The extra 5 degrees was to provide for the stock split.  One VR drives the leading plugs, the other drives the trailing,
  each sensing for a separate EDIS-4 module.

In a message dated 5/1/2011 1:26:28 A.M. Paraguay Standard Time, echristley@att.net writes:

 

 

OK.

I missed that. Sorry.

 

Most engine builders don't bother with the split. It has time to work at low speed where more mixture is forced into the cavity in front of the plug, and then you get a flame thrower effect when it fires. Not the case at speed, so it is for emissions for the most part. Some builders drill the hole bigger. Some builders mill a slot the same size as the hole

laterally about 5/8" each side, to get a flame out and spread a bit at high speed. No doubt that some mixture makes it into the cavity at speed and is ignited but it adds little to the power. You can fail the trailing system and not notice it. Not the case with the leading system.

 

A surface gap plug recessed just enough to miss the apex seal would be better but still you need it behind a bit of wall with the slot idea, as at low speed there is a possibility that you could leak burning mixture across the plug opening and ignite the next charge prematurely.

 

In boosted engines that split starts to look like a detonation event, so again fire both at once.

 

That problem firing a double ended coil is the gap size on the plugs. Us plugs you can change the gap on, and set the gap at .010" to .015".

 

I used those even with an MSD and never had the problem. Remember the rotor is hauling the mixture past the plugs like a freight train.

AR2592 Autolite work fine. Same heat range as NGK -10s. But usually $7.00 a box of 4 at Autozone. The open tip may get better cooling than the NGKs

 

Lynn E. Hanover