George,
It does not electricically negate it at all. It is very much in force if it is activated. What I mean is if you spin the motor over and flip the switch it negates any possible benefit of using it and can be more destructive than good, becuase the thing is still with a retarded spark no matter when you flip the switch. If you are going to spin and flip the switch completely disable the start retard and do not allow it to do any retarding. It is designed and works very well at retarding the ignition a set number of degrees the same as if you were manually twisting the distributer to retard one to get it to start.
The spark is not delayed. It is the time it takes the trigger signal to get to the power supply that gets delayed. In the original versions we were using resistors of different values shunted to ground to delay the trigger for either starting or for the extra high gear retard. These resistors of different values were labled simply as degrees. Different values were different resistances. It was the same way in essence the rpm rev-limiter worked, each different chip was a resister of a different value.
I have a customer with a hard head that refuses to use the retard and he also spins and flips and he keeps knocking teeth. I have told him the same I am telling all of you. Before we had a start retard we then did spin and flip and we ocassionally lost teeth and at times bent rods. We means all the racers of those edays before MSD.
Just think if you will. How can an engine possibly kick back. What can cause it. With a regular car timing too far advanced will do it. Why? When you change the timing either by manual, mechanical, or electronic means, the rotor position when fire hits it is also changed. IF it is easier for fire to jump to # 8 or # 2 it will before it will jump to #1 which is under pressure. So the rotor does not have to be far away from center #1 position to jump the fire to either #8 or #2.
If you have your rotor lined correctly in the right spot and a locked distributor it will be centered at #1 coil terminal at your maximum timing. Retarding it will move it away from ideal center but not so far that # 1 is still not the preferreed cylinder to fire. IF you have for example a 30 deg locked distributor and it is locked at 30 degress advance but it is a N2o motor, so you are mostly at maybe 15 degrees advance all the time. or maybe even at 20 degrees.. So even with rotor phased correct for nitrous use it would still be very close when retarding from total timing with no N2o. Actually it would be almost dead center or close to it with the start retard but not the nitrous retard. So ignition wise there is no way it could kick back.
Now if you were to take the secereo I just outlined in the above paragraph and were to still have the ignition retarded for starting only and were to spin it and flip the switch, the first or next cylinder to come up should be the one to start the starting process with or withour retard, but not so. Becuase then that cylinder has already hit and gone past TDC becuase of the retard and the next cylinder to fire is likely a piston on the way up and not ready to fire or worse yet a cylinder with an open valve. Remember the engine only fires every 90 degrees of rotation. So depending on where in rotation it is when you spin and flip will depend on what happens afterwards. Excess fuel in the cylinder is a sure way for a kick back. That happens far more frequently than you can imagine it does.
IT was becuase of parts breaking that we came up with the retarded start in the first place. Usually it was a starter or flywheel tooth. At timmes guys had rods bend. Most of the time they all got away with it no problems.
I know that the newer Digital Boxes are not working exactly the same but I think the concept of it is. I know the guy who created all the Digital Boxes, I am thinking about talking with him about what you all are saying and maybe someway it can be switched of and on like in the old days instead of being rpm sensitive. Maybe that can be an issue, come to think of it.
Ed