small block oil priming question

[cudamark]

I disagree, or maybe our definitions are different. The rotor phasing is going to change regardless of whether vacuum advance is connected or not, due to the mechanical advance. Now spark phasing, if you will, will change with both too. When either advance is working, the spark happens sooner, and the rotor will be at a slightly different spot in relation to the cap terminal. The vacuum advance just works the plate, which advances the spark. It doesn't change where the rotor is pointed, just causes a spark sooner. I guess I need to expand on what I mean. I consider the initial rotor phasing to be with the engine either off, or, at idle. Neither mechanical or vacuum advance in play. With a rise in RPM, both vacuum and mechanical advance start to work. Vacuum advance moves the point/reluctor plate advancing the spark, but, not moving the rotor from it's initial orientation. With the spark happening earlier, it will often jump the gap in a different spot on the rotor to maybe a slightly different spot on the cap contact. When mechanical advance kicks in, the upper part of the shaft rotates on the lower part of the shaft, thus changing the physical position of the rotor in relation to the slot in the drive gear/shaft. With this change of position, the spark will also probably jump across the gap in a different spot on both rotor and cap terminals. In severe cases, the spark my also jump to a different terminal in the cap causing a backfire. The design of the cap, rotor, amount of advance degrees, resistance in plug wires, spark plug gap, coil output, etc, will play a part in whether that backfire happens or not. One of the vehicles I owned and drove had a 400 engine with factory electronic ignition. The only way I was able to get rid of the backfire was to modify the reluctor to change the initial rotor phasing. I'm reasonably sure I could have also done it by modifying the distributor too (by changing how much vacuum and/or mechanical advance I had), but, the reluctor mod was the cheapest and easiest way to do it back then.

 

[Dartfreak75]

Technically, doesn't it go in 2 ways ?
(The right way, and 180 degrees of)

The reason I mention this is, if it truly only goes in one way, then "in is good"

The dissy can be 180 off not the gear as long as the slot is facing the correct way for the distributor slot to go into correctly then it doesn't matter. The only reason the direction of the slot is important is so you will have ample space to move the distributor when setting timing, and to make it easier to get the plug wires right. You can make #1 wherever on the cap as long as the wires are moved to correspond.

 

[Rapid Robert]

CudaMark like you I redrill the reluctor roll pin hole when I need to alter rotor phasing & my def of it is, where is the rotor in relation to a cap terminal when it fires. Can I persuade you to drill a hole in a cap & try it.

 

[cudamark]

Yes, I think we may be splitting hairs here, but, to me it's more a mechanical thing rather than an electrical one. They all have to work together though, if you want a proper spark at the correct time so you don't get a backfire. Since I no longer have a phasing problem, I'll leave the experiments to others.