Startup Timing Setup

[Thumperbird]

I know as long as things are close an engine will fire and one can quickly get timing close to correct for initial warmup.
My question is more of a curiosity with a desire to minimize messing around during tha initial period so I can watch other things.  If a person wants to shoot for say 15 degrees advance at idle how far away from the electrode is the leading edge of the rotor tip?  I assume the spark will jump a fair bit as it gets close (msd ignition) so is 15 degrees advance something like say 1/16" in terms of rotor tip position prior to the cap electrode?

[blykins]

It all depends on how light the springs are and where you have the carb set. 

When I setup the distributor to start for the first time, I watch the exhaust valve open and start to close.  At that time the intake valve will start to open because of camshaft overlap.   I then look at the intake valve and when it closes, I shift my focus to the balancer.  As I keep rolling the engine over, I stop at 30° BTDC, then point my rotor at the #1 plug. 

Guaranteed to light off immediately if the carb has fuel and the ignition box has power.

[GerryP]

The setup:  In an inductive coil ignition, when the electrical field collapses in the coil, the current discharges to the secondary (plug wires).  What causes the field to collapse?  Some kind of circuit breaker, like a set of points or an ignition amplifier triggered by an electronic pickup.  Current from the electrical system is connected to the coil+.  In a points system, the wire from the points connects to coil-.  When the points open, the circuit goes to open and the coil's field collapses since there is no longer current feeding the coil.

That was the set up.  Here's why that is important to know:  You want the plug to fire with the piston at 15 degrees BTDC.  Make sure to do as Brent noted to make sure you are on the compression stroke with the cylinder ready to fire.  Set the damper at 15 degrees BTDC according to the timing pointer.  It should go without saying, but you are doing all of this by hand.  You are not cranking the engine.  You are turning it by turning the fan or with a socket on the crank.  Now, you want to take the cap off the distributor so you can see the points.  Connect a 12V test light to the coil- where the points wire attaches or you can just attach the test light to the points terminal.  Turn the key to RUN.  When the points are closed, you have a circuit and the test light with light.  With the points open, the test light is out.  The coil send current to the plug wire when the points open.  The closed part of the points is your dwell period and where the coil builds a charge.  The distributor's direction of rotation is counterclockwise.  You want to slowly move the distributor so that the points start at the closed position with the test light lit,  and to where the test light just turns off as the points break the circuit.  It is at that position the plug will fire and since the crank isn't turning, it will be at 15 degrees BTDC.  You can do this at any number of clockings on the distributor and if you do this and the vacuum can is in the wrong position, then you can either reclock the distributor or start in a different position.  Yes, you can do this in the reverse where you look to the moment the points close and light the test light, but it might be easier for this to be done using the moment the points open as your secondary ignition trigger moment.

If you have a breakerless ignition, then you do this with the reluctor spoke right in the middle of the pickup coil.