This question is actually for my boat distrib, but anything that would apply there would be applicable to automotive as well. As such I thought I might get a wider response down here, rather than up in the I/O forum.
I have a 'phasing' issue on my Prestolite distrib, ie, that is that the rotor position is a full cylinder contact stud beyond a given cylinder when the timing light verifies that it is firing, at idle. Consequently you can see the fire wear off the back side tip of the rotor as it tries to spark back to the stud. I have verified this because I cut a hole in the top of the cap, between the coil post and the #1 cylinder post and can watch the firing position with my timing lite.
This distrib has a Pertronix II ignitor in it and I have verified that the trip magnets are in line with the old point cam high points (for point opening) and all line up with the center sweet spot of the ignitor.
At first I thought that the issue may be due to the placement of the drive gear on the distrib but subsequent examination shows that regardless of the lateral position of the gear teeth on the distrib shaft (each tooth spans 24 deg's) the relationship of the rotor, the trip magnets, the ignitor sweet spot and the terminals on the distributor shaft does not change.
It seems the only way to affect the phasing would be to rotate the distributor cap on the distrib body to the degree necessary to align the rotor tip to the cylinder stud at the point of fire OR to rotate the ignitor plate (equivalant point plate) inside the distrib body. The later, of course, would back up the sweet spot on the ignitor so that the corresponding magnet would trip it sooner.
It would be nearly impossible to rotate the cap and keep it secure because the cap keys into the bracket that hold the tie down clamps. I even thought of drilling the rivits and repositioning the hold down brackets but they are thru rivited to the brackets that the ignitor plate is screwed to; so that would knock the plate out of its position if those mounts were moved along with the outer brackets.
As such, I took the only route I could see and that was to rotate and redrill the ignitor plate. I devined a degree to move it by and redrilled the plate. I started the motor and verified that the ignitor was now firing when the rotor was square in front of the cap cylinder contact stud. So far so good.
I then went to re-check my base timing which I had verified before the alterations. Low and behold, the timing lite was now showing that the firing was taking place about 40 or so degrees(visually extrapolated as there are no degree marks that far on the damper) before top dead center. I am even surprised the motor would run.
I do not know what is going on at this point. The position of the damper mechanically corresponds to the position of the piston at any given point so I know that when the lite trips with the pointer at the 40 deg btdc area that is where the piston is located at that moment and that is not correct.
Anyone have any idea what I am missing here? I'm sure not many have peered inside a distrib while the motor is running but I am absolute sure that the rotor, at idle does not want to be sending a spark out to a plug once it is past the contact that needs to get it there.
I have a 'phasing' issue on my Prestolite distrib, ie, that is that the rotor position is a full cylinder contact stud beyond a given cylinder when the timing light verifies that it is firing, at idle. Consequently you can see the fire wear off the back side tip of the rotor as it tries to spark back to the stud. I have verified this because I cut a hole in the top of the cap, between the coil post and the #1 cylinder post and can watch the firing position with my timing lite.
This distrib has a Pertronix II ignitor in it and I have verified that the trip magnets are in line with the old point cam high points (for point opening) and all line up with the center sweet spot of the ignitor.
At first I thought that the issue may be due to the placement of the drive gear on the distrib but subsequent examination shows that regardless of the lateral position of the gear teeth on the distrib shaft (each tooth spans 24 deg's) the relationship of the rotor, the trip magnets, the ignitor sweet spot and the terminals on the distributor shaft does not change.
It seems the only way to affect the phasing would be to rotate the distributor cap on the distrib body to the degree necessary to align the rotor tip to the cylinder stud at the point of fire OR to rotate the ignitor plate (equivalant point plate) inside the distrib body. The later, of course, would back up the sweet spot on the ignitor so that the corresponding magnet would trip it sooner.
It would be nearly impossible to rotate the cap and keep it secure because the cap keys into the bracket that hold the tie down clamps. I even thought of drilling the rivits and repositioning the hold down brackets but they are thru rivited to the brackets that the ignitor plate is screwed to; so that would knock the plate out of its position if those mounts were moved along with the outer brackets.
As such, I took the only route I could see and that was to rotate and redrill the ignitor plate. I devined a degree to move it by and redrilled the plate. I started the motor and verified that the ignitor was now firing when the rotor was square in front of the cap cylinder contact stud. So far so good.
I then went to re-check my base timing which I had verified before the alterations. Low and behold, the timing lite was now showing that the firing was taking place about 40 or so degrees(visually extrapolated as there are no degree marks that far on the damper) before top dead center. I am even surprised the motor would run.
I do not know what is going on at this point. The position of the damper mechanically corresponds to the position of the piston at any given point so I know that when the lite trips with the pointer at the 40 deg btdc area that is where the piston is located at that moment and that is not correct.
Anyone have any idea what I am missing here? I'm sure not many have peered inside a distrib while the motor is running but I am absolute sure that the rotor, at idle does not want to be sending a spark out to a plug once it is past the contact that needs to get it there.
This is for a Ford 5.0 with a roller cam. Timing the motor is not the same as 'phasing' a distributor. When you rotate the dizzy (to set base timing) the relationship of the firing point of the rotor tip to any given cap cylinder stud does not change. All that changes is the time of fire in relationship to the position of the piston and of course the valves.
