to be rephrased to indicate what ignition system and tach you are really using. Quote Share this post Link to post Share on other sites
ClubSport 29 Report post Posted June 24, 2018 The ford OEM tach is wired via the same resistance wire than the coil (+12V) when a normal tach its feed from the - side of the coil. I do not know about the need of the Duraspark distributor but a modern system ala ignitor 2 do not need the resistance wire or ballast resistor. The main purpose of the ballast / resistance wire is to lower the amperage draw thru points - mallory unlite has the same need except if the coil has more than 2.5 ohm resistance. You need to check the specs of the duraspark and if it can handle a 12V input you may bypass the resistance wire. Quote Share this post Link to post Share on other sites
