Rotor Phasing

[curts56]

I plan on using my Holley Sniper's ECU to control ignition timing. The trigger source will be a DSII distributor. If I lock the mechanical advance could I replace the vacuum advance with something like this to adjust rotor phasing?

https://www.speedwaymotors.com/HEI-External-Timing-Adjustment-Knob,1689.html

[drag-200stang]

Not sure that it fits a DS2 ...Why not lock it down in the right spot ? Cheaper and less weight and cut off the vacuum mount ears..Ok that might be too extreme.

[curts56]

Yeah, I didn't figure that one would fit a DSII, but I wanted to make sure I wasn't confused about rotor phasing and using the vacuum advance mechanism to make the phase adjustments. Locking it down is probably the simplest method. I just thought it might be nice to have some adjustable way to dial in the phasing.

[guhfluh]

Something like that wouldn't work to adjust the phasing like a normal adjustable rotor does. That moves the pickup plate, but the trigger wheel is still in the same relationship to the rotor, so the phasing stays the same, unless...since there's a way to adjust the spark offset in the software, once you turn the distributor, you can dial the timing offset back to match actual...still not sure, sorry.

My thought was to modify a stock rotor and shaft for adjustability and a set screw.

[sdiesel]

WTH, is rotor phasing?
with a crank trigger, and knock sensor the ecu will calibrate.
why do I not understand the need to set the rotor at a different clocking than the trigger wheel.
if that is indeed what is meant by phasing

[pmuller9]

WTH, is rotor phasing?
with a crank trigger, and knock sensor the ecu will calibrate.
why do I not understand the need to set the rotor at a different clocking than the trigger wheel.
if that is indeed what is meant by phasing

You want the rotor to point at the center of the contact in the distributor cap when the spark plug gap resistance is the highest which corresponds to the highest cylinder pressure.
For a N/A engine it may be 32 to 36 degrees BTDC.
For a forced induction engine it will be the timing at max boost.

I used to drill a 1/4" hole in the cap just behind the #1 plug wire tower and marker a line down the center of the rotor contact so I could check the phasing with a timing light.
When finished I covered the hole with a piece of electrical tape.

[drag-200stang]

He is still using the distributor to distribute the spark...You still want the rotor to line up with the cap terminal the best you can at the middle of the road timing or something like that ..You do not want it sparking between the terminals .
Oh I see ninja Paul beat me and did a better job of I too.

[curts56]

The pickup plate is relative to the electrodes in the cap and the rotor is relative to the trigger/reluctor wheel. Moving the pickup plate changes the relationship between the electrodes and the pickup. MSD has an adjustable rotor that changes the relationship between the rotor and the trigger wheel. Don't both methods affect the phasing?

[pmuller9]

The pickup plate is relative to the electrodes in the cap and the rotor is relative to the trigger/reluctor wheel. Moving the pickup plate changes the relationship between the electrodes and the pickup. MSD has an adjustable rotor that changes the relationship between the rotor and the trigger wheel. Don't both methods affect the phasing?

You are correct.
Repositioning the pickup plate changes the relationship between the pickup and the distributor housing and cap.
That in turn will determine where the rotor is when the pickup sends the trigger signal.

[sdiesel]

wow,

but is it necessary with modern electronic timing?
like TFI or Edis 6?.
and is this a
"the last one percent" of power to be wrung from an internal combuston engine.

makes perfect sense.

[pmuller9]

wow,

but is it necessary with modern electronic timing?
like TFI or Edis 6?.
and is this a
"the last one percent" of power to be wrung from an internal combuston engine.

makes perfect sense.

No, it is a different problem.
Sometimes when you are using an aftermarket EFI system that requires a specific offset the rotor ends up between terminals on the cap at the spark event so you need some way of correcting the alignment or "Phasing"

In the case of boosted applications you want the rotor at the center of the cap terminal at max boost to prevent spark blowout, decrease high voltage stress on the cap and most of all prevent crossover to another cylinder.

[Econoline]

I like the idea and simplicity of that device. I think one could be shope made for our distributors.

Bill Hamilton has written a couple of good articles on this that are pertinent to us. Distributor assembly may vary these being AMC DSII's.

http://www.binderplanet.com/forums/index.php?threads/amc-258-ds-distr-conversion.114800/#post-814271

http://www.binderplanet.com/forums/index.php?threads/amc-distributor-set-up.114498/

[curts56]

Those are good articles with lots of pictures.

[64 200 ranchero]

I have just adjusted my ds2's rotor phasing in order to use my programmable msd ignition. I locked out the mechanical advance and removed the vacuum advance. I then drilled a hole into the distributor cap @ cylinder #1 terminal and used a timing light to line up the rotor with the terminal by moving the arm of the vacuum advance lever. I then jb welded the plate into position.

[pmuller9]

I have just adjusted my ds2's rotor phasing in order to use my programmable msd ignition. I locked out the mechanical advance and removed the vacuum advance. I then drilled a hole into the distributor cap @ cylinder #1 terminal and used a timing light to line up the rotor with the terminal by moving the arm of the vacuum advance lever. I then jb welded the plate into position.

Nicely Done!

[curts56]

Good idea!

[drag-200stang]

It is probably not a problem but I do not now like the idea of moving the vacuum plate to get phase because the pickup to reluctor gap gets larger and less aligned as you advance the plate... On my ds2 a couple of degrees advanced seems to be best gap and alignment..Lock it down at the best gap..
I may be wrong but what is the best gap and alignment ? Check it out.
It seems that the msd adjustable rotor would be the best and easiest way,I assume it will fit our DS2 .

[curts56]

Does it fit? If so what part number?

[drag-200stang]

Does it fit? If so what part number?

NO, It looked to good to be true but I cannot find one that fits. Back to set screw on reluctor or original plan of moving vacuum advance plate..I think that it will work fine,just check that gap and alignment is ok.

[curts56]

Too bad . That would have been the easiest solution.