Re: Spark Plug Options for 71 Other Than Lectric Limited
Dick, we (me) is probably confused here. When the points break the field in the coil collapses and the secondary voltage builds (this is the rise time) until the plug fires. Until the plug fires the secondary is open circuit and there is no voltage drop in the wires, regardless of the wire resistance. What high resistance carbon wires do is limit the current when the plug fires and you do not get as hot a spark.
I'm not sure what you mean when you say the current flows to the cap all the time. When the points are closed the capacitor is grounded and does not charge until the points break. The capacitor reduces point arcing and coil ringing.
Ken, I have not heard about this rounded edge rotor. I know the long rotor is necessary to prevent misfires at high RPM. At high RPM there is not enough time for the coil to fully charge which limits the available peak voltage. The short rotor increases the arc gap and the coil does not produce enough voltage to jump the gap. This gap is the sum of the spark plug gap and the rotor tip to the distributor contact gap. This is saying that the RPM bandwidth of an 8 cylinder engine with a standard point ignition system is about 7500 RPM. In a small block Chevrolet engine at that speed the stock valve train is about maxed out, as is the strength of the engine bottom end. So that is saying the RPM bandwidth of a stock small block is about 7500, for several reasons. The valve train and bottom end in other 8 cylinder engines are probably not even that good.
Ken, back to the rounded rotor tip, voltage tends to build on sharp edges and will arc before a rounded edge. You are correct in what you say, but I'm not sure how this would cause misfires, unless it means that the spark jumps from the side of the rotor tip and not across the rounded end surface.
Enough typing for today. I'm done. We can continue this discussion tomorrow if we want.
-Dan-
Dick, we (me) is probably confused here. When the points break the field in the coil collapses and the secondary voltage builds (this is the rise time) until the plug fires. Until the plug fires the secondary is open circuit and there is no voltage drop in the wires, regardless of the wire resistance. What high resistance carbon wires do is limit the current when the plug fires and you do not get as hot a spark.
I'm not sure what you mean when you say the current flows to the cap all the time. When the points are closed the capacitor is grounded and does not charge until the points break. The capacitor reduces point arcing and coil ringing.
Ken, I have not heard about this rounded edge rotor. I know the long rotor is necessary to prevent misfires at high RPM. At high RPM there is not enough time for the coil to fully charge which limits the available peak voltage. The short rotor increases the arc gap and the coil does not produce enough voltage to jump the gap. This gap is the sum of the spark plug gap and the rotor tip to the distributor contact gap. This is saying that the RPM bandwidth of an 8 cylinder engine with a standard point ignition system is about 7500 RPM. In a small block Chevrolet engine at that speed the stock valve train is about maxed out, as is the strength of the engine bottom end. So that is saying the RPM bandwidth of a stock small block is about 7500, for several reasons. The valve train and bottom end in other 8 cylinder engines are probably not even that good.
Ken, back to the rounded rotor tip, voltage tends to build on sharp edges and will arc before a rounded edge. You are correct in what you say, but I'm not sure how this would cause misfires, unless it means that the spark jumps from the side of the rotor tip and not across the rounded end surface.
Enough typing for today. I'm done. We can continue this discussion tomorrow if we want.
-Dan-
Comment