Adjusting Rotor Phase on Duraspark Distributor

[basstrix]

Do any of you know what is available to adjust the phase on a durapark distributor? I've seen where a guy drilled and tapped the reluctor for a set screw so he could rotate it wherever he wanted. Have any of you tried that? Seems like it might be unreliable. I've seen adjustable rotors, but, so far, not for durapark. Another option might be to do something with the breaker plate....either by moving the pin where vacuum advance arm connects or something to the vacuum advance arm.

If you know of a method that works, please post up.

 

[basstrix]

Here's a picture of a reluctor with setscrew installed. This is not mine, but I'm considering this....if nothing else to determine the optimized clocking.

 

[TommyK]

I have heard of people bending the teeth on the reluctor but haven't done it myself.

 

[basstrix]

I have heard of people bending the teeth on the reluctor but haven't done it myself.

Yeah, I've heard of doing that when the trigger points aren't all precisely 45 degrees apart. The example I saw was checking timing on #1 and #6 since they both would flash TDC on the balancer. I'd be afraid of snapping off a blade.

 

[boilermaster]

basstrix,
How far off are you ?.
are you checking mechanically or electronically?
if electronically, leading edge or trailing edge ?.
When I was running duraspark, I simply rotated to my all in timing with timing already set and rotated advance assy. against spring tension and
low and behold, I was right there, still cannot remember if I was on leading or trailing edge.
Any possibly what so ever the run and crank wires to the module are reversed?.
Boilermaster

 

[basstrix]

basstrix,
How far off are you ?.
are you checking mechanically or electronically?
if electronically, leading edge or trailing edge ?.
When I was running duraspark, I simply rotated to my all in timing with timing already set and rotated advance assy. against spring tension and
low and behold, I was right there, still cannot remember if I was on leading or trailing edge.
Any possibly what so ever the run and crank wires to the module are reversed?.
Boilermaster

Not sure how far off I am just yet. I cut a hole in a distributor cap and used a timing light to see where the rotor was when it fired....but I forgot to zero the advance on the light so my observations are off by 13 degrees (where the light was set for base timing). Dought!

I thought maybe the polarity was reversed on the pickup coil so I made a cable to reverse the polarity. Reverse had the affect of advancing rotor position by approximately 20 degrees.

Here's the problem, when I am cruising and engine is above 3000RPM, the tach signal on my data acquisition gets very noisy. The signal is relatively clean at wide open throttle. I can modulate the noise using a hand vacuum pump connected to vacuum advance. This made me think it's related to rotor phasing. The diagram is an attempt to illustrate what I see.

The puzzling part is that I don't feel or hear anything when this is occurring. When I modulate on and off, I can feel a slight difference....the car slows a little. When I reversed polarity, the engine started popping and ran very poorly.

 

[Don C]

Check the condition of the breaker plate bushing. If it is worn it will change the spacing between the reluctor and pick-up coil as it moves back and forth. Check the gap between the reluctor and pick-up coil.

 

[basstrix]

Check the condition of the breaker plate bushing. If it is worn it will change the spacing between the reluctor and pick-up coil as it moves back and forth. Check the gap between the reluctor and pick-up coil.

Thanks Don, the distributor is a new Cardone unit and bushing is nice and tight.

 

[Don C]

Thanks Don, the distributor is a new Cardone unit and bushing is nice and tight.

One other thing comes to mind. The DuraSpark box receives its ground from the pick-up coil (distributor module), which is grounded to the distributor body via a small brass ground strap under the wire grommet on the opening in the distributor body. Check to make sure that ground is good. It has one screw in it.

 

[boilermaster]

basstrix,
Would like to see what the tach signal looks like with the vacuum advance disconnected and plugged.
Your rotor phasing could simply be worse on the low end, and gets
better (closer) as the mechanical advance (rpm) increases.
My experience tells me that rotor phasing is usually poor running at very low rpm or misfiring at very high rpm, your case is odd to say the least.
Boilermaster

 

[basstrix]

basstrix,
Would like to see what the tach signal looks like with the vacuum advance disconnected and plugged.
Your rotor phasing could simply be worse on the low end, and gets
better (closer) as the mechanical advance (rpm) increases.
My experience tells me that rotor phasing is usually poor running at very low rpm or misfiring at very high rpm, your case is odd to say the least.
Boilermaster

Here's the signal where the vacuum advance is disconnected & plugged. The dashed blue line is 3000RPM, which is the point where the noise (or whatever it is) begins.

Edit: 3000RPM is also the full-in RPM for centrifugal advance....I'm not exactly sure when it's all in, but somewhere between 2500 and 3000. I re-curved using the Mr Gasket 925D springs.

 

[Sheriff41]

@mrgmhale used to work in the DuraSpark systems for Ford dealerships. Maybe he'll join in and lend his expertise.

 

[basstrix]

@mrgmhale used to work in the DuraSpark systems for Ford dealerships. Maybe he'll join in and lend his expertise.

I actually started by sending him a private message. I think he must be traveling or something as that was about a week ago.

 

[tony-muscle]

The only way I can think off is rotating and locking the breaker plate's "zero advanced" position. It would work only in the advance direction though. It will also mess with the mechanical advance. I thought about this if I need to lock out the distributor for my FiTech.

 

[basstrix]

I'm going to try and get some pictures of the rotor vs terminal....this time with the timing light set back to zero...lol I also cut a hole above the pickup coil to see the angular position of the reluctor when ignition is triggered.

 

[basstrix]

Got a chance to repeat the rotor to distributor terminal phase test....this time with the timing light set to zero. The position of rotor looks great with and without vacuum advance applied....no need to adjust the phase, as far as I can tell. I thought I was on to something with the rotor phasing...the troubleshooting continues.



I also captured the reluctor to pickup coil trigger point, in case anyone can make use of the info. I'll also restate that reversing the polarity on the pickup coil has the effect of advancing timing by about 20 crankshaft degrees.

 

[Cleveland Crush]

Got a chance to repeat the rotor to distributor terminal phase test....this time with the timing light set to zero. The position of rotor looks great with and without vacuum advance applied....no need to adjust the phase, as far as I can tell. I thought I was on to something with the rotor phasing...the troubleshooting continues.

View attachment 92004

I also captured the reluctor to pickup coil trigger point, in case anyone can make use of the info. I'll also restate that reversing the polarity on the pickup coil has the effect of advancing timing by about 20 crankshaft degrees.

View attachment 92008

Excellent research & photos basstrix

 

[boilermaster]

basstrix,
are you running aftermarket fuel injection ?.
If so, perhaps you have some EMI..
Never known it to be an issue with carb and Duraspark.
if you are injected, might I recommend some 3M EMI tape on your pickup and tach signal wiring ?
Boilermaster

 

[basstrix]

basstrix,
are you running aftermarket fuel injection ?.
If so, perhaps you have some EMI..
Never known it to be an issue with carb and Duraspark.
if you are injected, might I recommend some 3M EMI tape on your pickup and tach signal wiring ?
Boilermaster

No EFI, but EMI was on my list, early on (before it was determined that the noise was directly related to vacuum advance). The oscilloscope showed an unusual pattern on the the power wire, so the alternator was disassembled and found a pair of blown diodes. The rectifier bridge was replaced....thought that would solve it. The charging system (the voltage at low RPM, in particular) improved drastically, but this issue with noise in the tach signal, remained.

The next step will be to have someone drive while I work the oscilloscope to see if I can see the noise on the scope waveform....maybe it's something to do with the DAQ.....the tachometer in the dash and the one on the column seem to function fine.

The one compelling characteristic is that the noise can be turned on and off by applying and removing vacuum to the advance canister.

Thanks for the input and stay tuned!

 

[Hemikiller]

Maybe try grounding the breaker plate. Pop a screw through the lug in the distributor harness, tie the other end to the block.